class User < ActiveRecord::Base
   has_many :memberships
   has_many :accounts, :through => :memberships, :source => 'membershipable', :source_type => 'Account'
   has_many :projects, :through => :memberships, :source => 'membershipable', :source_type => 'Project'
end

class Account < ActiveRecord::Base
  has_many :memberships, :as => :membershipable
  has_many :users, :through => :memberships
end

class Project < ActiveRecord::Base
  has_many :memberships, :as => :membershipable
  has_many :users, :through => :memberships
end

class Membership < ActiveRecord::Base
  belongs_to :user
  belongs_to :membershipable, :polymorphic => true
end

代码很简单，需求就是把 account 和 project 所属的用户都记录在 membership 中。

User.first.projects << Project.first 不工作 NameError: uninitialized constant Membership::Membershipable

不知道大家在 rails 3.1.1 下用 has_many :through 和 Polymorphic Associations 是否出现过这样的问题？

我记得在以前的 rails 版本中是支持的。今天发现 3.1.1 不支持了，feature or bug?