Nesting resource

Question

I'm trying to nest my messages controller into my channels controller. But when I go to my messages view i get the error "couldn't find channel with no id"

 class MessagesController < ApplicationController

  def index
    @channel = Channel.find(params[:channel_id])
    @messages = @channel.messages
  end

  def new
    @channel = Channel.find(params[:channel_id])
    @message = @channel.messages.build
  end

  def create
    @channel = Channel.find(params[:channel_id])
    @message = @channel.messages.build(params[:message])
    if @message.save
      flash[:notice] = "Successfully created message."
      redirect_to channel_url(@message.channel_id)
    else
      render :action => 'new'
    end
  end

  def edit
    @message = Message.find(params[:id])
  end

  def update
    @message = Message.find(params[:id])
    if @message.update_attributes(params[:message])
      flash[:notice] = "Successfully updated message."
      redirect_to channel_url(@message.channel_id)
    else
      render :action => 'edit'
    end
  end

  def destroy
    @message = Message.find(params[:id])
    @message.destroy
    flash[:notice] = "Successfully destroyed message."
    redirect_to channel_url(@message.channel_id)
  end
end

Channels controller

class ChannelsController < ApplicationController

  def index
    @channels = Channel.find(:all)
  end

  def show
    @channel = Channel.find(params[:id])
    @message = Message.new(:channel => @channel)
  end

  def new
    @channel = Channel.new
  end

  def create
    @channel = Channel.new(params[:channel])
    if @channel.save
      flash[:notice] = "Successfully created channel."
      redirect_to @channel
    else
      render :action => 'new'
    end
  end

  def edit
    @channel = Channel.find(params[:id])
  end

  def update
    @channel = Channel.find(params[:id])
    if @channel.update_attributes(params[:channel])
      flash[:notice] = "Successfully updated channel."
      redirect_to @channel
    else
      render :action => 'edit'
    end
  end

  def destroy
    @channel = Channel.find(params[:id])
    @channel.destroy
    flash[:notice] = "Successfully destroyed channel."
    redirect_to channels_url
  end
end

routes.rb

   SeniorProject::Application.routes.draw do

  resources :users
  resources :channels, :shallow => true do |channels|
    channels.resources :messages
  end

  root :channels

  resources :users, :user_sessions

  match 'login' => 'user_sessions#new', :as => :login
  match 'logout' => 'user_sessions#destroy', :as => :logout
  match ':controller(/:action(/:id(.:format)))'

end

Answer 1

What's going on here is that this line:

@channel = Channel.find(params[:channel_id])

Is falling over because there's no defined channel_id in the params hash. I see you're using shallow routes, which means your uri probably looks like this:

/messages

And you need it to look like:

/channels/1/messages

Try changing your url to be:

channel_messages_url(@channel)

instead of

messages_url

This is a guess btw, it could be because of the way you've defined your routes.rb, which looks a little odd because you're defining the messages routes twice, once with the has_many and again as a proper resource. You probably want something like:

# assuming you need shallow routes
resources :channels, :shallow => true do |channels|
  channels.resources :messages
end