Ruby on Rails中的模型之间的关系

Question

I'm new to Rails and working on my first app. What I want to achieve is an facebook like groups with their own walls and comments. Sounds pretty easy :)

I currently have 3 models: Group, Post and Comment. Here's the code:

class Group < ActiveRecord::Base
  attr_accessible :affiliation, :group_name, :group_type, :string

  validates :group_name, :presence => true
  has_many :posts, :dependent => :destroy, :foreign_key => "id"
end

class Post < ActiveRecord::Base
  attr_accessible :body, :posted_by, :posted_by_uid

  validates :body, :presence => true
  belongs_to :group
  has_many :comments, :dependent => :destroy
end

class Comment < ActiveRecord::Base
  attr_accessible :body, :commenter

  belongs_to :post
end

I managed to properly relate Comments to Posts. Its views are OK. But when I tried to relate Posts to Groups for some reason Posts (with corresponding Comments) are not Showing up.

Here's the snippet from Show view:

<b>Posts</b>
<%= render @group.posts %>

Posts partial (_post.html.erb in Posts forlder)

<h1>New post</h1>
<%= render 'form' %>

<p>
  <b> Content </b>
  <%= @post.body %>
</p>

<h2>Comments</h2>
<%= render @post.comments %>  

<h2>Add a comment:</h2>
<%=  render "comments/form" %>
<br />

PS I have no idea why I added foreign key, but without it i would get error (column group.posts.id doesn't exist), I just somehow figured it out comparing with other questions on stackoverflow that foreign key might choose the problem. It did, but it's not showing Posts.

Answer 1

Make sure that the posts table has a column group_id , then you should be able to remove the foreign key part.

If @group doesn't have any posts then it won't render the partial. Calling @group.posts will return an array, which is then iterated over and render is called for each object. If there are no posts then an empty array is returned, and the partial won't be rendered.

Change it to the following:

groups#show view:

<h1>New post</h1>
<%= render 'posts/form' %>

<b>Posts</b>
<%= render @group.posts %>

_post.html.erb partial:

<p>
  <b> Content </b>
  <%= @post.body %>
</p>

<h2>Comments</h2>
<%= render @post.comments %>  

<h2>Add a comment:</h2>
<%= render "comments/form" %>
<br />