Question

我有两个模特，会议和与会者，他们有着共同的关系。我还有一个会议可以属于的用户模型（作为会议组织者）。

class Meeting < ActiveRecord::Base
  belongs_to :organizer, :class_name => User, :foreign_key => "organizer_id"
  has_and_belongs_to_many :attendees, :class_name => User, :association_foreign_key => "attendee_id"
end

class User < ActiveRecord::Base
  has_and_belongs_to_many :meetings, :class_name => Meeting, :association_foreign_key => "meeting_id"
end

然后我有关系表..

create_table "attendees_meetings", :id => false, :force => true do |t|
  t.integer "attendee_id"
  t.integer "meeting_id"
end

当我创建新会议，然后将与会者引用为meeting.attendees时，我收到错误消息。与组织者相同的是，meeting.organizer会抛出错误。我没有正确设置关系吗？

m = Meeting.create(:subject => "Test", :location => "Neverland", :body => "A test", :organizer_id => 8)
m.organizer
NoMethodError: undefined method `match' for #<Class:0x00000103d8cf08>

与与会者一样（虽然我目前没有定义任何内容，但不应该抛出错误）

1.9.2-p318 :014 > m.attendees
(Object doesn't support #inspect)
=>

Answer 1

class_name上的has_and_belongs_to_many选项应该是一个字符串，它是该类的名称。您已经传递了类对象本身。所以，例如，

has_and_belongs_to_many :attendees, 
    :class_name => "User", 
    :association_foreign_key => "attendee_id"

我认为您可能还需要在:foreign_key => 'attendee_id'模型的has_and_belongs_to_many声明中添加User，并可以删除:association_foreign_key选项，因为它是默认设置。实际上你也可能失去:class_name选项，因为这也是默认选项。所以：

has_and_belongs_to_many :meetings, 
    :foreign_key => "attendee_id"

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