Rails - Jan 2005 - Request: in_association? method for has_and_belongs_to_many?

Hello

I have a request for the next version of rails.  Could we have an 
in_association?( other_object) for has_and_belongs_to_many 
associations.

I seem to have need for it quite a lot, for instance when I have a User 
object which :has_and_belongs_to_many Group objects.  I wish to check 
whether a User is in a particular Group.

User
	has_and_belongs_to_many :groups

	def in_group?( group_to_check )
			groups.find( group_to_check.id )
		rescue ActiveRecord::RecordNotFound
			false
	end
end

Would be nice to have the template do it automatically.  Unfortunately, 
I can''t quite figure out from the code where these automatic methods 
are created?  If anyone can point me in the right direction I''ll 
happily create a patch.

Thanks

Tom

PS Why does HasAndBelongsToMany.find raise an error if it doesn''t find 
anything, and not just return nil or an empty array?  I prefer errors 
to only take place when something unexpected takes place, rather than 
expected results....

On Thu, Jan 06, 2005 at 08:06:24PM +0000, Thomas Counsell
wrote:
> I have a request for the next version of rails.  Could we have an 
> in_association?( other_object) for has_and_belongs_to_many 
> associations.
> 
> I seem to have need for it quite a lot, for instance when I have a User 
> object which :has_and_belongs_to_many Group objects.  I wish to check 
> whether a User is in a particular Group.
> 
> User
>   has_and_belongs_to_many :groups
> 
>   def in_group?( group_to_check )
>           groups.find( group_to_check.id )
>       rescue ActiveRecord::RecordNotFound
>           false
>   end
> end
> 
> Would be nice to have the template do it automatically.  Unfortunately, 
The record''s associations are simply an array of AR objects so you can
use Array#include?

e.g.
    
    some_user.groups.include? some_group

hope this helps,
marcel
-- 
Marcel Molina Jr. <marcel-WRrfy3IlpWYdnm+yROfE0A@public.gmane.org>

> >   def in_group?( group_to_check )
> >           groups.find( group_to_check.id )
> >       rescue ActiveRecord::RecordNotFound
> >           false
> >   end
> > end
> >
> > Would be nice to have the template do it automatically. 
Unfortunately,
> 
> The record''s associations are simply an array of AR objects so you
can
> use Array#include?
> 
> e.g.
> 
>     some_user.groups.include? some_group
> 
Although we could use include, it''d be clearer from the template
designer''s perspective to use in_group?

Of course, it''s not hard to add that in a base model which you add
that method :-) Ah the glory of ruby.

-rabble