Rails - Mar 2006 - Multiple polymorphic belongs_to declarations

I have the following models:

    class Card < ActiveRecord::Base
      belongs_to :deck
      belongs_to :front, :polymorphic => true
      belongs_to :back, :polymorphic => true
    end

    class TextContent < ActiveRecord::Base
      has_one :card, :as => :front
      has_one :card, :as => :back
    end

The conflicting has_one declarations don''t work. What I need is a way
to
name the belongs_to associations ''front'' and
''back'', but have them go
through a single interface, which the TextContent model can reference, 
like:

    class Card < ActiveRecord::Base
      belongs_to :deck
      belongs_to :front, :polymorphic => true, :interface => :content
      belongs_to :back, :polymorphic => true, :interface => :content
    end

    class TextContent < ActiveRecord::Base
      has_one :card, :as => :content
    end

Is this possible? Or is there some other way I should relate these 
models?

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On Sunday, March 19, 2006, at 9:52 PM, Thomas Jack
wrote:
>I have the following models:
>
>    class Card < ActiveRecord::Base
>      belongs_to :deck
>      belongs_to :front, :polymorphic => true
>      belongs_to :back, :polymorphic => true
>    end
>
>    class TextContent < ActiveRecord::Base
>      has_one :card, :as => :front
>      has_one :card, :as => :back
>    end
>
>The conflicting has_one declarations don''t work. What I need is a
way to
>name the belongs_to associations ''front'' and
''back'', but have them go
>through a single interface, which the TextContent model can reference,
>like:
>
>    class Card < ActiveRecord::Base
>      belongs_to :deck
>      belongs_to :front, :polymorphic => true, :interface => :content
>      belongs_to :back, :polymorphic => true, :interface => :content
>    end
>
>    class TextContent < ActiveRecord::Base
>      has_one :card, :as => :content
>    end
>
>Is this possible? Or is there some other way I should relate these
>models?
>
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>Posted via http://www.ruby-forum.com/.
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>Rails mailing list
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Could you supply the following to help with the discussion:
a) your schema for these tables,
b) what do you mean by "doesn''t work"? are you getting an
error, or the
behavior isn''t what you expect, etc.

adam

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adam ingramgoble wrote:
> Could you supply the following to help with the discussion:
> a) your schema for these tables,
    create_table :cards do |t|
      t.column :deck_id, :integer, :null => false
      t.column :front_id, :integer, :null => false
      t.column :front_type, :string, :null => false
      t.column :back_id, :integer, :null => false
      t.column :back_type, :string, :null => false
    end

    create_table :decks do |t|
      t.column :title, :string, :null => false
      t.column :created_at, :datetime, :null => false
    end

    create_table :text_contents do |t|
      t.column :content, :text, :null => false
    end
> b) what do you mean by "doesn''t work"? are you getting
an error, or the
> behavior isn''t what you expect, etc.
The polymorphic belongs_to declarations work fine. I can do things like 
@card.front = TextContent.new(:content => "some text") and the 
front_type and front_id work properly.

However, the two has_one declarations conflict. They both expose a card 
attribute, so the second has_one just overrides the first. Consider the 
following console session, for example:

    Loading development environment.
    >> front = TextContent.new(:content => ''front of
card'')
    => #<TextContent:0x382a800 @new_record=true, 
@attributes={"content"=>"front of card"}>
    >> back = TextContent.new(:content => ''back of
card'')
    => #<TextContent:0x381e908 @new_record=true, 
@attributes={"content"=>"back of card"}>
    >> card = Card.new(:front => front, :back => back)
    => #<Card:0x3817870 @new_record=true,
@front=#<TextContent:0x382a800
@new_record=true, @attributes={"content"=>"front of
card"}>,
#attributes={"front_id"=>0, "deck_id"=>0,
"back_type"=>"", "back_id"=>0,
"front_type"=>""}, @back=#<TextContent:0x381e908
@new_record=true,
@attributes={"content"=>"back of card"}>>
    >> card.save
    => true
    >> card.front
    => #<TextContent:0x382a800 @new_record=true, 
@attributes={"content"=>"front of card"}>
    >> card.back
    => #<TextContent:0x381e908 @new_record=true, 
@attributes={"content"=>"back of card"}>
    >> card.front.card
    => nil
    >> card.back.card
    => #<Card:0x37e5698 @attributes={"id"=>"2",
"front_id"=>"3",
"deck_id"=>"0",
"back_type"=>"TextContent",
"back_id"=>"4",
"front_type"=>"TextContent"}>

Note that the .front and .back attributes of the Card model work fine, 
but that only the second has_one works for the TextContent model.

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