mysql - Ruby on Rails 中跨 4 个模型的关系

Question

我正在尝试在我的 RoR 模型中建立一些高级关系。

到目前为止，我所做的工作是项目和任务 - 项目有任务，用户有项目。

我现在希望“注册”项目的用户现在可以“注册”该项目中的任务。

我目前的类(class)简介:

class AdminUser < ActiveRecord::Base
 has_and_belongs_to_many :projects
 has_and_belongs_to_many  :tasks
 has_many :admin_users_projects

[...]


class AdminUsersProject < ActiveRecord::Base

  belongs_to :admin_user
  has_and_belongs_to_many :project
  has_many :tasks

[...]

class Project < ActiveRecord::Base

  has_many :tasks
  has_and_belongs_to_many :admin_users
  has_and_belongs_to_many :admin_users_projects

[...]

class Task < ActiveRecord::Base

  belongs_to :project
  has_and_belongs_to_many :admin_users
  belongs_to :admin_users_project

[...]

架构如下所示:

 create_table "admin_users", :force => true do |t|
    t.string   "first_name",      :limit => 25
    t.string   "last_name",       :limit => 50
    t.string   "email",           :limit => 100, :default => "", :null => false
    t.string   "hashed_password", :limit => 40
    t.datetime "created_at",                                     :null => false
    t.datetime "updated_at",                                     :null => false
    t.string   "username",        :limit => 25
    t.string   "salt",            :limit => 40
  end

  add_index "admin_users", ["username"], :name => "index_admin_users_on_username"

  create_table "admin_users_projects", :force => true do |t|
    t.integer "admin_user_id"
    t.integer "project_id"
  end

  add_index "admin_users_projects", ["admin_user_id", "project_id"], :name =>     "index_admin_users_projects_on_admin_user_id_and_project_id"

  create_table "projects", :force => true do |t|
    t.string   "name"
    t.integer  "position"
    t.boolean  "visible",    :default => false
    t.datetime "created_at",                    :null => false
    t.datetime "updated_at",                    :null => false
  end

  create_table "tasks", :force => true do |t|
    t.integer  "project_id"
    t.string   "permalink"
    t.integer  "position"
    t.boolean  "visible"
    t.datetime "created_at",    :null => false
    t.datetime "updated_at",    :null => false
    t.string   "name"
    t.integer  "admin_user_id"
    t.integer  "progress"
  end

  add_index "tasks", ["permalink"], :name => "index_tasks_on_permalink"
  add_index "tasks", ["project_id"], :name => "index_tasks_on_project_id"

end

我有显示项目的 View ，然后是其任务子集的 View 我还有一个显示用户项目的 View ，但现在我希望它显示用户任务的子集。

我对“admin_user_projects”的简要看法如下:

    <% @admin_users_projects.each do |admin_users_projects| %>
    <tr>
        <td><%= admin_users_projects.admin_user_id %></td>
        <td><%= admin_users_projects.admin_user.username  %></td>
        <td><%= admin_users_projects.project_id %></td>
        <td><%= admin_users_projects.project.name  %></td>
    </tr>
    <% end %>

这显示了用户 ID、用户名、项目 ID 和项目名称。我现在想添加一行，显示用户“注册”该项目的任务数量。我已经尝试过了

        <td><%= admin_users_projects.tasks.size  %></td>

但得到以下内容:

Mysql2::Error: Unknown column 'tasks.admin_users_project_id' in 'where clause': SELECT COUNT(*) FROM `tasks`  WHERE `tasks`.`admin_users_project_id` = 1

有人知道如何让这些关系有效运作吗？

Answer 1

我的建议是这样的:

class AdminUser < ActiveRecord::Base
  has_and_belongs_to_many :projects
  has_many :assigned_tasks
  has_many :tasks, through: :assigned_tasks
end

class AssignedTask < ActiveRecord::Base
  belongs_to :user
  belongs_to :task

  validate :user_assigned_to_project

  private

  def user_assigned_to_project
    unless user.projects.include? task.project
      errors.add(:project, "is not valid")
    end
  end
end

class Project < ActiveRecord::Base
  has_and_belongs_to_many :admin_users
  has_many :tasks
end

class Task < ActiveRecord::Base
  has_many :assigned_tasks
  has_many :users, through: :assigned_tasks
  belongs_to :project
end


class GiantMigration < ActiveRecord::Migration
  create_table :admin_users do |t|
    # whatever
  end
  create_table :projects do |t|
    # whatever
  end
  create_table :assigned_tasks do |t|
    t.integer :admin_user_id, null: false
    t.integer :task_id, null: false
  end
  create_table :tasks do |t|
    # whatever
    t.integer :project_id
  end
  create_table :admin_users_projects, id: false do |t|
    t.integer :admin_user_id, null: false
    t.integer :project_id, null: false
  end
end

一些一般注意事项:

• 您必须选择是要使用纯联接表 (HABTM) 还是联接模型 (has_many :through)。现在你正在混合两者。
• 请勿在迁移中默认使用 force: true。
• 遵守 Rails 的约定:has_and_belongs_to_many :projects(您使用了单数项目)