Rails - Jun 2010 - Self Reference, Almost There (I Hope!)

I''m still struggling with the self reference. I *THINK* I''m
getting
close. I have the following tables:

class CreateCategories < ActiveRecord::Migration
  def self.up
    create_table :categories do |t|
    t.string :name, :limit => 40
      t.timestamps
    end
  end
end

class CreateRelationships < ActiveRecord::Migration
  def self.up
    create_table :relationships, :id => false do |t|
    t.integer :category_id
    t.integer :parent_id
    t.integer :sort_order
      t.timestamps
    end
  end
end

My models look like this:

class Relationship < ActiveRecord::Base
  belongs_to :category,  :class_name => ''Category'',
       :foreign_key => ''category_id''
  belongs_to :parent,   :class_name => ''Category'',
             :foreign_key => ''parent_id
end

class Category < ActiveRecord::Base
  has_many :relationships, :foreign_key => ''category_id''

  has_many :parents, :class_name => ''Category'',
                     :through => ''relationships'',
                     :source => :parent

  has_many :children, :class_name => ''Category'',
                      :through => ''relationships'',
                      :source => :category
end

I can create a category. When I try to add a parent to it (e.g.
c.parents << p) I get the error

ActiveRecord::HasManyThroughAssociationNotFoundError: Could not find the
association "relationships" in model Category

I''m sure that I''m missing something simple, but I
don''t see it. Can
anyone let me know what I''m missing?

Thanks much
---Michael
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On 20 June 2010 19:12, Michael Satterwhite
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> class CreateRelationships < ActiveRecord::Migration
>  def self.up
>    create_table :relationships, :id => false do |t|
>    t.integer :category_id
>    t.integer :parent_id
>    t.integer :sort_order
>      t.timestamps
>    end
>  end
> end
If "relationships" is a join table, then it can''t have any
fields
other than the two foreign keys.
> class Relationship < ActiveRecord::Base
>  belongs_to :category,  :class_name => ''Category'',
>       :foreign_key => ''category_id''
>  belongs_to :parent,   :class_name => ''Category'',
>             :foreign_key => ''parent_id
> end
Right - so Relationship is an AR model - it *needs* an ID column.

There might be some other issues... but get to them after the
Relationship models are working (try creating one in the console to
make sure it works...)

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On 20/06/2010 20:18, Michael Pavling wrote:
> On 20 June 2010 19:12, Michael
Satterwhite<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>  wrote:
>> class CreateRelationships<  ActiveRecord::Migration
>>   def self.up
>>     create_table :relationships, :id =>  false do |t|
>>     t.integer :category_id
>>     t.integer :parent_id
>>     t.integer :sort_order
>>       t.timestamps
>>     end
>>   end
>> end
>
> If "relationships" is a join table, then it can''t have
any fields
> other than the two foreign keys.
>
>> class Relationship<  ActiveRecord::Base
>>   belongs_to :category,  :class_name => 
''Category'',
>>        :foreign_key =>  ''category_id''
>>   belongs_to :parent,   :class_name => 
''Category'',
>>              :foreign_key =>  ''parent_id
>> end
>
> Right - so Relationship is an AR model - it *needs* an ID column.
<snip>

Also, you need to refer to the relationships association in the Category 
class as follows:

has_many :parents, :class_name => ''Category'', :through
=>
:relationships, :source => :parent

(In case there''s anybody still interested :) )


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