When I want to learn a new programming language or framework, I usually first try to find some examples to look at. Many times I have found it hard to find a single page with some good examples on how a language works. Not a tutorial, just examples. Here is a basic set of examples I would find nice to read if I wanted to learn about the Ruby on Rails web application development framework. Find more resources for learning the framework at the bottom of the post.
New Rails project
In the shell:
$ rails new example_project $ cd example_project
Models
In app/models/post.rb:
class Post < ActiveRecord::Base has_many :comments, :dependent => :destroy # post.comments with autodelete validates_presence_of :title, :content end
In app/models/comment.rb:
class Comment < ActiveRecord::Base belongs_to :post # comment.post validates_presence_of :text end
Controllers
In app/controllers/posts_controller.rb:
class PostsController < ApplicationController
def index
@posts = Post.all
end
def show
@post = Post.find(params[:id])
end
def new
@post = Post.new
end
def create
@post = Post.new(params[:post])
if @post.save
redirect_to @post, :notice => "The post was created successfully."
else
render :new
end
end
def edit
@post = Post.find(params[:id])
end
def update
@post = Post.find(params[:id])
if @post.update_attributes(params[:post])
redirect_to @post, :notice => "The post was updated successfully."
else
render :edit
end
end
def destroy
@post = Post.find(params[:id])
@post.destroy
redirect_to posts_path, :notice => "The post was deleted successfully."
end
end
Views
In app/views/posts/index.html.erb:
<h1>All posts</h1>
<ul>
<% @posts.each do |post| %>
<li><%= link_to post.title, post %></li>
<% end %>
</ul>
<p>
<%= link_to "New post", new_post_path %>
<%= link_to "Back to homepage", root_path %>
</p>
In app/views/posts/show.html.erb:
<h1><%= @post.title %></h1>
<p>
Created: <%= @post.created_at %>
</p>
<p>
<%= link_to "Delete post", @post, :method => :delete %>
</p>
<p>
<%= @post.content %>
</p>
<h2>Comments</h2>
<% @post.comments.each do |comment| %>
<p>
<%= comment.text %>
</p>
<% end %>
<%= link_to "Back to posts", posts_path %>
In app/views/posts/new.html.erb:
<h1>New post</h1>
<%= form_for @post do |f| %>
<p>
<%= f.label :title %><br />
<%= f.text_field :title %>
</p>
<p>
<%= f.label :content %><br />
<%= f.text_area :content %>
</p>
<p>
<%= f.submit "Create post" %>
</p>
<% end %>
View layouts
In app/views/layouts/application.html.erb:
<html>
<head>
<title>Rails example</title>
</head>
<body>
<% if flash[:notice] %>
<p><%= flash[:notice] %></p>
<% end %>
<%= yield %>
</body>
</html>
View partials
In app/views/shared/_example_partial.html.erb:
<p> Content of example variable: <%= example_variable %> </p>
In another view:
<%= render "shared/example_partial", :example_variable => "Example content" %>
Rendering other formats
In app/controllers/posts_controller.rb:
class PostsController < ApplicationController
def index
@posts = Post.all
respond_to do |format|
format.html # index.html.erb
format.json { render :json => @posts }
end
end
end
In the browser:
http://localhost:3000/posts.json
Database migrations
In the shell:
$ rails generate model post title:string content:text
In db/migrate/20121228215855_create_posts.rb:
class CreatePosts < ActiveRecord::Migration
def change
create_table :posts do |t|
t.string :title
t.text :content
t.timestamps
end
end
end
In the shell:
$ rails generate model comment post_id:integer text:text
In db/migrate/20121228220327_create_comments.rb:
class CreateComments < ActiveRecord::Migration
def change
create_table :comments do |t|
t.integer :post_id
t.text :text
t.timestamps
end
add_index :comments, :post_id
end
end
Then, in the shell:
$ rake db:migrate
Routing
In config/routes.rb:
ExampleProject::Application.routes.draw do
resources :posts do # /posts, /posts/123, etc. => PostsController
resources :comments # /posts/123/comments, /posts/123/comments/345, etc. => CommentsController
end
match "contact" => "home#contact" # /contact => HomeController#contact
root :to => "home#index" # / => HomeController#index
end
Plugins
In Gemfile:
# To use jQuery gem 'jquery-rails' # To use Jbuilder templates for JSON gem 'jbuilder' # Deploy with Capistrano gem 'capistrano'
In the shell:
$ bundle install
Rails development server
In the shell:
$ rails server
To see posts:
http://localhost:3000/posts
To see a single post:
http://localhost:3000/posts/123
To edit a post:
http://localhost:3000/posts/123/edit
See also
- What is Ruby on Rails (an introduction) – a general introduction to Ruby on Rails
- Ruby on Rails official site – the official site with info on Ruby on Rails
- Ruby on Rails official guides – introductory guides to get started
- RailsCasts – a lot of useful screencasts about Ruby on Rails
- TryRuby – an interactive shell where you can try the Ruby language
- Ruby on Wikipedia – Wikipedia article on the Ruby language