Ruby on Rails 3 模型之间的关系

Question

我正在关注为 Rails 3 制作的教程，我正在使用 Rails 3.2，但我认为我正确地遵循它但出现错误，我的课程如下，当我使用 task.admin_users_tasks 时发生错误

class Task < ActiveRecord::Base

  attr_accessible :name, :project_id, :task_id, :permalink, :visible, :position, :created_at
  belongs_to :project
  has_and_belongs_to_many :admin_users
  has_many :admin_users_tasks
end

class AdminUsersTask < ActiveRecord::Base
  attr_accessible :admin_user_id, :task_id, :created_at, :updated_at
  belongs_to :admin_user, :class_name => "AdminUser" :foreign_key => 'admin_user_id'
  belongs_to :task
end

class AdminUser < ActiveRecord::Base

  attr_accessible :first_name, :last_name, :username, :email

  has_and_belongs_to_many :projects
  has_and_belongs_to_many :tasks
  has_many :admin_users_tasks
  has_many :admin_users_projects
end

Rails 控制台

    1.9.3-p362 :032 > task
 => #<Task id: 1, project_id: 6, permalink: "taskytask", position: 1, visible: true,   created_at: "2013-02-21 05:08:01", updated_at: "2013-02-21 05:08:01", name: "Task Name for   Noname Project"> 
1.9.3-p362 :033 > me
 => #<AdminUser id: 1, first_name: "Larry", last_name: "David", email:         "larry.david@mail.com", hashed_password: "c9f4e8d3aaa265033c2f517abd5d347bd81d67fa",     created_at: "2013-02-21 04:43:20", updated_at: "2013-02-21 04:43:20", username: "larrydavid",     salt: "d4189f8db685776d3a3c3c4d0700786b7879362d"> 
1.9.3-p362 :034 > me.admin_users_tasks
 => [] 
1.9.3-p362 :035 > task.admin_users_tasks
NoMethodError: undefined method `admin_users_tasks' for #<Task:0x007fca9e159f58>
    from /Users/larrydavid/.rvm/gems/ruby-1.9.3-p362/gems/activemodel-    3.2.11/lib/active_model/attribute_methods.rb:407:in `method_missing'
    from /Users/larrydavid/.rvm/gems/ruby-1.9.3-p362/gems/activerecord-    3.2.11/lib/active_record/attribute_methods.rb:149:in `method_missing'
    from (irb):35
        from /Users/larrydavid/.rvm/gems/ruby-1.9.3-p362/gems/railties-    3.2.11/lib/rails/commands/console.rb:47:in `start'
    from /Users/larrydavid/.rvm/gems/ruby-1.9.3-p362/gems/railties-    3.2.11/lib/rails/commands/console.rb:8:in `start'
    from /Users/larrydavid/.rvm/gems/ruby-1.9.3-p362/gems/railties-    3.2.11/lib/rails/commands.rb:41:in `<top (required)>'
    from script/rails:6:in `require'
from script/rails:6:in `<main>'
1.9.3-p362 :036 > 

Answer 1

该代码有点尴尬，主要是因为您使用 HABTM 语法以及提供模型，您应该使用 has_many :through 来完成。我会以不同的方式设置模型，然后 rails 可能不会那么混乱。

class Task < ActiveRecord::Base
  has_many :admin_users_tasks
  has_many :admin_users, :through => :admin_users_tasks
end

class AdminUser < ActiveRecord::Base
  has_many :admin_users_tasks
  has_many :tasks, :through => :admin_users_tasks
end

class AdminUserTasks < ActiveRecord::Base
  belongs_to :admin_user
  belongs_to :task
end

HABTM 适用于您需要多对多连接的情况，并且您没有连接表的模型，连接的每一侧只有 2 列。没有 ID 或时间戳。

has_many :through 用于当你想要一个多对多连接时，连接表有一个模型，使其实际上是一个双多对一连接，连接表有一个 id 列，时间戳，以及两个外键。

此外，从您的代码外观来看，您对 AdminUser 和 Project 做同样的事情，如果有一个 AdminUserProject 模型加入这两个模型，请使用 has_many :through not HABTM。

Answer 2

解决了这个问题。首先控制台没有重启。

其次，在 Rails 3.2 中，

belongs_to :admin_user, :class_name => "AdminUser" :foreign_key => 'admin_user_id'

应该是

belongs_to :admin_user, class_name: "AdminUser", foreign_key: 'admin_user_id'