Question

This seems like a bug in Rails to me, but there’s probably not much I can do about that. So how can I accomplish my expected behavior?

Suppose we have:

class User < ActiveRecord::Base
  has_many :awesome_friends, :class_name => "Friend", :conditions => {:awesome => true}
end

And execute the code:

>> my_user.awesome_friends << Friend.new(:name=>'jim')

Afterwards, when I inspect this friend object, I see that the user_id field is populated. But I would also expect to see the “awesome” column set to ‘true’, which it is not.

Furthermore, if I execute the following from the console:

>> my_user.awesome_friends << Friend.new(:name=>'jim')
>> my_user.awesome_friends
= [#<Friend id:1, name:"jim", awesome:nil>]
# Quit and restart the console
>> my_user.awesome_friends
= []

Any thoughts on this? I suppose the conditions hash could be arbitrarily complex, making integration into the setter impossible. But in a way it feels like by default we are passing the condition “:user_id => self.id”, and that gets set, so shouldn’t others?

Thanks,
Mike

EDIT:

I found that there are callbacks for has_many, so I think I might define the relationship like this:

has_many :awesome_friends,
         :class_name => "Friend",
         :conditions => {:awesome => true},
         :before_add => Proc.new{|p,c| c.awesome = true},
         :before_remove => Proc.new{|p,c| c.awesome = false}

Although, it’s starting to feel like maybe I’m just implementing some other, existing design pattern. Maybe I should subclass AwesomeFriend < Friend? Ultimately I need a couple of these has_many relationships, and subclassing get’s messy with all the extra files..

EDIT 2:

Okay, thanks to everyone who commented! I ultimately wrapped up the method above into a nice little ActiveRecord extension, ‘has_many_of_type’. Which works like follows:

has_many_of_type :awesome_friends, :class_name => "Friend", :type=>:awesome

Which just translates to has_many with the appropriate conditions, before_add, and before_remove params (and it assumes the existence of a column named friend_type).

Answer 1

You need use:

my_user.awesome_friends.create(:name=>'jim') or my_user.awesome_friends.build(:name=>'jim')

In documentation:
has_many (:conditions)

Record creations from the association are scoped if a hash is used. has_many :posts, :conditions => {:published => true} will create published posts with @blog.posts.create or @blog.posts.build.