Question

Ok ill be honest, i haven’t spent much time looking for a solution yet seeing as how my son is keeping my attention running around. Either way I would like to ask a question for something that seems pretty simple but has stumped me thus far.

So to keep it simple lets say I have Users(w/model) and Home controllers, Home is the root route.

In the root directory I want to be able to see all posts made by the User using ajax to update a partial on the home page with the list of posts.

In the users controller I have a def called userposts with this in it

def userposts
  @user = User.find_by_id(params[:id])
  @userposts = @user.posts.all(:order => "created_at DESC")
  respond_to do |format|
    format.js { @userposts}
  end    
end

And in my view I have

<p id="aboutuser">
  <% if @user.about? %>
    <%= "   " + @user.id.to_s %>
  <% else %>
    User has not yet filled this out.
  <% end %>
</p> 
<h3 id="authpostlink">
  <%= link_to "List of all posts", user_userposts_path(@user.id), :id => @user.id, :remote => true %>
</h3>

my errors are as follows

Started GET “/users/2/userposts” for 127.0.0.1 at Sun Jan 15 13:36:23
-0600 2012 Processing by UsersController#userposts as JS Parameters: {“user_id”=>”2”} User Load (0.1ms) SELECT “users”.*
FROM “users” WHERE “users”.”id” IS NULL LIMIT 1 Completed 500 Internal
Server Error in 1ms

NoMethodError (undefined method posts' for nil:NilClass):
app/controllers/users_controller.rb:27:inuserposts’

Rendered
/home/n0de/.rvm/gems/ree-1.8.7-2011.03/gems/actionpack-3.1.0/lib/action_dispatch/middleware/templates/rescues/_trace.erb
(0.8ms) Rendered
/home/n0de/.rvm/gems/ree-1.8.7-2011.03/gems/actionpack-3.1.0/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb
(0.8ms) Rendered
/home/n0de/.rvm/gems/ree-1.8.7-2011.03/gems/actionpack-3.1.0/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (3.2ms)

I do realize i did not post the _show.js.erb file that calls the action to update the div but according to the error messages it doesn’t seem the process has gotten that far.

Answer 1

Assuming you have the following:

# /app/models/user.rb
class User < ActiveRecord::Base
  has_many :posts
end

# /app/models/post.rb
class Post < ActiveRecord::Base
  belongs_to :user
end

I would add a nested resource in your routes file:

#/config/routes.rb
resources :users do
  resources: posts
end

You get a bunch of great “_path” methods for free (run $ rake routes from your console to see them all), and it gives you access to URLs such as /users/123/posts. This request will go to the index method of your PostsController and will automatically include :user_id => 123 in the params hash. You can then do the following:

# In your view:
<%= link_to "List of all posts", user_posts_path(@user), :remote => true %>
<div id="posts"></div>

# /app/controllers/posts_controller.rb
class PostsController < ApplicationController
  respond_to :js # allows for AJAX requests

  def index
    if params[:user_id].present? # Do this if using the nested resource
      @user = User.find(params[:user_id])
      @posts = @user.posts.order('posts.created_at DESC')
    else # Otherwise, treat it like a normal request
      @posts = Post.all
    end
    respond_with @posts
  end
end

Because the your request is sent remotely, you need a corresponding “js” version of your index view (note the file name below and see this Railscast for more explanation):

# /app/views/posts/index.js.erb
$('#posts').html("<%= escape_javascript(render(@posts)) %>");

This will render out the posts into that <div id="posts"> tag. (You’ll probably need a “_post.html.erb” partial in /app/views/posts/” as well.)

However, having said all this, are you sure you need to do this via AJAX? You could simply preload all the posts in the UsersController#show method, initially hide the list using CSS, and then add a jQuery toggle() method on that link. Anyway, hope this makes sense and is helpful.