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是收到错误，我的类如下，并且当我使用时发生错误，task.admin_users_tasks

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语法并提供了一个模型，您应该使用has_many：through。我会以不同的方式设置模型，然后rails可能会稍微混淆一点。

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用于何时需要多次连接，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：通过是为了你想要一个多人连接，并且有一个连接表的模型，使它实际上是一个双多连接，并且连接表有一个id列，时间戳，以及两个外键。

同样通过代码的外观，您可以使用AdminUser和Project执行相同操作，如果有一个AdminUserProject模型加入这两个模型，请使用has_many：通过非HABTM。

Answer 2

修正了问题。首先，控制台尚未重启。

其次在rails 3.2中是什么，

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'

Ruby on Rails 3个模型之间的关系

2 个答案: