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atom.xml
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atom.xml
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<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
<title><![CDATA[T-Shaped Developer]]></title>
<link href="http://kylefdoherty.github.io/atom.xml" rel="self"/>
<link href="http://kylefdoherty.github.io/"/>
<updated>2015-01-04T22:49:28-05:00</updated>
<id>http://kylefdoherty.github.io/</id>
<author>
<name><![CDATA[Kyle Doherty]]></name>
</author>
<generator uri="http://octopress.org/">Octopress</generator>
<entry>
<title type="html"><![CDATA[Getting Started with JavaScript and Google Maps API]]></title>
<link href="http://kylefdoherty.github.io/blog/2014/07/17/getting-started-with-javascript-and-google-maps-api/"/>
<updated>2014-07-17T11:56:31-04:00</updated>
<id>http://kylefdoherty.github.io/blog/2014/07/17/getting-started-with-javascript-and-google-maps-api</id>
<content type="html"><![CDATA[<p>{Intro to what I did and how this blog post will mostly be code with comments & examples of what it looks like from codepen that you can then fork and play with it yourself.}</p>
<h2>Centering a Map</h2>
<p>The first thing you’re going to want to do is create a map object and set the center of the map and zoom level. The Google Maps API provides a nice <a href="https://developers.google.com/maps/documentation/javascript/examples/map-simple" target='_blank'>code sample</a> for making a simple map, which isn’t too difficult to figure out even if you’re a JS noob like me, but to really understand what everything was doing I commented out what each line of HTML & JS is doing.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
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<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
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<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
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<span class='line-number'>30</span>
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<span class='line-number'>43</span>
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<span class='line-number'>75</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="o"><!</span><span class="nx">DOCTYPE</span> <span class="nx">html</span><span class="o">></span>
</span><span class='line'><span class="o"><</span><span class="nx">html</span><span class="o">></span>
</span><span class='line'> <span class="o"><</span><span class="nx">head</span><span class="o">></span>
</span><span class='line'> <span class="o"><</span><span class="nx">meta</span> <span class="nx">name</span><span class="o">=</span><span class="s2">"viewport"</span> <span class="nx">content</span><span class="o">=</span><span class="s2">"initial-scale=1.0, user-scalable=no"</span> <span class="o">/></span>
</span><span class='line'> <span class="o"><</span><span class="nx">style</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"text/css"</span><span class="o">></span>
</span><span class='line'> <span class="cm">/* simple styling for the webpage and </span>
</span><span class='line'><span class="cm"> specifically the #map-canvas id */</span>
</span><span class='line'> <span class="nx">html</span> <span class="p">{</span> <span class="nx">height</span><span class="o">:</span> <span class="mi">100</span><span class="o">%</span> <span class="p">}</span>
</span><span class='line'> <span class="nx">body</span> <span class="p">{</span> <span class="nx">height</span><span class="o">:</span> <span class="mi">100</span><span class="o">%</span><span class="p">;</span> <span class="nx">margin</span><span class="o">:</span> <span class="mi">0</span><span class="p">;</span> <span class="nx">padding</span><span class="o">:</span> <span class="mi">0</span> <span class="p">}</span>
</span><span class='line'> <span class="err">#</span><span class="nx">map</span><span class="o">-</span><span class="nx">canvas</span> <span class="p">{</span> <span class="nx">height</span><span class="o">:</span> <span class="mi">100</span><span class="o">%</span> <span class="p">}</span> <span class="cm">/*BE SURE TO - set the</span>
</span><span class='line'><span class="cm"> height of the map-canvas div */</span>
</span><span class='line'> <span class="o"><</span><span class="err">/style></span>
</span><span class='line'> <span class="o"><</span><span class="nx">script</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"text/javascript"</span>
</span><span class='line'> <span class="cm">/*uses the google maps api with your api key, </span>
</span><span class='line'><span class="cm"> https://developers.google.com/maps/documentation/</span>
</span><span class='line'><span class="cm"> javascript/tutorial#api_key*/</span>
</span><span class='line'> <span class="nx">src</span><span class="o">=</span><span class="s2">"https://maps.googleapis.com/maps/api/js?key=API_KEY"</span><span class="o">></span>
</span><span class='line'> <span class="o"><</span><span class="err">/script></span>
</span><span class='line'> <span class="o"><</span><span class="nx">script</span> <span class="nx">type</span><span class="o">=</span><span class="s2">"text/javascript"</span><span class="o">></span>
</span><span class='line'> <span class="c1">// creates the funtion initialize which is called at the bottom of the script.</span>
</span><span class='line'> <span class="kd">function</span> <span class="nx">initialize</span><span class="p">()</span> <span class="p">{</span>
</span><span class='line'> <span class="cm">/*creates a mapOptions object literal with a center</span>
</span><span class='line'><span class="cm"> and zoom level. A JS object literal looks a lot like </span>
</span><span class='line'><span class="cm"> a hash in Ruby. Here is a blog post describing the</span>
</span><span class='line'><span class="cm"> difference, http://stantona.github.io/blog/2012/12/12/a</span>
</span><span class='line'><span class="cm"> -tale-of-two-object-models-javascript-and-ruby/*/</span>
</span><span class='line'> <span class="kd">var</span> <span class="nx">mapOptions</span> <span class="o">=</span> <span class="p">{</span>
</span><span class='line'> <span class="cm">/*the center key sets the center of the map to the</span>
</span><span class='line'><span class="cm"> specified latitude and longitude. It's currently set</span>
</span><span class='line'><span class="cm"> to be centered on Manhattan*/</span>
</span><span class='line'> <span class="nx">center</span><span class="o">:</span> <span class="k">new</span> <span class="nx">google</span><span class="p">.</span><span class="nx">maps</span><span class="p">.</span><span class="nx">LatLng</span><span class="p">(</span><span class="mf">40.7903</span><span class="p">,</span> <span class="o">-</span><span class="mf">73.9597</span><span class="p">),</span>
</span><span class='line'> <span class="cm">/*zoom key sets how zoomed in or out you are, with 0</span>
</span><span class='line'><span class="cm"> being the farthest zoomed out and 20 being the </span>
</span><span class='line'><span class="cm"> most zoomed in*/</span>
</span><span class='line'> <span class="nx">zoom</span><span class="o">:</span> <span class="mi">8</span>
</span><span class='line'> <span class="p">};</span> <span class="c1">//end of var mapOptions</span>
</span><span class='line'>
</span><span class='line'> <span class="cm">/*sets the var map to a new instance of a google map </span>
</span><span class='line'><span class="cm"> and injects it in the div with id="map-canvas".</span>
</span><span class='line'><span class="cm"> It sets the center and zoom of the new map to the</span>
</span><span class='line'><span class="cm"> mapOptions object literal defined above*/</span>
</span><span class='line'> <span class="kd">var</span> <span class="nx">map</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">google</span><span class="p">.</span><span class="nx">maps</span><span class="p">.</span><span class="nx">Map</span><span class="p">(</span><span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s2">"map-canvas"</span><span class="p">),</span>
</span><span class='line'> <span class="nx">mapOptions</span><span class="p">);</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="cm">/*using the event addDomListenever to call the </span>
</span><span class='line'><span class="cm"> initialize method. this is similar to the</span>
</span><span class='line'><span class="cm"> addEventListener method. we tell the </span>
</span><span class='line'><span class="cm"> addDomListener which DOM element to use</span>
</span><span class='line'><span class="cm"> (window in this case), what event to listen </span>
</span><span class='line'><span class="cm"> for (load), and which method to call after </span>
</span><span class='line'><span class="cm"> the event has occurred.*/</span>
</span><span class='line'>
</span><span class='line'> <span class="cm">/*For more info on the DOM check out this video </span>
</span><span class='line'><span class="cm"> series on the DOM, https://www.youtube.</span>
</span><span class='line'><span class="cm"> com/playlist?list=PL18600E7CA651B16B and this </span>
</span><span class='line'><span class="cm"> Mozilla article on event listeners, https://developer.</span>
</span><span class='line'><span class="cm"> mozilla.org/en-US/docs/Web/API/EventTarget.</span>
</span><span class='line'><span class="cm"> addEventListener*/</span>
</span><span class='line'>
</span><span class='line'> <span class="nx">google</span><span class="p">.</span><span class="nx">maps</span><span class="p">.</span><span class="nx">event</span><span class="p">.</span><span class="nx">addDomListener</span><span class="p">(</span><span class="nb">window</span><span class="p">,</span> <span class="s1">'load'</span><span class="p">,</span> <span class="nx">initialize</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="cm">/*finally to really rip through what is going on here</span>
</span><span class='line'><span class="cm"> and what other things you can do such as asynchronously</span>
</span><span class='line'><span class="cm"> loading the API visit the Google maps getting started </span>
</span><span class='line'><span class="cm"> doc, https://developers.google.</span>
</span><span class='line'><span class="cm"> com/maps/documentation/javascript/tutorial*/</span>
</span><span class='line'>
</span><span class='line'> <span class="o"><</span><span class="err">/script></span>
</span><span class='line'> <span class="o"><</span><span class="err">/head></span>
</span><span class='line'> <span class="o"><</span><span class="nx">body</span><span class="o">></span>
</span><span class='line'> <span class="c"><!--</span> <span class="nx">creates</span> <span class="nx">a</span> <span class="nx">div</span> <span class="k">for</span> <span class="nx">the</span> <span class="nx">map</span> <span class="nx">canvas</span> <span class="nx">to</span> <span class="nx">be</span> <span class="nx">injected</span> <span class="nx">into</span> <span class="nx">on</span> <span class="nx">the</span> <span class="nx">html</span> <span class="nx">page</span> <span class="o">--></span>
</span><span class='line'> <span class="o"><</span><span class="nx">div</span> <span class="nx">id</span><span class="o">=</span><span class="s2">"map-canvas"</span><span class="o">/></span>
</span><span class='line'> <span class="o"><</span><span class="err">/body></span>
</span><span class='line'><span class="o"><</span><span class="err">/html></span>
</span></code></pre></td></tr></table></div></figure>
<h2>Dropping a Pen the Map</h2>
<figure class='code'><figcaption><span>Coffeescript Tricks start:51 mark:52,54-55</span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='coffeescript'><span class='line'><span class="c1"># Given an alphabet:</span>
</span><span class='line'><span class="nv">alphabet = </span><span class="s">'abcdefghijklmnopqrstuvwxyz'</span>
</span><span class='line'>
</span><span class='line'><span class="c1"># Iterate over part of the alphabet:</span>
</span><span class='line'><span class="nx">console</span><span class="p">.</span><span class="nx">log</span> <span class="nx">letter</span> <span class="k">for</span> <span class="nx">letter</span> <span class="k">in</span> <span class="nx">alphabet</span><span class="p">[</span><span class="mi">4</span><span class="p">..</span><span class="mi">8</span><span class="p">]</span>
</span></code></pre></td></tr></table></div></figure>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Getting and Parsing the Citi Bike JSON Feed with HTTParty]]></title>
<link href="http://kylefdoherty.github.io/blog/2014/06/30/getting-and-parsing-the-citi-bike-json-feed-with-httparty/"/>
<updated>2014-06-30T22:02:46-04:00</updated>
<id>http://kylefdoherty.github.io/blog/2014/06/30/getting-and-parsing-the-citi-bike-json-feed-with-httparty</id>
<content type="html"><![CDATA[<h2>BigIdeas Citi Bike Finder Challenge</h2>
<p>For our Flatiron School Meetup Presentation, <a href="http://amyrjohnson.github.io/" target="_blank">Amy Johnson</a> and I are trying to tackle at least part of one of NYCBigApps’ BigIdeas Challenges posted by Citi Bike, <a href="http://citibikefinder.splashthat.com/" target="_blank"><a href="http://citibikefinder.splashthat.com/">http://citibikefinder.splashthat.com/</a></a>. The main problem they outline is that during high commute times people often find themselves being “dockblocked” or “bluebiked”, as the <a href="http://gothamist.com/2013/06/27/citibike_fail_dumbo_totally_dockblo.php" target="_blank">Gothamist put it</a>, because there aren’t any available spaces to deposit their bike.</p>
<p>The main idea for a solution is to have some sort of suggestion app for starting and ending locations with estimated availability based on historical data. There are some other features they have on their wishlist for the app, but we figure this alone is about all we want to try to bite off for the moment.</p>
<h2>Our Potential Solution</h2>
<p>Obviously the first thing we need to figure out is, is what data is available to us. It seems, for the moment at least, that there isn’t historical data on bike dock stations readily available to us (we’ve reached out and are waiting to hear back on this), so for the time being it looks like we’ll potentially need to hit the real time <a href="http://www.citibikenyc.com/stations/json" target="_blank">JSON feed</a>, and gather data that way. Plus even if there is historical data we can get we still may want to collect our own and we’ll definitely want to be grabbing data about station’s current available bikes and docks, if they’re in service, etc.</p>
<h2>It’s a HTTParty</h2>
<p>The first to do then is figure out how to get and parse this JSON feed. JSON by the way stands for <a href="http://en.wikipedia.org/wiki/JSON" target="_blank">JavaScript Object Notation</a> and gives you back data in attribute-value pairs…basically a hash. After a quick search on the Google I found the HTTParty gem, which is a HTTP client gem that allows you to easily make HTTP requests as well as automatically parses JSON or XML responses you get back.</p>
<h2>Ok down to business…Parsing the Citi Bike Feed.</h2>
<p>This is super simple with HTTParty. All you have to do is require the gem and then use <code>HTTParty.get(“the_url”)</code>, and if you stick pry in your file it becomes super duper easy to play with the <code>HTTParty::Response</code> object that is returned to you.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="nb">require</span> <span class="s1">'httparty'</span>
</span><span class='line'><span class="nb">require</span> <span class="s1">'pry'</span>
</span><span class='line'>
</span><span class='line'>
</span><span class='line'><span class="n">response</span> <span class="o">=</span> <span class="no">HTTParty</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s2">"http://www.citibikenyc.com/stations/json"</span><span class="p">)</span>
</span><span class='line'>
</span><span class='line'><span class="nb">binding</span><span class="o">.</span><span class="n">pry</span>
</span></code></pre></td></tr></table></div></figure>
<p>What you get back is technically, as mentioned, a <code>HTTParty::Response</code> object, but really it’s a hash. So if we call <code>.keys</code> on it we can see what keys it has.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">response</span><span class="o">.</span><span class="n">keys</span>
</span><span class='line'><span class="c1"># => ["executionTime", "stationBeanList"]</span>
</span></code></pre></td></tr></table></div></figure>
<p>My guess is “stationBeanList” is what we want and sure enough it gives us back a big array of 332 station hashes.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">response</span><span class="o">[</span><span class="s2">"stationBeanList"</span><span class="o">]</span>
</span><span class='line'>
</span><span class='line'><span class="c1"># => [{"id"=>72,</span>
</span><span class='line'> <span class="c1"># "stationName"=>"W 52 St & 11 Ave",</span>
</span><span class='line'> <span class="c1"># "availableDocks"=>19,</span>
</span><span class='line'> <span class="c1"># "totalDocks"=>38,</span>
</span><span class='line'> <span class="c1"># "latitude"=>40.76727216,</span>
</span><span class='line'> <span class="c1"># "longitude"=>-73.99392888,</span>
</span><span class='line'> <span class="c1"># "statusValue"=>"In Service",</span>
</span><span class='line'> <span class="c1"># "statusKey"=>1,</span>
</span><span class='line'> <span class="c1"># "availableBikes"=>13,</span>
</span><span class='line'> <span class="c1"># "stAddress1"=>"W 52 St & 11 Ave",</span>
</span><span class='line'> <span class="c1"># "stAddress2"=>"",</span>
</span><span class='line'> <span class="c1"># "city"=>"",</span>
</span><span class='line'> <span class="c1"># "postalCode"=>"",</span>
</span><span class='line'> <span class="c1"># "location"=>"",</span>
</span><span class='line'> <span class="c1"># "altitude"=>"",</span>
</span><span class='line'> <span class="c1"># "testStation"=>false,</span>
</span><span class='line'> <span class="c1"># "lastCommunicationTime"=>nil,</span>
</span><span class='line'> <span class="c1"># "landMark"=>""},</span>
</span><span class='line'> <span class="c1"># {"id"=>79,</span>
</span><span class='line'> <span class="c1"># "stationName"=>"Franklin St & W Broadway",</span>
</span><span class='line'> <span class="c1"># "availableDocks"=>32,</span>
</span><span class='line'> <span class="c1"># "totalDocks"=>33,</span>
</span><span class='line'> <span class="c1"># "latitude"=>40.71911552,</span>
</span><span class='line'> <span class="c1"># "longitude"=>-74.00666661,</span>
</span><span class='line'> <span class="c1"># "statusValue"=>"In Service",</span>
</span><span class='line'> <span class="c1"># "statusKey"=>1,</span>
</span><span class='line'> <span class="c1"># "availableBikes"=>1,</span>
</span><span class='line'> <span class="c1"># .....</span>
</span></code></pre></td></tr></table></div></figure>
<p>From here it’s easy to grab specific data out of this array of stations. For example, the stations whose “statusKey” does not equal 1 since that probably will mean they’re not in service and might show me the other possible status keys.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">response</span><span class="o">[</span><span class="s2">"stationBeanList"</span><span class="o">].</span><span class="n">select</span> <span class="p">{</span><span class="o">|</span><span class="n">station</span><span class="o">|</span> <span class="n">station</span><span class="o">[</span><span class="s2">"statusKey"</span><span class="o">]</span> <span class="o">!=</span> <span class="mi">1</span><span class="p">}}</span>
</span><span class='line'>
</span><span class='line'> <span class="c1"># => returns array of 5 station hashes with “statusKey” => 3 and “statusValue” => “Not in Service</span>
</span></code></pre></td></tr></table></div></figure>
<p>Or let’s say we want to see the stations that have over 50 docks i.e the big ass docks in the city.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'> <span class="n">big_ass_docks</span> <span class="o">=</span> <span class="n">response</span><span class="o">[</span><span class="s2">"stationBeanList"</span><span class="o">].</span><span class="n">select</span> <span class="p">{</span><span class="o">|</span><span class="n">station</span><span class="o">|</span> <span class="n">station</span><span class="o">[</span><span class="s2">"totalDocks"</span><span class="o">]</span> <span class="o">>=</span> <span class="mi">50</span><span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="c1"># => An array of 32 station hashes </span>
</span></code></pre></td></tr></table></div></figure>
<h2>Next Steps</h2>
<p>Getting the JSON feed and parsing it was way simpler than I had imagined. From here we need to figure out what our absolute bare bones app needs to do and then plan from there. We can also for sure create a Station class and generate a bunch of Station objects from the stations array. This way anytime we hit the JSON feed we can have these objects update their attributes.</p>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Close Reading Code]]></title>
<link href="http://kylefdoherty.github.io/blog/2014/06/26/close-reading-code/"/>
<updated>2014-06-26T08:38:53-04:00</updated>
<id>http://kylefdoherty.github.io/blog/2014/06/26/close-reading-code</id>
<content type="html"><![CDATA[<h2>TL;DR</h2>
<p><strong>If you’re a rookie programmer like me your programming level is here:</strong>
<br>
<img class="center" src="http://kylefdoherty.github.io/images/baby.jpg">
<strong>And you want to be at this level:</strong>
<br>
<img class="center" src="http://kylefdoherty.github.io/images/ironic.jpg"></p>
<p><strong>Use <a href="http://writingcenter.fas.harvard.edu/pages/how-do-close-reading" target="_blank">close reading techniques</a> to level up your coding skills.</strong></p>
<h2>Learning to Code Well == Learning to Write Well</h2>
<p>When I decided I wanted to become a programmer back in January I spent a lot of time thinking about the act of learning and what were the best ways to learn to program. This meant I also spent a lot of time researching the topic on the interwebs and the advice I kept coming across was, <strong>“you need to write a lot of code and read even more.”</strong> This is when I started forcing myself to read other people’s code.</p>
<p>Then at the start of Flatiron School, Avi (the dean) described our coding ability one day as “Baby Talk.” I thought this was a fair metaphor, but it also made me think about how learning to code well is like learning to write well. One of the best ways to improve your writing skills is to use a technique called close reading, which transfers nicely to learning to program.</p>
<h2>WTF is Close Reading</h2>
<p><a href="http://writingcenter.fas.harvard.edu/pages/how-do-close-reading" target="_blank">Close reading</a> is defined by <a href="http://en.wikipedia.org/wiki/Close_reading"target="_blank">wikipedia</a> as, “the careful, sustained interpretation of a brief passage of text. Such a reading places great emphasis on the single particular over the general, paying close attention to individual words, syntax, and the order in which sentences and ideas unfold as they are read.”</p>
<p><img class="center" src="http://kylefdoherty.github.io/images/close_reading.JPG"></p>
<p>Often close reading is used to better understand an academic text so you can compose an essay about it. However, it can also be used to improve your reading and writing skills, because you’re paying close attention to vocabulary, sentence structure, style, etc. and begin to incorporate this into your own writing. This technique was especially helpful for me while studying in Chile and having to read academic papers in Spanish on topics such as the 1973 Arab–Israeli War and Business Operations. At the time my Spanish was at a 7th grade level at best and these papers were 12 grade plus. Thus, I spent a ton of time meticulously going through my assigned readings with pen, highlighter and Google to breakdown complex sentences, lookup words I didn’t know, and take notes detailed notes. This paid huge dividends down the road, helping me level up on my Spanish reading and writing skills…not that I still have them, but hey I did at one time.</p>
<h2>How to Close Read Code</h2>
<p>The way I close read code is similar to how I read an academic paper, except instead of paper and pen, I use my text editor and IRB. While I’m reading through complex code I write comments above or next to each line, explaining in detail what is going on. And if I don’t understand what’s going on I just look it up in the Doc, throw it in IRB or use Pry, or I go to the Google. With one or a combo of these you should be able to figure out what’s goign on.</p>
<p>Here’s an example of my detailed comments for a section of a Student class from a recent Flatiron lab:</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
<span class='line-number'>31</span>
<span class='line-number'>32</span>
<span class='line-number'>33</span>
<span class='line-number'>34</span>
<span class='line-number'>35</span>
<span class='line-number'>36</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="k">class</span> <span class="nc">Student</span>
</span><span class='line'> <span class="c1">#setting the attributes of the student class to a class instance variable </span>
</span><span class='line'> <span class="no">ATTRIBUTES</span> <span class="o">=</span> <span class="p">{</span>
</span><span class='line'> <span class="ss">:id</span> <span class="o">=></span> <span class="s2">"INTEGER PRIMARY KEY"</span><span class="p">,</span>
</span><span class='line'> <span class="ss">:name</span> <span class="o">=></span> <span class="s2">"TEXT"</span><span class="p">,</span>
</span><span class='line'> <span class="ss">:tagline</span> <span class="o">=></span> <span class="s2">"TEXT"</span><span class="p">,</span>
</span><span class='line'> <span class="ss">:github</span> <span class="o">=></span> <span class="s2">"TEXT"</span><span class="p">,</span>
</span><span class='line'> <span class="ss">:twitter</span> <span class="o">=></span> <span class="s2">"TEXT"</span><span class="p">,</span>
</span><span class='line'> <span class="ss">:blog_url</span> <span class="o">=></span> <span class="s2">"TEXT"</span><span class="p">,</span>
</span><span class='line'> <span class="ss">:image_url</span> <span class="o">=></span> <span class="s2">"TEXT"</span><span class="p">,</span>
</span><span class='line'> <span class="ss">:biography</span> <span class="o">=></span> <span class="s2">"TEXT"</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="c1"># ATTRIBUTES.keys.each do |attribute|</span>
</span><span class='line'> <span class="c1"># attr_accessor attribute</span>
</span><span class='line'> <span class="c1"># end</span>
</span><span class='line'>
</span><span class='line'> <span class="c1">#creating the attr_accessor by taking the keys from the ATTRIBUTES hash</span>
</span><span class='line'> <span class="c1">#which returns an array and sending that array to the attr_accessor </span>
</span><span class='line'> <span class="c1">#method with the splat operator. This 'explodes' the array into individual </span>
</span><span class='line'> <span class="c1">#elements which are passed to the method</span>
</span><span class='line'> <span class="kp">attr_accessor</span> <span class="o">*</span><span class="no">ATTRIBUTES</span><span class="o">.</span><span class="n">keys</span>
</span><span class='line'>
</span><span class='line'> <span class="c1">#creates an empty students table by creating a SQL statment </span>
</span><span class='line'> <span class="c1">#and assigning it to a variable and then passing that sql var to </span>
</span><span class='line'> <span class="c1">#DB[:conn].execute. Inside the CREATE TABLE block</span>
</span><span class='line'> <span class="c1">#the method .schema_defininition is being called in order to insert the </span>
</span><span class='line'> <span class="c1">#correct columns in the table (see schema definition below for explination)</span>
</span><span class='line'> <span class="k">def</span> <span class="nc">self</span><span class="o">.</span><span class="nf">create_table</span>
</span><span class='line'> <span class="n">sql</span> <span class="o">=</span> <span class="o"><<-</span><span class="no">SQL</span>
</span><span class='line'><span class="sh"> CREATE TABLE IF NOT EXISTS #{self.table_name} (</span>
</span><span class='line'><span class="sh"> #{schema_definition} </span>
</span><span class='line'><span class="sh"> )</span>
</span><span class='line'><span class="no"> SQL</span>
</span><span class='line'> <span class="no">DB</span><span class="o">[</span><span class="ss">:conn</span><span class="o">].</span><span class="n">execute</span><span class="p">(</span><span class="n">sql</span><span class="p">)</span>
</span><span class='line'> <span class="k">end</span>
</span></code></pre></td></tr></table></div></figure>
<p>(All the <a href="https://gist.github.com/kylefdoherty/3f16da77103ff13b4c4d" target="_blank">code</a> for the Student class)</p>
<p>As you can see I try to explain exactly what is going on in detail so I’m aboslutely sure what’s going on.</p>
<h2>Use the Code You Read</h2>
<p>After you’ve read through and commented out what each line of code is doing, don’t stop there. I like to play with what I’ve learned in IRB to help me internalize it or rebuild it on my own.</p>
<p>For example, a week before Flatiron School started I learned a bit of Javascript and decided to try building a countdown to the first day of school. Google led me to this <a href"http://blog.smalldo.gs/2013/12/create-simple-countdown/" target="_blank">tutorial</a> which I disected line by line with comments for what was goign on.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="o"><</span><span class="nx">h1</span> <span class="nx">id</span><span class="o">=</span><span class="s1">'countdown-holder'</span><span class="o">></span><span class="nx">Coutndown</span> <span class="nx">goes</span> <span class="nx">here</span><span class="o">!<</span><span class="err">/h1> </span>
</span><span class='line'>
</span><span class='line'><span class="c"><!--</span> <span class="nx">creating</span> <span class="nx">an</span> <span class="nx">h1</span> <span class="nx">tag</span> <span class="nx">wtih</span> <span class="nx">the</span> <span class="nx">id</span> <span class="s1">'countdown-holder'</span>
</span><span class='line'><span class="nx">so</span> <span class="nx">it</span> <span class="nx">can</span> <span class="nx">be</span> <span class="nx">targeted</span> <span class="nx">by</span> <span class="nx">JS</span> <span class="kd">with</span> <span class="nx">the</span> <span class="p">.</span><span class="nx">getElementById</span> <span class="nx">method</span><span class="o">--></span>
</span><span class='line'>
</span><span class='line'><span class="o"><</span><span class="nx">script</span> <span class="nx">src</span><span class="o">=</span><span class="s2">"http://smalldo.gs/js/countdown.min.js"</span><span class="o">><</span><span class="err">/script> </span>
</span><span class='line'>
</span><span class='line'> <span class="c"><!--</span> <span class="nx">including</span> <span class="nx">the</span> <span class="nx">countdown</span><span class="p">.</span><span class="nx">js</span> <span class="nx">script</span><span class="o">--></span>
</span><span class='line'>
</span><span class='line'><span class="o"><</span><span class="nx">script</span><span class="o">></span>
</span><span class='line'> <span class="kd">var</span> <span class="nx">clock</span> <span class="o">=</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s2">"countdown-holder"</span><span class="p">)</span>
</span><span class='line'>
</span><span class='line'> <span class="c1">//setting a variable named clock to 'document.getElementById' which is the method .getElementById being called on the 'document' (the html file). The id we're telling it to get is "countdown-holder"</span>
</span><span class='line'>
</span><span class='line'> <span class="p">,</span> <span class="nx">targetDate</span> <span class="o">=</span> <span class="k">new</span> <span class="nb">Date</span><span class="p">(</span><span class="mi">2014</span><span class="p">,</span><span class="mi">05</span><span class="p">,</span><span class="mi">02</span><span class="p">,</span><span class="mi">09</span><span class="p">,</span><span class="mi">00</span><span class="p">,</span><span class="mi">00</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="c1">//setting a var named targetDate to a new date object with the date of June 2, 2015 at 9:00 am</span>
</span><span class='line'>
</span><span class='line'> <span class="nx">clock</span><span class="p">.</span><span class="nx">innerHTML</span> <span class="o">=</span> <span class="nx">countdown</span><span class="p">(</span><span class="nx">targetDate</span><span class="p">).</span><span class="nx">toString</span><span class="p">();</span>
</span><span class='line'>
</span><span class='line'> <span class="c1">// calling the .innerHTML method on clock to replace the h1 text with the countdown targetDate converted to a string</span>
</span><span class='line'>
</span><span class='line'> <span class="nx">setInterval</span><span class="p">(</span><span class="kd">function</span><span class="p">(){</span>
</span><span class='line'> <span class="nx">clock</span><span class="p">.</span><span class="nx">innerHTML</span> <span class="o">=</span> <span class="nx">countdown</span><span class="p">(</span><span class="nx">targetDate</span><span class="p">).</span><span class="nx">toString</span><span class="p">();</span>
</span><span class='line'> <span class="p">}),</span> <span class="mi">1000</span><span class="p">;</span>
</span><span class='line'>
</span><span class='line'> <span class="c1">// the setInterval method executes a function over and over again, at specified time intervals. Here we're resetting the clock.innerHTML variable every second (1000 milliseconds in a second)</span>
</span><span class='line'>
</span><span class='line'><span class="o"><</span><span class="err">/script></span>
</span></code></pre></td></tr></table></div></figure>
<p>After getting a good understanding of what was going on, I tried coding it by myself and got this:</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="o"><</span><span class="nx">script</span> <span class="nx">src</span><span class="o">=</span><span class="s2">"http://smalldo.gs/js/countdown.min.js"</span><span class="o">><</span><span class="err">/script> </span>
</span><span class='line'>
</span><span class='line'> <span class="o"><</span><span class="nx">h1</span><span class="o">></span><span class="nx">Flatiron</span> <span class="nx">Ruby005</span> <span class="nx">Countdown</span><span class="o"><</span><span class="err">/h1></span>
</span><span class='line'> <span class="o"><</span><span class="nx">h2</span> <span class="nx">id</span><span class="o">=</span><span class="s1">'countdown-holder'</span><span class="o">></span><span class="nx">Countdown</span> <span class="nx">goes</span> <span class="nx">here</span><span class="o">!<</span><span class="err">/h2> </span>
</span><span class='line'>
</span><span class='line'>
</span><span class='line'><span class="o"><</span><span class="nx">script</span><span class="o">></span>
</span><span class='line'> <span class="kd">var</span> <span class="nx">endDate</span> <span class="o">=</span> <span class="k">new</span> <span class="nb">Date</span><span class="p">(</span><span class="mi">2014</span><span class="p">,</span><span class="mi">05</span><span class="p">,</span><span class="mi">02</span><span class="p">,</span><span class="mi">09</span><span class="p">,</span><span class="mi">00</span><span class="p">,</span><span class="mi">00</span><span class="p">);</span>
</span><span class='line'> <span class="kd">var</span> <span class="nx">timeSpan</span> <span class="o">=</span> <span class="nx">countdown</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span> <span class="nx">endDate</span> <span class="p">);</span>
</span><span class='line'> <span class="kd">var</span> <span class="nx">clock</span> <span class="o">=</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s2">"countdown-holder"</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="kd">var</span> <span class="nx">timer</span> <span class="o">=</span> <span class="nx">setInterval</span><span class="p">(</span><span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
</span><span class='line'> <span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="nx">timeSpan</span> <span class="o">=</span> <span class="nx">countdown</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span> <span class="nx">endDate</span> <span class="p">));</span>
</span><span class='line'> <span class="k">if</span><span class="p">(</span><span class="nx">timeSpan</span> <span class="o"><</span> <span class="mi">1</span><span class="p">)</span>
</span><span class='line'> <span class="p">{</span>
</span><span class='line'> <span class="nx">clearInterval</span><span class="p">(</span><span class="nx">timer</span><span class="p">);</span> <span class="c1">// need to find a way to set timespan at the global level so even after someone refreshes the page the timer doesn't run and the new clock text appears</span>
</span><span class='line'>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'> <span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="nx">clock</span><span class="p">.</span><span class="nx">innerHTML</span> <span class="o">=</span> <span class="nx">countdown</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span> <span class="nx">endDate</span> <span class="p">).</span><span class="nx">toString</span><span class="p">());</span>
</span><span class='line'> <span class="p">},</span><span class="mi">1000</span><span class="p">);</span>
</span><span class='line'><span class="o"><</span><span class="err">/script></span>
</span></code></pre></td></tr></table></div></figure>
<p>This got me close to a working countdown script but wasn’t quite working. With a little help from <a href="https://twitter.com/ttsiege" target="_blank">Tristen</a> I was able to refactor my code and get it working.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
</pre></td><td class='code'><pre><code class='javascript'><span class='line'><span class="o"><</span><span class="nx">script</span> <span class="nx">src</span><span class="o">=</span><span class="s2">"http://smalldo.gs/js/countdown.min.js"</span><span class="o">><</span><span class="err">/script> </span>
</span><span class='line'>
</span><span class='line'> <span class="o"><</span><span class="nx">h1</span><span class="o">></span><span class="nx">Flatiron</span> <span class="nx">Ruby005</span> <span class="nx">Countdown</span><span class="o"><</span><span class="err">/h1></span>
</span><span class='line'> <span class="o"><</span><span class="nx">h2</span> <span class="nx">id</span><span class="o">=</span><span class="s1">'countdown-holder'</span><span class="o">></span><span class="nx">Countdown</span> <span class="nx">goes</span> <span class="nx">here</span><span class="o">!<</span><span class="err">/h2> </span>
</span><span class='line'>
</span><span class='line'><span class="o"><</span><span class="nx">script</span><span class="o">></span>
</span><span class='line'>
</span><span class='line'> <span class="kd">var</span> <span class="nx">timer</span> <span class="o">=</span> <span class="nx">setInterval</span><span class="p">(</span><span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
</span><span class='line'> <span class="kd">var</span> <span class="nx">endDate</span> <span class="o">=</span> <span class="k">new</span> <span class="nb">Date</span><span class="p">(</span><span class="mi">2014</span><span class="p">,</span><span class="mi">05</span><span class="p">,</span><span class="mi">02</span><span class="p">,</span><span class="mi">09</span><span class="p">,</span><span class="mi">00</span><span class="p">,</span><span class="mi">00</span><span class="p">),</span>
</span><span class='line'> <span class="nx">clock</span> <span class="o">=</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s2">"countdown-holder"</span><span class="p">),</span>
</span><span class='line'> <span class="nx">gif</span> <span class="o">=</span> <span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s2">"gif"</span><span class="p">),</span>
</span><span class='line'> <span class="nx">timeSpan</span> <span class="o">=</span> <span class="nx">countdown</span><span class="p">(</span><span class="kc">null</span><span class="p">,</span> <span class="nx">endDate</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'> <span class="c1">// breaks recursion</span>
</span><span class='line'> <span class="k">if</span><span class="p">(</span><span class="nx">timeSpan</span><span class="p">.</span><span class="nx">value</span> <span class="o"><</span> <span class="mi">1</span><span class="p">)</span>
</span><span class='line'> <span class="p">{</span>
</span><span class='line'> <span class="nx">clearInterval</span><span class="p">(</span><span class="nx">timer</span><span class="p">);</span> <span class="c1">// need to find a way to set timespan at the global level so even after someone refreshes the page the timer doesn't run and the new clock text appears</span>
</span><span class='line'> <span class="k">return</span> <span class="nx">clock</span><span class="p">.</span><span class="nx">innerHTML</span> <span class="o">=</span> <span class="s2">"Flatiron Ruby005 Has Begun!"</span>
</span><span class='line'> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'> <span class="nx">clock</span><span class="p">.</span><span class="nx">innerHTML</span> <span class="o">=</span> <span class="nx">timeSpan</span><span class="p">.</span><span class="nx">toString</span><span class="p">();</span>
</span><span class='line'>
</span><span class='line'> <span class="p">},</span><span class="mi">1000</span><span class="p">);</span>
</span><span class='line'>
</span><span class='line'>
</span><span class='line'><span class="o"><</span><span class="err">/script></span>
</span></code></pre></td></tr></table></div></figure>
<p>Close reading the original countdown code and then recoding it myself helped me grasp on a much deeper level how to declare JS variables, JS functions & function scope, and JS conventions, such as declaring multiple variables at once.</p>
<h2>Final Thoughts</h2>
<p>I know for me forcing myself to take the time to close read code is something I still struggle with, but I can honestly say this has helped me improve my code substantially. If you take the time to read code line by line, add detailed comments explaining what’s going on, and then use it, it will pay off huge down the road.</p>
<h2>Resources on Learning & Learning to Program I like</h2>
<ul>
<li><p><a href="http://rubyrogues.com/131-rr-how-to-learn/" target="_blank">Ruby Rogues 131 - How to Learn</a></p></li>
<li><p><a href="http://www.uvm.edu/~pdodds/files/papers/others/2007/ericsson2007a.pdf" target="_blank">HBR - The Making of an Expert</a></p></li>
<li><p><a href="http://www.gamedev.net/blog/355/entry-2250592-become-a-good-programmer-in-six-really-hard-steps/" target="_blank">Become a Good Programmer in Six Really Hard Steps</a></p></li>
<li><p><a href="http://catgrena.de/careers/2013/10/15/standing-out-from-the-crowd.html" target="_blank">Standing Our From the Crowd</a></p></li>
<li><p><a href="http://rubyrogues.com/159-rr-hacking-education-with-saron-yitbarek/" target="_blank">Ruby Rogues 159 - Hacking Education with Saron Yitbarek (Flatiron School Alum)</a></p></li>
<li><p><a href="https://www.youtube.com/watch?v=mW_xKGUKLpk" target="_blank">Reading Code Good - Saron’s RailsConf2014 Talk</a></p></li>
</ul>
]]></content>
</entry>
<entry>
<title type="html"><![CDATA[Ruby Inject Basics]]></title>
<link href="http://kylefdoherty.github.io/blog/2014/06/13/ruby-inject-basics/"/>
<updated>2014-06-13T00:06:01-04:00</updated>
<id>http://kylefdoherty.github.io/blog/2014/06/13/ruby-inject-basics</id>
<content type="html"><![CDATA[<p>This week during lecture at Flatiron school, <a href="https://twitter.com/aviflombaum" target="_blank">Avi</a> showed us Ruby’s <code>.inject</code> method (also known as .reduce). I thought this seemed like a pretty cool and potentially powerful method and decided to do a bit more research so I could start using it with confidence in my code.</p>
<h2>How Inject Works</h2>
<p><code>.inject</code> is an iterator method (technically an enumerable method) that creates an accumulator variable that “accumulates” whatever you want as you iterate over some sort of collection and returns the accumulator when the iteration is complete.</p>
<p>Instead of trying to explain further let’s take a peek at a simple example.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="o">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="o">].</span><span class="n">inject</span> <span class="k">do</span> <span class="o">|</span><span class="n">accumulator</span><span class="p">,</span> <span class="n">element</span><span class="o">|</span>
</span><span class='line'>
</span><span class='line'> <span class="nb">puts</span> <span class="s2">"accumulator: </span><span class="si">#{</span><span class="n">accumulator</span><span class="si">}</span><span class="s2">, element: </span><span class="si">#{</span><span class="n">element</span><span class="si">}</span><span class="s2"> - </span>
</span><span class='line'><span class="s2"> Adding them: </span><span class="si">#{</span><span class="n">accumulator</span><span class="si">}</span><span class="s2"> + </span><span class="si">#{</span><span class="n">element</span><span class="si">}</span><span class="s2"> = </span><span class="si">#{</span><span class="n">accumulator</span> <span class="o">+</span> <span class="n">element</span><span class="si">}</span><span class="s2">"</span>
</span><span class='line'>
</span><span class='line'> <span class="n">accumulator</span> <span class="o">+</span> <span class="n">element</span>
</span><span class='line'>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="c1">#=> accumulator: 1, element: 2 - Adding them: 1 + 2 = 3</span>
</span><span class='line'><span class="c1">#=> accumulator: 3, element: 3 - Adding them: 3 + 3 = 6</span>
</span><span class='line'><span class="c1">#=> accumulator: 6, element: 4 - Adding them: 6 + 4 = 10</span>
</span><span class='line'><span class="c1">#=> => 10 </span>
</span></code></pre></td></tr></table></div></figure>
<p>Here we can see we’re iterating over the array and adding the element to the accumulator each time through. If you look at the output from the puts you can see that the accumulator starts at 1, the first element in the array, and the element variable is given the 2nd element of the array. As it iterates through the array, the sum becomes the accumulator’s value and then is returned at the end of the iteration.</p>
<p>Here’s that same example but this time we’re multiplying the elements in the array.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="o">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="o">].</span><span class="n">inject</span> <span class="k">do</span> <span class="o">|</span><span class="n">accumulator</span><span class="p">,</span> <span class="n">element</span><span class="o">|</span>
</span><span class='line'>
</span><span class='line'> <span class="nb">puts</span> <span class="s2">"accumulator: </span><span class="si">#{</span><span class="n">accumulator</span><span class="si">}</span><span class="s2">, element: </span><span class="si">#{</span><span class="n">element</span><span class="si">}</span><span class="s2"> - </span>
</span><span class='line'><span class="s2"> Mulitplying them:</span><span class="si">#{</span><span class="n">accumulator</span><span class="si">}</span><span class="s2"> * </span><span class="si">#{</span><span class="n">element</span><span class="si">}</span><span class="s2"> = </span><span class="si">#{</span><span class="n">accumulator</span> <span class="o">*</span> <span class="n">element</span><span class="si">}</span><span class="s2">"</span>
</span><span class='line'>
</span><span class='line'> <span class="n">accumulator</span> <span class="o">*</span> <span class="n">element</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="c1">#=> accumulator: 1, element: 2 - Mulitplying them: 1 * 2 = 2</span>
</span><span class='line'><span class="c1">#=> accumulator: 2, element: 3 - Mulitplying them: 2 * 3 = 6</span>
</span><span class='line'><span class="c1">#=> accumulator: 6, element: 4 - Mulitplying them: 6 * 4 = 24</span>
</span><span class='line'><span class="c1">#=> => 24 </span>
</span></code></pre></td></tr></table></div></figure>
<h2>Giving the Accumulator a Starting Value</h2>
<p>In the last two examples we’re not giving the accumulator a starting value, however we have the option to do this by passing the value to the .inject method.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="o">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="o">].</span><span class="n">inject</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span> <span class="k">do</span> <span class="o">|</span><span class="n">accumulator</span><span class="p">,</span> <span class="n">element</span><span class="o">|</span>
</span><span class='line'>
</span><span class='line'> <span class="nb">puts</span> <span class="s2">"accumulator: </span><span class="si">#{</span><span class="n">accumulator</span><span class="si">}</span><span class="s2">, element: </span><span class="si">#{</span><span class="n">element</span><span class="si">}</span><span class="s2"> - </span>
</span><span class='line'><span class="s2"> Adding them: </span><span class="si">#{</span><span class="n">accumulator</span><span class="si">}</span><span class="s2"> + </span><span class="si">#{</span><span class="n">element</span><span class="si">}</span><span class="s2"> = </span><span class="si">#{</span><span class="n">accumulator</span> <span class="o">+</span> <span class="n">element</span><span class="si">}</span><span class="s2">"</span>
</span><span class='line'>
</span><span class='line'> <span class="n">accumulator</span> <span class="o">+</span> <span class="n">element</span>
</span><span class='line'>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="c1">#=> accumulator: 0, element: 1 - Adding them: 0 + 1 = 1</span>
</span><span class='line'><span class="c1">#=> accumulator: 1, element: 2 - Adding them: 1 + 2 = 3</span>
</span><span class='line'><span class="c1">#=> accumulator: 3, element: 3 - Adding them: 3 + 3 = 6</span>
</span><span class='line'><span class="c1">#=> accumulator: 6, element: 4 - Adding them: 6 + 4 = 10</span>
</span><span class='line'><span class="c1">#=> => 10 </span>
</span></code></pre></td></tr></table></div></figure>
<p>This time we’re summing the contents of the array, like in the first example, but we’re giving the inject method a value to set the accumulator to. Here we’ve set it to 0, but you can set it to anything you want. You can see from the output that the accumulator starts at 0 and the element variable is set to the first element in the array, 1.</p>
<p>But why do we want to set the accumulator to 0? This is just making us loop through one additional time?</p>
<p>For this summing example, this is true but if we we’re doing something to the element on each iteration, like say incrementing it by two, we need to give the accumulator variable a starting value. If we don’t then it uses the first element in the array, we can’t increment it, and thus don’t get the return value we want.</p>
<p>Here’s a look at this:</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
<span class='line-number'>31</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1">##### Giving the Accumulator a Starting Value #####</span>
</span><span class='line'>
</span><span class='line'><span class="o">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="o">].</span><span class="n">inject</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span> <span class="k">do</span> <span class="o">|</span><span class="n">accumulator</span><span class="p">,</span> <span class="n">element</span><span class="o">|</span>
</span><span class='line'>
</span><span class='line'> <span class="nb">puts</span> <span class="s2">"accumulator: </span><span class="si">#{</span><span class="n">accumulator</span><span class="si">}</span><span class="s2">, element + 2: </span><span class="si">#{</span><span class="n">element</span> <span class="o">+</span> <span class="mi">2</span><span class="si">}</span><span class="s2"> - Adding them: </span><span class="si">#{</span><span class="n">accumulator</span><span class="si">}</span><span class="s2"> + </span><span class="si">#{</span><span class="n">element</span> <span class="o">+</span> <span class="mi">2</span><span class="si">}</span><span class="s2"> = </span><span class="si">#{</span><span class="n">accumulator</span> <span class="o">+</span> <span class="p">(</span><span class="n">element</span> <span class="o">+</span><span class="mi">2</span><span class="p">)</span><span class="si">}</span><span class="s2">"</span>
</span><span class='line'>
</span><span class='line'> <span class="n">accumulator</span> <span class="o">+</span> <span class="p">(</span><span class="n">element</span> <span class="o">+</span> <span class="mi">2</span><span class="p">)</span>
</span><span class='line'>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="c1">#=> accumulator: 0, (element + 2): 3 - Adding them: 0 + 3 = 3</span>
</span><span class='line'><span class="c1">#=> accumulator: 3, (element + 2): 4 - Adding them: 3 + 4 = 7</span>
</span><span class='line'><span class="c1">#=> accumulator: 7, (element + 2): 5 - Adding them: 7 + 5 = 12</span>
</span><span class='line'><span class="c1">#=> accumulator: 12, (element + 2): 6 - Adding them: 12 + 6 = 18</span>
</span><span class='line'><span class="c1">#=> =>18</span>
</span><span class='line'>
</span><span class='line'>
</span><span class='line'><span class="c1">##### Omitting a Starting Value #####</span>
</span><span class='line'>
</span><span class='line'><span class="o">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="o">].</span><span class="n">inject</span> <span class="k">do</span> <span class="o">|</span><span class="n">accumulator</span><span class="p">,</span> <span class="n">element</span><span class="o">|</span>
</span><span class='line'>
</span><span class='line'> <span class="nb">puts</span> <span class="s2">"accumulator: </span><span class="si">#{</span><span class="n">accumulator</span><span class="si">}</span><span class="s2">, element + 2: </span><span class="si">#{</span><span class="n">element</span> <span class="o">+</span> <span class="mi">2</span><span class="si">}</span><span class="s2"> - Adding them: </span><span class="si">#{</span><span class="n">accumulator</span><span class="si">}</span><span class="s2"> + </span><span class="si">#{</span><span class="n">element</span> <span class="o">+</span> <span class="mi">2</span><span class="si">}</span><span class="s2"> = </span><span class="si">#{</span><span class="n">accumulator</span> <span class="o">+</span> <span class="p">(</span><span class="n">element</span> <span class="o">+</span><span class="mi">2</span><span class="p">)</span><span class="si">}</span><span class="s2">"</span>
</span><span class='line'>
</span><span class='line'> <span class="n">accumulator</span> <span class="o">+</span> <span class="p">(</span><span class="n">element</span> <span class="o">+</span> <span class="mi">2</span><span class="p">)</span>
</span><span class='line'>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="c1">#=> accumulator: 1, (element + 2): 4 - Adding them: 1 + 4 = 5</span>
</span><span class='line'><span class="c1">#=> accumulator: 5, (element + 2): 5 - Adding them: 5 + 5 = 10</span>
</span><span class='line'><span class="c1">#=> accumulator: 10, (element + 2): 6 - Adding them: 10 + 6 = 16</span>
</span><span class='line'><span class="c1">#=> =>16</span>
</span></code></pre></td></tr></table></div></figure>
<p>You can see that if we don’t set the accumulator to 0 we don’t increment the first element by 2 and thus get 16 when we really wanted 18. Because of this, it’s probably a good idea to get in the habit of setting the accumulator value no matter what.</p>
<h2>Altering Hashes</h2>
<p>Another use case for .inject (.reduce) is if you need to change the key or value in a hash.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">hash_of_state_capitals</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"CA"</span> <span class="o">=></span> <span class="s2">"Sacramento"</span><span class="p">,</span> <span class="s2">"NY"</span> <span class="o">=></span> <span class="s2">"Albany"</span><span class="p">,</span> <span class="s2">"ND"</span> <span class="o">=></span> <span class="s2">"Bismarck"</span><span class="p">}</span>
</span><span class='line'>
</span><span class='line'>
</span><span class='line'><span class="n">hash_of_state_capitals</span> <span class="o">=</span> <span class="n">hash_of_state_capitals</span><span class="o">.</span><span class="n">reduce</span><span class="p">({})</span> <span class="k">do</span> <span class="o">|</span><span class="n">new_hash</span><span class="p">,</span> <span class="p">(</span><span class="n">state</span><span class="p">,</span> <span class="n">capital</span><span class="p">)</span><span class="o">|</span>
</span><span class='line'>
</span><span class='line'> <span class="n">new_hash</span><span class="o">[</span><span class="n">state</span><span class="o">.</span><span class="n">to_sym</span><span class="o">]</span> <span class="o">=</span> <span class="n">capital</span>
</span><span class='line'>
</span><span class='line'> <span class="n">new_hash</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="c1">#=> {:CA=>"Sacramento", :NY=>"Albany", :ND=>"Bismarck"}</span>
</span></code></pre></td></tr></table></div></figure>
<p>In this example, we have a <code>hash_of_state_capitals</code> whose keys are strings, and we want to change them to symbols.</p>
<p>This time around, instead of setting the accumulator to a number we’re setting it to an empty hash ( <code>hash_of_state_capitals.reduce({})</code> ), which we’re calling “new_hash”. Then each time we loop through the hash_of_state_capitals we create the new_hash by setting the key to the <code>state.to_sym</code> and the value to capital. Then at the bottom we return the new hash, which is a must, and will throw an error if you don’t.</p>
<p>This method of altering a hash is a bit cleaner than using <code>.each</code> and can actually be done on a single line.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">hash_of_state_capitals</span> <span class="o">=</span> <span class="n">hash_of_state_capitals</span><span class="o">.</span><span class="n">reduce</span><span class="p">({})</span> <span class="p">{</span><span class="o">|</span><span class="n">new_hash</span><span class="p">,</span> <span class="p">(</span><span class="n">state</span><span class="p">,</span> <span class="n">capital</span><span class="p">)</span><span class="o">|</span> <span class="n">new_hash</span><span class="o">[</span><span class="n">state</span><span class="o">.</span><span class="n">to_sym</span><span class="o">]</span> <span class="o">=</span> <span class="n">capital</span><span class="p">;</span> <span class="n">new_hash</span><span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="c1">### OR ###</span>
</span><span class='line'>
</span><span class='line'><span class="n">hash_of_state_capitals</span> <span class="o">=</span> <span class="n">hash_of_state_capitals</span><span class="o">.</span><span class="n">reduce</span><span class="p">({})</span> <span class="p">{</span><span class="o">|</span><span class="n">new_hash</span><span class="p">,</span> <span class="p">(</span><span class="n">state</span><span class="p">,</span> <span class="n">capital</span><span class="p">)</span><span class="o">|</span> <span class="n">new_hash</span><span class="o">.</span><span class="n">merge</span><span class="p">(</span><span class="n">state</span><span class="o">.</span><span class="n">to_sym</span> <span class="o">=></span> <span class="n">capital</span><span class="p">)}</span>
</span></code></pre></td></tr></table></div></figure>
<h2>Building Arrays & Hashes</h2>
<p>You can use inject to build arrays and hashes similar to how you use other methods such as .map or .select. The advantage that inject has over these is you can use inject instead of chaining several methods together. This isn’t a big deal if you’re chaining just two methods together to achieve whatever you’re doing but your code could get messy if you go beyond that.</p>
<p>Here is a great example from <a href= "http://blog.jayfields.com/2008/03/ruby-inject.html" target="_blank">Jay Fields’ blog post</a> on Inject demonstrating how to use <code>.inject</code> to get all the integers of an array, that are even, as strings.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="c1">### Chaining Select & Collect ###</span>
</span><span class='line'><span class="o">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">6</span><span class="o">].</span><span class="n">select</span> <span class="p">{</span> <span class="o">|</span><span class="n">element</span><span class="o">|</span> <span class="n">element</span> <span class="o">%</span> <span class="mi">2</span> <span class="o">==</span> <span class="mi">0</span> <span class="p">}</span><span class="o">.</span><span class="n">collect</span> <span class="p">{</span> <span class="o">|</span><span class="n">element</span><span class="o">|</span> <span class="n">element</span><span class="o">.</span><span class="n">to_s</span> <span class="p">}</span>
</span><span class='line'>
</span><span class='line'><span class="c1"># => ["2", "4", "6"]</span>
</span><span class='line'>
</span><span class='line'>
</span><span class='line'><span class="c1">### Using Inject ###</span>
</span><span class='line'><span class="n">array</span> <span class="o">=</span> <span class="o">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">6</span><span class="o">].</span><span class="n">inject</span><span class="p">(</span><span class="o">[]</span><span class="p">)</span> <span class="k">do</span> <span class="o">|</span><span class="n">result</span><span class="p">,</span> <span class="n">element</span><span class="o">|</span>
</span><span class='line'> <span class="n">result</span> <span class="o"><<</span> <span class="n">element</span><span class="o">.</span><span class="n">to_s</span> <span class="k">if</span> <span class="n">element</span> <span class="o">%</span> <span class="mi">2</span> <span class="o">==</span> <span class="mi">0</span>
</span><span class='line'> <span class="n">result</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="c1"># => array = ["2", "4", "6"]</span>
</span></code></pre></td></tr></table></div></figure>
<p>An example of building a hash would be if you received an array with nested arrays, that you wanted to convert into a hash as key, value pairs.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">students</span> <span class="o">=</span> <span class="o">[[</span><span class="mo">01</span><span class="p">,</span> <span class="s2">"Jon"</span><span class="o">]</span><span class="p">,</span><span class="o">[</span><span class="mo">02</span><span class="p">,</span> <span class="s2">"Becca"</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mo">03</span><span class="p">,</span> <span class="s2">"Pete"</span><span class="o">]</span><span class="p">,</span> <span class="o">[</span><span class="mo">04</span><span class="p">,</span> <span class="s2">"Laura"</span><span class="o">]]</span>
</span><span class='line'>
</span><span class='line'><span class="n">students_hash</span> <span class="o">=</span> <span class="n">students</span><span class="o">.</span><span class="n">reduce</span><span class="p">({})</span> <span class="k">do</span> <span class="o">|</span><span class="n">students</span><span class="p">,</span> <span class="n">array</span><span class="o">|</span>
</span><span class='line'>
</span><span class='line'> <span class="n">students</span><span class="o">[</span><span class="n">array</span><span class="o">.</span><span class="n">first</span><span class="o">]</span> <span class="o">=</span> <span class="n">array</span><span class="o">.</span><span class="n">last</span>
</span><span class='line'>
</span><span class='line'> <span class="n">students</span>
</span><span class='line'><span class="k">end</span>
</span><span class='line'>
</span><span class='line'><span class="c1">#=> {1=>"Jon", 2=>"Becca", 3=>"Pete", 4=>"Laura"}</span>
</span></code></pre></td></tr></table></div></figure>
<p>
Here we have student’s IDs and names given to us as an array of arrays, but we want to convert this to a hash. The inject method takes care of this in a nice compact way, without having to create empty variables outside our loop.</p>
<p>Finally here is an example from the anagram_detector lab we did today.</p>
<figure class='code'><figcaption><span></span></figcaption><div class="highlight"><table><tr><td class="gutter"><pre class="line-numbers"><span class='line-number'>1</span>
<span class='line-number'>2</span>
<span class='line-number'>3</span>
<span class='line-number'>4</span>
<span class='line-number'>5</span>
<span class='line-number'>6</span>
<span class='line-number'>7</span>
<span class='line-number'>8</span>
<span class='line-number'>9</span>
<span class='line-number'>10</span>
<span class='line-number'>11</span>
<span class='line-number'>12</span>
<span class='line-number'>13</span>
<span class='line-number'>14</span>
<span class='line-number'>15</span>
<span class='line-number'>16</span>
<span class='line-number'>17</span>
<span class='line-number'>18</span>
<span class='line-number'>19</span>
<span class='line-number'>20</span>
<span class='line-number'>21</span>
<span class='line-number'>22</span>
<span class='line-number'>23</span>
<span class='line-number'>24</span>
<span class='line-number'>25</span>
<span class='line-number'>26</span>
<span class='line-number'>27</span>
<span class='line-number'>28</span>
<span class='line-number'>29</span>
<span class='line-number'>30</span>
<span class='line-number'>31</span>
<span class='line-number'>32</span>
<span class='line-number'>33</span>
<span class='line-number'>34</span>
<span class='line-number'>35</span>
<span class='line-number'>36</span>
</pre></td><td class='code'><pre><code class='ruby'><span class='line'><span class="n">anamgrams</span> <span class="o">=</span> <span class="sx">%w(gallery ballerina regally clergy largely leading)</span>
</span><span class='line'>
</span><span class='line'><span class="n">word</span> <span class="o">=</span> <span class="s1">'allergy'</span>
</span><span class='line'>
</span><span class='line'>
</span><span class='line'><span class="k">class</span> <span class="nc">Anagram</span>
</span><span class='line'> <span class="kp">attr_accessor</span> <span class="ss">:word</span>
</span><span class='line'>
</span><span class='line'> <span class="k">def</span> <span class="nf">initialize</span><span class="p">(</span><span class="n">word</span><span class="p">)</span>
</span><span class='line'> <span class="nb">self</span><span class="o">.</span><span class="n">word</span> <span class="o">=</span> <span class="n">word</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'>
</span><span class='line'> <span class="k">def</span> <span class="nf">word_sorter</span><span class="p">(</span><span class="n">word</span><span class="p">)</span>
</span><span class='line'> <span class="n">word</span><span class="o">.</span><span class="n">chars</span><span class="o">.</span><span class="n">sort</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="s2">""</span><span class="p">)</span>
</span><span class='line'> <span class="k">end</span>
</span><span class='line'>
</span><span class='line'>
</span><span class='line'> <span class="k">def</span> <span class="nf">match</span><span class="p">(</span><span class="n">array</span><span class="p">)</span>
</span><span class='line'> <span class="n">array</span><span class="o">.</span><span class="n">inject</span><span class="p">(</span><span class="o">[]</span><span class="p">)</span> <span class="k">do</span> <span class="o">|</span><span class="n">array</span><span class="p">,</span> <span class="n">element</span><span class="o">|</span>
</span><span class='line'> <span class="n">array</span> <span class="o"><<</span> <span class="n">element</span> <span class="k">if</span> <span class="n">word_sorter</span><span class="p">(</span><span class="n">element</span><span class="p">)</span> <span class="o">==</span> <span class="n">word_sorter</span><span class="p">(</span><span class="n">word</span><span class="p">)</span>
</span><span class='line'> <span class="n">array</span>
</span><span class='line'> <span class="k">end</span>