Rails - Sep 2005 - ActiveRecord "contains" relationship

I don''t know if I have missed something in the documentation, but I
have
been trying to create a relationship between a couple of models that I can
only describe as a "contains" relationship.

The simplified objects are:

 themes
  - id INT
  - name VARCHAR
  ...
  - main_color_id INT
  - secondary_color_id INT
 
 colors
  - id INT
  - red INT
  - green INT
  - blue INT

I would like to create a relationship between 
    parent.green_child_id -> child.id and 
    parent.blue_child_id -> child.id

such that I would be able to use the expression "theme.main_color.red"
and "theme.secondary_color.red".

Is that currently possible or would there need to be a new kind of
relationship created?

thanks.

e.

Hello,

I think you can just do it like this (not tested):

class Themes
  belongs_to :main_color, :class_name => "Color"
  belongs_to :secondary_color, :class_name => "Color"
.
.
.
end

Not really sure what you wanted to say with:
<snip>
I would like to create a relationship between
   parent.green_child_id -> child.id and
   parent.blue_child_id -> child.id
</snip>
Hope it helps :-)

On 9/6/05, eric lindvall <eric@5stops.com> wrote:
> I don't know if I have missed something in the documentation, but I
have
> been trying to create a relationship between a couple of models that I can
> only describe as a "contains" relationship.
> 
> The simplified objects are:
> 
>  themes
>   - id INT
>   - name VARCHAR
>   ...
>   - main_color_id INT
>   - secondary_color_id INT
> 
>  colors
>   - id INT
>   - red INT
>   - green INT
>   - blue INT
> 
> I would like to create a relationship between
>     parent.green_child_id -> child.id and
>     parent.blue_child_id -> child.id
> 
> such that I would be able to use the expression
"theme.main_color.red"
> and "theme.secondary_color.red".
> 
> Is that currently possible or would there need to be a new kind of
> relationship created?
> 
> thanks.
> 
> e.
> 
> 
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
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Hello Eric,

eric lindvall said the following on 2005-09-06 03:48:
> The simplified objects are:
> 
>  themes
>   - id INT
>   - name VARCHAR
>   ...
>   - main_color_id INT
>   - secondary_color_id INT
>  
>  colors
>   - id INT
>   - red INT
>   - green INT
>   - blue INT
This is a has_one relationship in Rails.  So,
class Theme
   has_one :main_color, :class_name => ''Color''
   has_one :secondary_color, :class_name => ''Color''
end

class Color
end

ActiveRecord::Associations::ClassMethods#has_one
http://api.rubyonrails.com/classes/ActiveRecord/Associations/ClassMethods.html#M000428

Hope that helps !
François

> Not really sure what you wanted to say with:
> <snip>
> I would like to create a relationship between
>    parent.green_child_id -> child.id and
>    parent.blue_child_id -> child.id
> </snip>
Yeah.. it was late and I changed the example half way through writing.

It should have been

  themes.main_color_id -> colors.id
  themes.secondary_color_id -> colors.id

That''s funny that you would use a ''belongs_to''
relationship for something
that ''contains'' something else.

I tried using a ''has_on'' relationship but the problem with
thas is it
expects to find a column ''colors.theme_id'' which does not
exist (and
doesn''t make sense, because there is more than one linkage between
''themes'' and ''colors'').

If I use a ''belongs_to'', it seems that I am not able to say:

  theme.main_color.red = 5

which seems to make sense with the documentation.

I''ve also tried

  theme.create_main_color(:red => 5)

which creates the entry in the ''colors'' table, but does not
assign the
''colors.id'' to ''themes.main_color_id''. (I
see the UPDATE happen on the
''themes'' table, but main_color_id is always set to NULL)

Am I still doing something wrong?

thanks.

e.


On Tue, 06 Sep 2005, pepe wrote:
> Hello,
> 
> I think you can just do it like this (not tested):
> 
> class Themes
>   belongs_to :main_color, :class_name => "Color"
>   belongs_to :secondary_color, :class_name => "Color"
> .
> .
> .
> end