Source Code for Workshop on using Ruby on Rails to make a Trip Mapping Service
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Trip Mapper Demo

This Repository is part of a workshop given at HackDuke 2016 on how to make Web Applications in Ruby on Rails by Geng Sng. The talk will be held at Duke University on 19 Nov 2016, 6pm at Hudson Hall 208, and is meant for beginners.

You can find the slides used for the workshop here:

Bring yourself and a keen sense of learning! (and your laptop!)

Instructions Before We Begin

In order to make it easier for all attendees, please do the following before attending the workshop:

  • Register for a Github Account

  • Attend Dev & Jiawei's workshop on Intro to Git (Hudson Hall 208, 3-4pm on 19 Nov)

  • Install Ruby on Rails

If you already have ruby / rails installed, please ensure that you have the following versions:


Ruby '~> 2.3.0'

Rails '~> 5.0.0'

Trip Mapper

In this workshop, we will be creating a simple trip mapper using Ruby on Rails. We will be using the Google Maps API and several gems to get our web app up and running quickly.


We will be making our app from scratch, so once you've installed Rails and got a github account, let's begin!

We begin by initializing our new rails app. So go ahead type rails new app_name -d postgresql in your directory of choice, to create a new rails app. You will see that many files are being generated for you, that's Rails doing the heavy-lifting for you right there. We add -d postgresql to configure our app to use the PostgreSQL database instead of the default sqlite3.

Once you've done that, we should move into our new rails app by running the following command in terminal: cd app_name

Then we want to link our link our local repo to our github repo, by doing the following:

  • login to Github and create a new repo
  • copy the repo URL
  • git remote add origin GIT_URL
  • git push -u origin master

Some of you familiar with git may notice that we did not run git init to initialize git in our app. That's because rails already initializes git in any new Rails app by default.

Now let's run rails s to check if we got everything right so far.

Go to http://localhost:3000 to see your app running on localhost. The default localhost for Rails is 3000 but you can set it to whatever you want. For this workshop we'll be using localhost:3000 .

Congrats! You've made your first Rails application!

List of Commands so far:

rails new app_name -d postgresql
cd app_name
git remote add origin git_url
git push -u origin master
rails s


Next, open up your app in your text editor of choice by running this command: [text_editor_name] .

You should see a huge line of folders. Search for a file called Gemfile and double-click on it.

Paste the following into your Gemfile:

# database: postgresql
gem 'pg'
# heroku deployment
gem 'rails_12factor', group: :production
# user auth
gem 'devise'
# jQuery
gem 'jquery-rails'
# relational mapping
gem "rails-erd"
# geocoding to get lat and long values
gem 'geocoder'
# bootstrap generator
gem 'bootstrap-generators'
# mapping
gem 'gmaps4rails', '~> 2.0.3'
# to add 'content_tag_for' method which was removed from Rails 5.0
gem 'record_tag_helper', '~> 1.0'
# google's MarkerClusterer.js
gem 'markerclustererplus-rails'

Ruby Gems are cool and small libraries that developers have made to make running common features easier. By installing a ruby gem, we gain access to the library that was made and the gem becomes a part of the dependencies of your application. Gems are one of the biggest reasons why people use Rails, because it makes everything so easy and fast!

Now let's run bundle install to install our dependencies

Run the following in your Terminal:

git add .
git commit -m '[any message here]'
bundle install

It's good practice to stage and commit every time you make a change to your code. After we've installed our ruby gems, we should git add . and git commit -m '[commit message]' as above to ensure that we track all the versions of our code.

User Authentication with Devise

We've used a nifty gem called Devise to handle user authentication in our application. You can find find the documentation for Devise here.

According to this documentation, all we need to do is run these commands to get up and running:

rails generate devise:install

Now open up your app in your text editor again and look for:


Add the following config inside:

config.action_mailer.default_url_options = { host: 'localhost', port: 3000 }

Then run this command: rails generate devise User

This will create a User model and the corresponding files using the Rails framework that gives us options which include user authentication and view pages for login and sign up.

Once we've generated a new User, we want to migrate our database to ensure that our database is synced with our Rails app.

rails db:migrate

BootStrap Generator

Now that we have the basics of our web app up, let's generate some bootstrap templates to make our app look better. BootStrap is a common framework used by web developers to make styling websites easier.

We will be using the gem bootstrap-generators to generate a template for each model that we subsequently create.

Run the following command in terminal:

rails g bootstrap:install

Now when we generate new models, a corresponding template will be generated for that model.

Creating Trips

For this app, we will only be creating one model: trips. If you wanted to expand this app, you could easily create other models and assign relationships to them so that they are mapped in your database. We will not be going into how to do this in this demo, but if you have questions please feel free to get in touch with me.

To create a trip, run this command:

rails g scaffold Trip latitude:float longitude:float name:string address:string title:string

You should see Rails generating some files for you. g is short for generate. You can use these 2 terms interchangeably in Rails.

Imagine you are creating an excel sheet and you want to specify properties that belong to a trip. We are making a column for each of the properties latitude longitude and so on, and specifying the type of data that goes into that column via :float or :string. That's how the Trip that we just created is going to look like in our database.

In app/models/trip.rb, add the following:

geocoded_by :address
after_validation :geocode

This tells our trip model to geocode the address provided to it when we create a new trip.

In app/controllers/trips_controller.rb add the following:

def index
  @trips = Trip.all
  @hash = Gmaps4rails.build_markers(@trips) do |trip, marker| trip.latitude
    marker.lng trip.longitude

This creates markers based on the geocoded lat and long values in the map

Next, to migrate our database based on our newly generated Trip, run:

rails db:migrate

Now run rails s and take a look at your localhost. You should see that there's some default styling going on here, even though we did not do any styling on our own. That's the gem bootstrap-generators in action right there!

Adding Sign In / Sign Out Buttons

Before we move on, let's add some sign in and out buttons to our app:

In app/views/layouts/application.html.erb add this chunk of code:

<div id="navbar" class="collapse navbar-collapse">
  <ul class="nav navbar-nav">
    <li class="active"><a href="#">Home</a></li>
    <li><a href="#about">About</a></li>
    <li><a href="#contact">Contact</a></li>
   <!-- Add this part -->
  <ul class='nav navbar-nav navbar-right'>
    <% if user_signed_in? %>

    <li><%= link_to 'Sign Out', destroy_user_session_path, method: :delete%></li>
    <% else %>
    <li><%= link_to 'Sign In', new_user_session_path %></li>
    <% end %>
  <!-- end -->

You should see a div tag with the id id="navbar". Add in the part that is encapsulated by the comments above. We are toggling between Sign In and Sign Out buttons when the user is signed in. If you notice the <% %> those are scriptlets in the Embedded Ruby templating language. You should notice that our html file has a html.erb extension. Erb basically allows us to enter ruby scripts into html, which is more convenient since you can access the functions and instance variables created in your controller here. the user_signed_in? function is an example of a function that's created by the Devise gem that we are accessing. You can't find it in your code because Devise generates a hidden file that stores all these methods. If you want to find out all the methods Devise creates, refer to its documentation.

Then we need to add the following in assets/javascripts/application.js:

//= require jquery
//= require jquery_ujs

Now refresh your rails app and see the changes!

You can now sign in, sign out, and sign up. The pages are all created for you using Devise. Isn't that handy?

Updating Routes

After creating a new model in Rails, you should always updated your routes based on how you want your app to work. Routes handle the HTTP requests and responses between your frontend and the backend. By default, Rails will generate routes for you when you create a new model.

What we want to do now is to set a root page for our app, so localhost will always point to it. In app/config/routes.rb add the following:

root 'trips#index'

This assigns a root page for your app. In this case, we assign the index.html.erb of our Trips to the root, so localhost:3000 and eventually your website, will show the index.html.erb page for Trips by default.

Getting ready to create Maps

Now that we have the skeleton of the app up, we want to enable it to geocode any address that you enter into the app, and mark it on a map, so that you can plan trips with your friends.

In order to create a map and create markers on it, we'll be using the following:

  • minified underscore.js
  • gem 'gmaps4rails'
  • google maps API + key
  • gem 'markerclustererplus'

Let's grab the underscore.js source code and paste it into vendor/assets/javascripts as underscore.js

Then we need to add the following in assets/javascripts/application.js:

//= require underscore
//= require gmaps/google
//= require markerclusterer

We do this so that Rails knows that we are using these 2 libraries in our application when it's loading javascript. To see more about gmaps4rails, see here.

Now we want to generate a copy of the js file that gmpas4rails requires. This step is provided in the documentation for gmaps4rails.

rails g gmaps4rails:copy_js

Now let's set a div tag in index.html.erb for our map:

<div style='height:400px; position: relative; padding-bottom: 75%; height: 0; overflow:hidden'>
  <div id="map" style='width: 100%; height: 100%; position: absolute; top: 0; left: 0;'></div>

To catch errors, let's include a div at the top of the page:

<div id="warnings_panel"></div>

Now we want to paste some in-line javascript into our index page to render the map.

In views/layouts/trips/index.html.erb paste:

<script type="text/javascript">
function initMap() {
  handler ='Google');
  handler.buildMap({ provider: {}, internal: {id: 'map'}}, function(){
    markers = handler.addMarkers(<%=raw @hash.to_json %>);

  var directionsDisplay = new google.maps.DirectionsRenderer({ polylineOptions:{strokeColor:"#4a4aff",strokeWeight:5}, suppressMarkers:false });
  var directionsService = new google.maps.DirectionsService();
  var map = new google.maps.Map(document.getElementById('map'));

function calcRoute(){
  <% @waypts = []; %>
  <% @trips.each_with_index do |t, index| %>
      <% if index == 0
       elsif index == (@trips.size - 1)
         @waypts.push({:location => t.address, :stopover => true})
       end %>
  <% end %>

  var directionsRequest = {
    origin: <%=raw @hash.first.to_json %>,
    destination: <%=raw @hash.last.to_json %>,
    waypoints: <%= raw @waypts.to_json %>,
    optimizeWaypoints: true,
    travelMode: google.maps.DirectionsTravelMode.DRIVING,
    unitSystem: google.maps.UnitSystem.METRIC
  directionsService.route(directionsRequest, function(response, status) {
    if (status == 'OK') {
      var warnings = document.getElementById("warnings_panel")
      warnings.innerHTML = "" + response.routes[0].warnings + ""
    } else {
      window.alert('Directions request failed due to ' + status);


<script async defer src=""></script>

You should get your own API key.


Congratulations! You've got a working rails trip mapper application!

Remember how the Rails framework works:

  • MVC
  • generating models, views, controllers, etc
  • See it's wonderful documentation
  • Hit me up if you need help on any web application you're building

Now go off and hack!