I have a model layer containing Movie, Person, Role, and RoleType,
making it possible to express facts such as "Clint Easterbunny is
director of the movie Gran Milano".
The relevant model and associations look like this
class Movie < ActiveRecord::Base
has_many :roles, :include => :role_type, :dependent => :destroy
has_many :participants, :through => :roles, :source => :person do
def as(role_name)
self.scoped(
:joins => 'CROSS JOIN role_types',
:conditions => [
"(roles.role_type_id = role_types.id) +
" AND role_types.name = ?",
role_name
]
)
end
end
...
end
Querying is easy:
m = Movie.find_by_title('Gran Milano')
m.participants.as('director')
However, changing relations is painful. It's already bad with has_many
:through associations when the intermediate model is not completely
dumb, and my scope trickery doesn't make it any better.
Now, let's assume for a moment that participants was a plain has_many
association. Then it would be possible to write things like
m.participants.clear
m.participants << Person.find_by_name('Steve McKing')
m.participant_ids = params[:movie][:participants]
With the given has_many :through, none of these work, as Role object
won't validate without a role type. Anyway, what I would like to write
is
m.participants.as('actor').clear
m.participants.as('actor') << Person.find_by_name('Steve McKing')
m.participants.as('actor') = Person.find(params[:movie][:participants])
I'm not sure this is possible with ActiveRecord as it is, but I'm
looking forward to suggestions.
Michael
--
Michael Schuerig
mailto:[email protected]
http://www.schuerig.de/michael/
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups "Ruby
on Rails: Talk" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---
