Question

I’m trying to set up a javascript front in that is consuming JSON from a Rails backend.

The only problem is, when I have nested models in Rails, I’m not sure if the JSON being returned is in the correct format.

I have a Post model and a Comment model. A Post has many Comments. Each model has a ‘title’ and ‘content’ field.

Here’s where my problem is so far…

1) When I visit the url: http://localhost:3000/posts.json I get the expected output:

> [{"content":"My first
> post","created_at":"2012-02-07T18:56:16Z","id":1,"title":"Hello","updated_at":"2012-02-07T18:56:16Z"},{"content":"More
> crap","created_at":"2012-02-07T21:30:51Z","id":2,"title":"My 2nd
> Post","updated_at":"2012-02-07T21:30:51Z"}]

2) If I put in this url: http://localhost:3000/posts/1/comments/4.json I also get the expected:

> {"content":"that's
> nice","created_at":"2012-02-07T20:57:16Z","id":4,"post_id":1,"title":"cool","updated_at":"2012-02-07T20:57:16Z"}

3) But… if I put in a url like this: http://localhost:3000/posts/1/comments.json

it returns null.

I don’t have access to the JSON version of the list of Comments associated with the Post.

Using the standard Rails views, I can do full CRUD with the nesting no problem, but do I need to do something different from the way Rails normally passes the JSON back in order to consume it on the client side?

---

EDIT

I’m assuming you may need to see the controller code for the comments controller. Here it is:

class CommentsController < ApplicationController

  before_filter :get_post  

  respond_to :html, :xml, :json

  def index
    @comments = @post.comments.all    
    respond_with (@comment)    
  end

  def show
    @comment = @post.comments.find(params[:id])

    respond_with(@comment)

  end

  def new
    @comment = @post.comments.build

    respond_with(@comment)
  end

  def edit
    @comment = @post.comments.find(params[:id])
  end

  def create
    @comment = @post.comments.build(params[:comment])

    respond_to do |format|
      if @comment.save
        format.html { redirect_to([@post, @comment], :notice => 'Comment was successfully created.') }
        format.xml  { render :xml => @comment, :status => :created, :location => @comment }
        format.json  { render :json => @comment, :status => :created, :location => @comment }
      else
        format.html { render :action => "new" }
        format.xml  { render :xml => @comment.errors, :status => :unprocessable_entity }
        format.json  { render :json => @comment.errors, :status => :unprocessable_entity }
      end
    end
  end

 def update
    @comment = @post.comments.find(params[:id])

    respond_to do |format|
      if @comment.update_attributes(params[:comment])
        format.html { redirect_to(@comment, :notice => 'Comment was successfully updated.') }
        format.xml  { head :ok }
        format.json  { head :ok }
      else
        format.html { render :action => "edit" }
        format.xml  { render :xml => @comment.errors, :status => :unprocessable_entity }
        format.json  { render :json => @comment.errors, :status => :unprocessable_entity }
      end
    end
  end

  def destroy
    @comment = @post.comments.find(params[:id])
    @comment.destroy

    respond_to do |format|
      format.html { redirect_to(post_comments_url) }
      format.xml  { head :ok }
      format.json  { head :ok }
    end
  end  

  protected  

  def get_post
    @post = Post.find_by_id(params[:post_id])
    redirect_to root_path unless @post
  end

end

Answer 1

def index
    @comments = @post.comments.all    
    respond_with (@comment)    
end

You didn’t assign to @comment.