Ruby on Rails tutorial describing how to link an amCharts JavaScript chart to the data in your database
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README.md

#Ruby on Rails Tutorial - How to create an amCharts graph that pulls data from a database to populate the graph


amCharts is a set of JavaScript/HTML5 charts. This tutorial covers how to pull data from a database to populate a graph or chart.

A big thanks to @chiragsinghal for helping me get this working. Any mistakes in this tutorial are purely my own.

For this tutorial I am using Rails 3.2.3 and Ruby 1.9.3p125 (2012-02-16 revision 34643) [x86_64-darwin10.8.0].

#amCharts Tutorial


###Section 1 - Create a new project

  1. Create a new repository on GitHub named 'amcharts_example'

  2. Create a new rails project

    $ rails new amcharts_example $ cd amcharts_example

  3. Open the project in your favorite text editor (Example: I am using Sublime Text 2)

    $ subl .

  4. Update the Gemfile

    source 'https://rubygems.org'

    gem 'rails', '3.2.3'

    group :development, :test do gem 'sqlite3', '1.3.5' gem 'rspec-rails', '2.9.0' end

    Gems used only for assets and not required

    in production environments by default.

    group :assets do gem 'sass-rails', '3.2.4' gem 'coffee-rails', '3.2.2' gem 'uglifier', '1.2.3' end

    gem 'jquery-rails', '2.0.0'

    group :test do gem 'capybara', '1.1.2' end

    group :production do gem 'pg', '0.12.2' end

  5. Install and include the new gems

    $ bundle install

  6. Initialize the Git repository and push to GitHub

    $ git init $ git add . $ git commit -m "Initial commit" $ git remote add origin git@github.com:/amcharts_example.git $ git push -u origin master

  7. (Optional) Deploy the app to Heroku. (Assuming you have already created a Heroku account. If not, check out this tutorial)

    $ heroku create --stack cedar $ git push heroku master

###Section 2 - Create a static page to display the graph

  1. Generate a StaticPages controller

    $ rails generate controller StaticPages mygraph

  2. Download the latest version of the amCharts JavaScript Charts release from their website

  3. From the download, copy the file 'amcharts.js' and paste it in the project file directory in the app/assets/javascripts folder.

  4. Add a graph to the view of the new static page mygraph.html.erb

    My amCharts Graph

    This is my amCharts graph

    <script type="text/javascript"> var chart; var chartData = [{ country: "USA", visits: 4025 }, { country: "China", visits: 1882 }, { country: "Japan", visits: 1809 }, { country: "Germany", visits: 1322 }, { country: "UK", visits: 1122 }, { country: "France", visits: 1114 }, { country: "India", visits: 984 }, { country: "Spain", visits: 711 }, { country: "Netherlands", visits: 665 }, { country: "Russia", visits: 580 }, { country: "South Korea", visits: 443 }, { country: "Canada", visits: 441 }, { country: "Brazil", visits: 395 }, { country: "Italy", visits: 386 }, { country: "Australia", visits: 384 }, { country: "Taiwan", visits: 338 }, { country: "Poland", visits: 328 }]; AmCharts.ready(function () { // SERIAL CHART chart = new AmCharts.AmSerialChart(); chart.dataProvider = chartData; chart.categoryField = "country"; chart.startDuration = 1; // AXES // category var categoryAxis = chart.categoryAxis; categoryAxis.labelRotation = 90; categoryAxis.gridPosition = "start"; // GRAPH var graph = new AmCharts.AmGraph(); graph.valueField = "visits"; graph.balloonText = "[[category]]: [[value]]"; graph.type = "column"; graph.lineAlpha = 0; graph.fillAlphas = 0.8; chart.addGraph(graph); chart.write("chartdiv"); }); </script>
  5. Commit the changes

    $ git add . $ git commit -am "Added a StaticPages Controller and amcharts.js" $ git push $ git push heroku

  6. Test it on the local server (start the server)

    $ rails s

And visit: http://localhost:3000/static_pages/mygraph

  1. Deploy and test it on Heroku

    $ heroku open

Now navigate to http://[yourappname].herokuapp.com/static_pages/mygraph

You can visit the example for this tutorial here: http://amcharts-example.herokuapp.com/static_pages/mygraph

###Section 3 - Add a model

We will add a 'Country' model (and the corresponding 'Countries' controller). In this database we will store the data for each country and the number of visits.

  1. Add a 'Countries' controller

    $ rails generate controller Countries new

  2. Add a 'Country' model

    $ rails generate model Country country:string visits:integer

(Note that, in contrast to the plural convention for controller names, model names are singular.)

  1. Migrate up the database

    $ bundle exec rake db:migrate

  2. Update the routes.rb file

    resources :countries, only: [:new, :create]

    match '/countries/new', to: 'countries#new' match '/static_pages/mygraph', to: 'static_pages#mygraph'

  3. Update the countries controller

    class CountriesController < ApplicationController def new @countries = Country.new

     respond_to do |format|
      format.html  # new.html.erb
      format.json  { render :json => @countries }
     end
    

    end

    def create @countries = Country.new(params[:country]) if @countries.save redirect_to '/static_pages/mygraph' else redirect_to '/countries/new' end end end

  4. Update the countries/new.html.erb view

    New Country

    Enter some new data

    <%= form_for(@countries) do |f| %>

    <%= f.label :country %> <%= f.text_field :country %>

    <%= f.label :visits %> <%= f.text_field :visits %>

    <%= f.submit "Save" %>

    <% end %>

*NB: We have not added any validations to our model (and we also do not have any validations on the client side, just a text field). When you create your own model, you will want to make sure that you are vaildating the data that is going into your model.

  1. Make the graph dynamic (pulling the data from the database). Update 'var chartData' in the static_pages/mygraph view

    var chartData = <%= raw @countries.to_json.gsub(/"created_at"/, "created_at").gsub(/"id"/, "id").gsub(/"country"/, "country").gsub(/"visits"/, "visits").gsub(/"updated_at"/, "updated_at") %>;

*NB: On first glance, it might seem like amCharts supports JSON data. However, it is actually not valid JSON and we need to adjust the JSON data accordingly.

21a) To refactor the above, we can pull the logic out of the view and create a helper method. Thanks to @chiragsinghal for pointing this out. This will also help keep your code DRY if you have multiple graphs.

Open static_pages_helper.rb and edit the code as follows:

module StaticPagesHelper
  def convert_to_amcharts_json(data_array)
    data_array.to_json.gsub(/\"text\"/, "text").html_safe
  end
end

Then you can change the 'var chartData' to the following:

var chartData = <%= convert_to_amcharts_json(@countries) %>;    
  1. Update the StaticPages controller

    class StaticPagesController < ApplicationController def mygraph @countries = Country.find(:all) end end

  2. Commit the changes and test on the local server

    $ git add . $ git commit -am "completed dynamic graph" $ git push $ rails s

And visit: http://localhost:3000/countries/new and enter in some data:

Example; Country: Japan Visits: 300

You should now see a bar graph with one bar! Your graph is now dynamic and tied to your model.

  1. Push to Heroku and test

    $ git push heroku $ heroku run rake db:migrate $ heroku open

Now navigate to http://[yourappname].herokuapp.com/countries/new

You can visit the example for this tutorial here: http://amcharts-example.herokuapp.com/countries/new and enter in some data.