Rajeev Kannav Sharma

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ReactJS - To start guide for Rails developers. Part - 1

30 May 2015

Introduction to React.js

React is a JavaScript library for creating user interfaces by Facebook and Instagram. Many people choose to think of React as the V in MVC. We built React to solve one problem: building large applications with data that changes over time. To do this, React uses two main ideas. For more details visit

A mock expense tracking app

For this guide, we are building a small application from scratch to keep track of our expenses; each record will consist of a date, a title and an amount. A record will be treated as Credit if its amount is greater than zero, otherwise it will be treated as Debit. Here is a mockup of the project:


Summarizing, the application will behave as follows:

  • When the user creates a new record through the horizontal form, it will be appended to the records table
  • The user will be able to inline-edit any existing record
  • Clicking on any Delete button will remove the associated record from the table
  • Adding, editing or removing an existing record will update the amount boxes at the top of the page

Let’s Start

# First things first we need to started our brand new Rails project
rails new reactExample

# Add react-rails to your Gemfile.
gem 'react-rails', '~> 1.0'

react-rails comes with an installation script, which will create a components.js file and a components directory under app/assets/javascripts where our React components will live.

  rails g react:install

If you take a look at your application.js file after running the installer, you will notice three new lines:

//= require react
//= require react_ujs
//= require components
rails g resource Record title date:date amount:float # Creating the Resource

rake db:create db:migrate
Record.create title: 'Record 1', date: Date.today, amount: 500
Record.create title: 'Record 2', date: Date.today, amount: -100

rake db:seed

Nesting Components: Listing Records

class RecordsController < ApplicationController
  def index
    @records = Record.all
<%= react_component 'Records', { data: @records } %>
    @Records = React.createClass
      getInitialState: ->
        records: @props.data
      getDefaultProps: ->
        records: []
      render: ->
          className: 'records'
            className: 'title'
            className: 'table table-bordered'
            React.DOM.thead null,
              React.DOM.tr null,
                React.DOM.th null, 'Date'
                React.DOM.th null, 'Title'
                React.DOM.th null, 'Amount'
            React.DOM.tbody null,
              for record in @state.records
                React.createElement Record, key: record.id, record: record
     @amountFormat = (amount) ->
       '$ ' + Number(amount).toLocaleString()
     @Record = React.createClass
       render: ->
         React.DOM.tr null,
           React.DOM.td null, @props.record.date
           React.DOM.td null, @props.record.title
           React.DOM.td null, amountFormat(@props.record.amount)

Current State

You can take a look at the resulting code of this section here, And Please wait for Part-2.

And if you get stuck… Ask Here

email me rajeevsharma86@gmail.com

Tweet to me at @rajeevkannav.