Rails 4中的ActiveRecord::AssociationTypeMismatch

Question

我正在尝试向连接表user_logs添加一条记录，该连接表连接了user_actions和users。但是，当我尝试使用以下代码添加项目时，会收到下面的错误消息。为什么会出现这个错误？为参考，我已经包含了模型和模式如下。

2.0.0-p353 :001 > user = User.first
2.0.0-p353 :002 > action = UserAction.first
2.0.0-p353 :003 > user.user_logs
UserLog Load (0.3ms)  SELECT `user_logs`.* FROM `user_logs` WHERE `user_logs`.`user_id` = 1
=> #<ActiveRecord::Associations::CollectionProxy []> 
2.0.0-p353 :004 > user.user_logs << action
(0.3ms)  BEGIN
(0.2ms)  ROLLBACK
ActiveRecord::AssociationTypeMismatch: UserLog(#2156995120) expected, got UserAction(#2177269140)

用户模型

class User < ActiveRecord::Base
   ...
   has_many :user_logs
   has_many :user_actions, :through => :user_logs
end

用户操作模型

class UserAction < ActiveRecord::Base
   has_many :user_logs
   has_many :users, :through => :user_logs
end

用户日志模型

class UserLog < ActiveRecord::Base
  belongs_to :user
  belongs_to :user_action
end

架构

create_table "user_actions", force: true do |t|
  t.string   "action",     limit: 40, default: "", null: false
  t.datetime "created_at"
  t.datetime "updated_at"
end

add_index "user_actions", ["action"], name: "index_user_actions_on_action", unique: true, using: :btree

create_table "user_logs", force: true do |t|
  t.integer  "user_id"
  t.integer  "user_action_id"
  t.datetime "created_at"
  t.datetime "updated_at"
end

- evanvee

---

我确保在config/environments/test.rb中将cache_classes设置为true：https://dev59.com/CG025IYBdhLWcg3whWdm。但这并没有解决问题。 - evanvee

Answer 1

你正在尝试将UserAction对象添加到UserLog集合中，这肯定会引发TypeMismatch错误。请改为使用以下方法：

user = User.first
action = UserAction.first
user.user_actions << action
user.save

- shinnc