ruby-on-rails – 无法找到源关联：Rails 3.2中模型关系中的foll

“ActiveRecord::HasManyThroughSourceAssociationNotFoundError in Pages#home”
“Could not find the source association(s) :followed_id in model Relationship. Try ‘has_many :followed_users,:through => :relationships,:source => ‘. Is it one of :follower or :followed?”

这真的很奇怪,因为我完全按照教程的说明进行操作.我甚至复制粘贴每个代码片段.

我的用户模型(摘录)：

class User < ActiveRecord::Base 

    has_many :relationships,foreign_key: "follower_id",dependent: :destroy
    has_many :followed_users,through: :relationships,source: "followed_id"

    has_many :reverse_relationships,foreign_key: "followed_id",class_name: "Relationship",dependent: :destroy
    has_many :followers,through: :reverse_relationships,source: :follower

我的关系模型：

class Relationship < ActiveRecord::Base
    attr_accessible :followed_id

    belongs_to :follower,class_name: "User"
    belongs_to :followed,class_name: "User"

    validates :follower_id,presence: true
    validates :followed_id,presence: true
  end

我的迁移文件：

class CreateRelationships < ActiveRecord::Migration
    def change
      create_table :relationships do |t|
        t.integer :follower_id
        t.integer :followed_id

        t.timestamps
      end

      add_index :relationships,:follower_id
      add_index :relationships,:followed_id
      add_index :relationships,[:follower_id,:followed_id],unique: true
    end
  end

我一直试图解决这个问题,但我根本不知道问题可能是什么(从教程中准确复制代码).