Rails has_many :through with conditions and building associations

问题

I'm having problems building an association that is a has_many :through with conditions. I have this model:

class Contact < AR
  has_many :group_contacts
  has_many :groups, :through => :group_contacts, :conditions => {:groups => {:published => true}}
end

problem happens when I try to instantiate a group from a contact. With the above syntax, I get an error:

contact.groups.build
=> ActiveRecord::UnknownAttributeError: unknown attribute: groups

But when I use the following syntax it works:

has_many :groups, :through => :group_contacts, :conditions => ['groups.published = ?', true]

contact.groups.build
=> #<Group id: nil, name: nil, description: nil, created_at: nil, updated_at: nil, published: true>

I see a reference to the exact problem in this question. It is said a ticket would be filed for this bug (back in pre- rails 3 versions). I can't find anything however on rails 3.0.x.

I'm using 3.0.8. Has anyone else found this issue?

Further Notes:

I've also found that when I'm building groups, it actually ignores my conditions on the association when building. The only reason my above build had published => true is because it's the default in the db.

This seems like a regression, can anyone else verify this?

回答1:

has_many :groups, :through => :group_contacts, :conditions => {:published => true}

or

has_many :groups, :through => :group_contacts, :conditions => {"groups.published" => true}

来源：https://stackoverflow.com/questions/7067907/rails-has-many-through-with-conditions-and-building-associations