在Rails中使用连接模型属性有许多:到

用解决

class Group
  has_many :groups_users
  has_many :moderatorships, :class_name => "GroupsUser",:conditions => {:moderator => true}
  has_many :moderators, :through => :moderatorships, :class_name => "User", :source => :user
end

与Matt van Horn的答案相比更可取,因为当我们使用@group.moderator s选择用户信息时,这个答案只产生一个查询,而他的解决方案为每个moderator提供单独的查询。

编辑:更新以回答sizzlepants的问题。用此代码创建的版主在连接模型中应该将版主属性设置为true(Rails使用:创建连接模型时的条件),而且,如果现在必须对其进行编码,我将命名组\用户成员身份以提高可读性。

class User
  has_many :group_users
  has_many :groups, :through => :groups_users
end

class GroupUser
  belongs_to :user
  belongs_to :group
  named_scope :as_moderator, :conditions => "moderator=1"
end

class Group
  has_many :group_users
  has_many :groups, :through => :groups_users
  def moderators
    group_users.as_moderator.map{|gu|gu.user}
  end
end

# use it:
@moderators = @group.moderators
or
@all_mods = Group.all.map{|g|g.moderators}.flatten

蒙基补丁!

class Group < ActiveRecord::Base
   public :with_scope
end