Rails - Aug 2005 - strange difference between has_one and has_many

Hi,

I don''t know rails enough to decide wether this is a bug or feature.

I have two models, Menu and MenuText (many langs, so many texts per
menu). (see sql below)

If I define has_many:

class Menu < ActiveRecord::Base
    has_many :menu_texts, :conditions => [''lang = ?'',
''fr'']
end
class MenuText < ActiveRecord::Base
    belongs_to :menu
end

then
  Menu.find(1).menu_texts.first shows the unique menu_text associated to
the menu.
no pb, everything works.

But if I change to has_one:
class Menu < ActiveRecord::Base
    has_one :menu_text, :conditions => [''lang = ?'',
''fr'']
end

then
  Menu.find(1).menu_text raises an error (array to string conversion)

It''s due to the difference of treatment that conditions receive in both
associations code:

  active_record/associations/has_many_association.rb:
    @finder_sql << " AND #{interpolate_sql(@conditions)}" if
@conditions

  active_record/associations/has_one_association.rb, li 68:
    #{@options[:conditions] ? " AND " + @options[:conditions].

Why does has_one treat conditions differently?
Isn''t it a bug ?


SQL:
CREATE TABLE menus (
  id BIGSERIAL NOT NULL,
  -- Some statistics about the user data
  created_at TIMESTAMP NOT NULL,
  updated_at TIMESTAMP NOT NULL,
  ...
  PRIMARY KEY (id),
  FOREIGN KEY (parent_id) REFERENCES menus (id) ON DELETE RESTRICT
);

CREATE TABLE menu_texts (
  id BIGSERIAL NOT NULL,
  menu_id BIGINT NOT NULL,
  -- Real information: lang, title
  lang CHARACTER (2) NOT NULL DEFAULT ''fr'',
  title CHARACTER VARYING (200) NOT NULL,
  FOREIGN KEY (menu_id) REFERENCES menus (id) ON DELETE CASCADE
);

-- 
Jean-Christophe Michel

Jean-Christophe Michel wrote:
>Hi,
>
>I don''t know rails enough to decide wether this is a bug or
feature.
>
>  
>
Feature.
>I have two models, Menu and MenuText (many langs, so many texts per
>menu). (see sql below)
>
>If I define has_many:
>
>class Menu < ActiveRecord::Base
>    has_many :menu_texts, :conditions => [''lang = ?'',
''fr'']
>end
>class MenuText < ActiveRecord::Base
>    belongs_to :menu
>end
>
>then
>  Menu.find(1).menu_texts.first shows the unique menu_text associated to
>the menu.
>no pb, everything works.
>
>  
>
You said there are many, so menu_texts (note the plural) returns an array.
>But if I change to has_one:
>class Menu < ActiveRecord::Base
>    has_one :menu_text, :conditions => [''lang = ?'',
''fr'']
>end
>
>then
>  Menu.find(1).menu_text raises an error (array to string conversion)
>
>  
>
You said it has one, so menu_text (no plural) returns a single object.
>It''s due to the difference of treatment that conditions receive in
both
>associations code:
>
>  active_record/associations/has_many_association.rb:
>    @finder_sql << " AND #{interpolate_sql(@conditions)}" if
@conditions
>
>  active_record/associations/has_one_association.rb, li 68:
>    #{@options[:conditions] ? " AND " + @options[:conditions].
>
>Why does has_one treat conditions differently?
>  
>

Hi Steve

I''m not sure you got my point ;-)

Steve Downey wrote:
>> I have two models, Menu and MenuText (many langs, so many texts per
>> menu). (see sql below)
>>
>> If I define has_many:
>>
>> class Menu < ActiveRecord::Base
>>    has_many :menu_texts, :conditions => [''lang =
?'', ''fr'']
>> end
>> class MenuText < ActiveRecord::Base
>>    belongs_to :menu
>> end
>>
>> then
>>  Menu.find(1).menu_texts.first shows the unique menu_text associated to
>> the menu.
> You said there are many, so menu_texts (note the plural) returns an array.
Sure, as I wrote: >> no pb, everything works.
>> But if I change to has_one:
>> class Menu < ActiveRecord::Base
>>    has_one :menu_text, :conditions => [''lang = ?'',
''fr'']
>> end
>>
>> then
>>  Menu.find(1).menu_text raises an error (array to string conversion)
> You said it has one, so menu_text (no plural) returns a single object.
No! It raises an error, array to string conversion, whereas of course
I''d like to see an object.
The error disappear if I replace
  :conditions => [''lang = ?'', ''fr'']
by
  :conditions => [''lang = fr'']

so the reason is clearly in the way conditions are handled.
>> It''s due to the difference of treatment that conditions
receive in both
>> associations code:
>>
>>  active_record/associations/has_many_association.rb:
>>    @finder_sql << " AND
#{interpolate_sql(@conditions)}" if @conditions
>>
>>  active_record/associations/has_one_association.rb, li 68:
>>    #{@options[:conditions] ? " AND " + @options[:conditions].
>>
>> Why does has_one treat conditions differently?

-- 
Jean-Christophe Michel