Ruby on rails 3 MongoID多对多关系

我有两个模型，它们有以下关系：

Class User
has_and_belongs_to_many :notification_channels

Class NotificationChannel
has_and_belongs_to_many :users

我能够以这种方式为用户对象添加通知通道

@user.notification_channels << @notification

如何从用户频道中删除频道？

以下是解决方案

 @user.notification_channels -= [NotificationChannel.find_by(id: params[:channel_id])] # relationship is removed both ways and both objects are saved

或

我会成功的

 @user.notification_channels -= [NotificationChannel.find_by(id: params[:channel_id])] # relationship is removed both ways and both objects are saved

 @user.notification_channels.delete(NotificationChannel.find_by(id: params[:channel_id])) # relationship is removed both ways but @user needs to be saved manually
 @user.save