Question

I have the following classes:

class VideoChannel < ActiveRecord::Base

  #Associations
  belongs_to :video_playlist, :dependent => :destroy
  VideoChannel.video_playlist_name 

  delegate :name, :id, :list_type, :list_id, :manual, :to => :video_playlist, :prefix => true

  #validations
  validates_presence_of :name

  #After Functions
  def after_create
    video_playlist = VideoPlaylist.new(:name      => self.name,
                                       :list_type => "VideoChannel",
                                       :list_id   => self.id)
    video_playlist.save
  end

And :

class VideoPlaylist < ActiveRecord::Base
  belongs_to  :list, :polymorphic => true

  has_many    :video_channels, :dependent => :destroy
  delegate :name, :id, :description, :to => :video_channel, :prefix => true

end

I’m trying to use the Rails Delegate function to create a link in the VideoChannel page that allows me to to link to the Video Playlist and edit the contents there. So the association is there and You can currently edit the playlists by going through the playlists section but we want to combine them. I can’t seem to figure this out. Im also very new to Rails, still working through the guides etc.

Edit: Here’s the view code

<%= link_to '<span class="pen icon"></span>Edit',
      content_url(:controller =>"video_playlists", :id => channel.video_playlist_id, :action => "edit"),
      :class => "button right" %>

Here are teh relevant pieces of the controllers:

class VideoChannelsController < ApplicationController
  # GET /videochannels
  # GET /videochannels.xml
  def index

    @video_channels = VideoChannel.roots(:order => 'order_num')
    @video_channels_parents = @video_channels.group_by {:parent_id}
    respond_to do |format|
      format.html # index.html.erb
      format.xml  { render :xml => @video_channels }
    end

  end

  # GET /videochannels/1
  # GET /videochannels/1.xml
  def show
    @video_channel = VideoChannel.find(params[:id], :order => 'order_num')

    respond_to do |format|
      format.html # show.html.erb
      format.xml  { render :xml => @video_channel }
    end
  end

end

class VideoPlaylistsController < ApplicationController
  # GET /video_playlists
  # GET /video_playlists.xml
  def index
    if !params[:with].nil?
      @video_playlists = VideoPlaylist.find(:all, :conditions => {:list_type => 'VideoShow'})
    else
      @video_playlists = VideoPlaylist.find(:all, :conditions => {:list_type => 'Section'})
    end

    respond_to do |format|
      format.html # index.html.erb
      format.xml  { render :xml => @video_playlists }
    end
  end

  # GET /video_playlists/1
  # GET /video_playlists/1.xml
  def show
    @video_playlist = VideoPlaylist.find(params[:id], :include => [{:video_video_playlists => :video}, {:videos => :asset}, {:videos => :content_image}])

    respond_to do |format|
      format.html # show.html.erb
      format.xml  { render :xml => @video_playlist }
    end
  end
end

Answer 1

Where did the line

VideoChannel.video_playlist_name

Come from? What’s it doing? You’re also calling a method on the class not an instance (sort of – Ruby isn’t quite like this, but it’s enough to explain).

Anyway:

Delegate is really for avoiding lots of train wreck code like this:

fred.jim.bill.xxx

You’ve said that they belong to each other – the relationships look like they’re the wrong way round. Why are you creating the parent from inside the child? How are you going to have many video channels belonging to a given playlist?

I think you need to look at build and the relationship names. To gat past me maybe misunderstanding your model, lets have switch to a product that has many stock items:

class Product < ActiveRecord::Base
  has_many :stock_items
end

class StockItem < ActiveRecord::Base
  belongs_to :product
end

This means that stock_item will have a column product_id.

So, say you’re creating a product you’d do something like:

product.stock_items.build # :whatever the params are required

This automatically sets the id’s for you and means you don’t have to set id’s. Then when you do product.save it will save all the related stock items too.

And in the view for this toy model, then if you were displaying one of the stock items, you’d use delegate to show the name of the product in the view without having to do lost of stock_item.product.name (for example).

I hope this helps.