ruby-on-rails - rails : Why "has_many ..., :through => ..." association results in "NameError: uninitialized constant ..."

Question

为了表达一个组可以有多个用户，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，当我输入:

Group.find(1).users

我得到:

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。