Rails Study(III)Creating a sample

Rails Study(III)Creating a sample

7. Adding a Second Model
7.1 Generating a Model
>rails generate model Comment commenter:string body:text post:references
class Comment < ActiveRecord::Base
  belongs_to :post
end

The model belongs_to
migrate database to mysql
>rake db:migrate

7.2. Associating Models
edit post.rb and add the other side of the association:
  has_many :comments
If you have an instance variable @post containing a post, you can retrieve all the comments belonging to that post
as the array @post.comments

7.3 Adding a Route for Comments
>vi routes.rb
Railsexample::Application.routes.draw do
  root :to => "home#index"
  resources :posts do
    resources :comments
  end
end  

7.4 Generating a Controller
>rails generate controller Comments

Link the comments pages to posts pages.
<h2>Add a comment:</h2>
<%= form_for([@post, @post.comments.build]) do |f| %> 
<div class="field">    
<%= f.label :commenter %><br />    
<%= f.text_field :commenter %> 
</div>  
<div class="field">    
<%= f.label :body %><br />    
<%= f.text_area :body %> 
</div>  
<div class="actions">    
<%= f.submit %> 
</div>
<% end %>

Link the controller
  def create    
    @post = Post.find(params[:post_id])    
    @comment = @post.comments.create(params[:comment])    
    redirect_to post_path(@post)  
  end

show comments on the post page
<h2>Comments</h2>
<% @post.comments.each do |comment| %> 
<p>    
<b>Commenter:</b>    
<%= comment.commenter %> 
</p>    
<p>    
<b>Comment:</b>    
<%= comment.body %> 
</p>
<% end %>

It is done. Go to the URL http://localhost:3000/posts/2 to add comments.

8. Refactoring
8.1 Rendering Partial Collections
create the file app/views/comments/_comment.html.erb
<p>  
<b>Commenter:</b>  
<%= comment.commenter %>
</p>  
<p>  
<b>Comment:</b>  
<%= comment.body %>
</p>

change the file show.html.erb to >
<h2>Comments</h2>
<%= render :partial => "comments/comment",           
           :collection => @post.comments %>

8.2. Rendering a Partial Form
create a file app/views/comments/_form.html.erb
<%= form_for([@post, @post.comments.build]) do |f| %> 
<div class="field">    
<%= f.label :commenter %><br />    
<%= f.text_field :commenter %> 
</div>  
<div class="field">    
<%= f.label :body %><br />    
<%= f.text_area :body %> 
</div>  
<div class="actions">    
<%= f.submit %> 
</div>
<% end %>

edit the page show.html.erb>
<h2>Add a comment:</h2>
<%= render "comments/form" %>

9. Deleting Comments
in file /app/views/comments/_comment.html.erb
<p>  
<%= link_to 'Destroy Comment', [comment.post, comment],               
:confirm => 'Are you sure?',               
:method => :delete %>
</p>

add delete method in controller
  def destroy    
    @post = Post.find(params[:post_id])    
    @comment = @post.comments.find(params[:id])    
    @comment.destroy    
    redirect_to post_path(@post)  
  end

9.1 Deleting Associated Objects
change in app/models/post.rb
  has_many :comments, :dependent => :destroy

10. Security
Rails provides a very simple HTTP authentication system that will work nicely in this situation.
edit our controller app/controllers/application_controller.rb
  protect_from_forgery    
 
  private    
 
  def authenticate      
    authenticate_or_request_with_http_basic do |user_name, password|      
      user_name == 'admin' && password == 'password'  
    end
  end

I put put this method inside of ApplicationController so that it is available to all of our controllers.
In post controller
  before_filter :authenticate, :except => [:index, :show]

In comments controller
  before_filter :authenticate,nly => :destroy

11. Building a Multi-Model Form
Create a new model to hold the tags
>rails generate model tag name:string post:references
>rake db:migrate

edit the post.rb file to create the other side of the association. And to tell rails that you intend to edit tags via posts.
accepts_nested_attributes_for
has_many :tags
  accepts_nested_attributes_for :tags, :allow_destroy => :true,    
                                :reject_if => proc { |attrs| attrs.all? { |k, v| v.blank? } }

The :allow_destroy option on the nested attribute declaration tells Rails to display a "remove" checkbox on the view that you'll
build shortly.
The :reject_if option prvents saving new tags that do not have any attributes filled in.

modify views/posts/_form.html.erb to render a partial to make a tag:
<% @post.tags.build %>
<%= form_for(@post) do |post_form| %>
...snip...
<%= render :partial => 'tags/form',             
       :locals => {:form => post_form} %>
  <div class="field">
    <%= post_form.label :content %><br />
    <%= post_form.text_area :content %>
  </div>

create folder app/views/tags and a new file _form.html.erb
<%= form.fields_for :tags do |tag_form| %> 
<div class="field">    
<%= tag_form.label :name, 'Tag:' %>   
<%= tag_form.text_field :name %> 
</div>  
<% unless tag_form.object.nil? || tag_form.object.new_record? %>   
<div class="field">      
<%= tag_form.label :_destroy, 'Remove:' %>     
<%= tag_form.check_box :_destroy %>   
</div>  
<% end %>
<% end %>

edit app/views/posts/show.html.erb template to show our tags.
<p>  
<b>Tags:</b>  
<%= @post.tags.map { |t| t.name }.join(", ") %>
</p>

12 View Helper
Put all the reusable code for views.
edit app/helpers/posts_helper.rb
module PostsHelper  
  def join_tags(post)    
    post.tags.map { |t| t.name }.join(", ")  
  end
end

change show.html.erb from
<p>  
<b>Tags:</b>  
<%= @post.tags.map { |t| t.name }.join(", ") %>
</p>

to

<p>  
<b>Tags:</b>  
<%= join_tags(@post) %>
</p>

references:
http://guides.rubyonrails.org/getting_started.html