Rails:为什么"has_many ...,:through => ..."关联导致"NameError:uninitialized constant ..."

Question

为了表示一个组可以拥有多个用户,并且一个用户可以属于多个组,我设置了以下关联:

class Group < ActiveRecord::Base
  has_many :users_groups
  has_many :users, :through => :users_groups
end

class User < ActiveRecord::Base
  has_many :users_groups
  has_many :groups, :through => :users_groups
end

class UsersGroups < ActiveRecord::Base
  belongs_to :user
  belongs_to :group
end

但是,当我键入:

Group.find(1).users

我明白了:

NameError: uninitialized constant Group::UsersGroup

我究竟做错了什么 ？

Answer 1

class UsersGroups应该是class UsersGroup.ActiveRecord模型是单数 - 表格是复数.