mysql - ActiveRecord 关联 : am I doing it right?

Question

我正在构建一个简单的 Rails 应用程序(这是我的第一个 Rails 项目)，用于跟踪组内用户的统计信息。我已经使用迁移脚本创建了表，当我在 MySql 中查看时，一切看起来都正常，但当我将它们连接到另一个表时，并非所有模型都返回数据。

有人发现我的模型、迁移脚本或数据模型有什么问题吗？

这是我的迁移文件脚本代码:

class CreateGroupsUsers < ActiveRecord::Migration
  def change

    create_table :types do |t|
      t.string :name
    end

    create_table :groups do |t|
      t.string :name
      t.belongs_to :type, index: true
    end

    create_table :users do |t|
      t.string :username
      t.string :email
      t.string :first_name
      t.string :last_name
      t.string :e_password
      t.string :salt
      t.timestamps
    end

    create_table :roles do |t|
      t.string :name
    end

    create_table :groups_users, id: false do |t|
      t.belongs_to :group, index: true
      t.belongs_to :user, index: true
      t.belongs_to :role, index: true
    end

    create_table :statistics do |t|
      t.string :name
    end

    create_table :groups_users_statistics, id: false do |t|
      t.string :value
      t.belongs_to :group, index: true
      t.belongs_to :user, index: true
      t.belongs_to :statistic, index: true
    end

  end
end

这是我的模型:

class Type < ActiveRecord::Base
    has_many :groups
end

class Role < ActiveRecord::Base
    has_many :groups_users
end

class User < ActiveRecord::Base
    has_and_belongs_to_many :groups
    has_one :roles, through: :groups_users
end

class Group < ActiveRecord::Base
    has_and_belongs_to_many :users
    has_one :types
end

class Statistic < ActiveRecord::Base
    //i'm not too sure how to define this model
end

这是我的数据模型

Answer 1

我根据 Esse、Pavan 和 AndyV 的评论更新了我的模型。现在一切似乎都运行良好

class Type < ActiveRecord::Base
    has_many :groups
end

class Role < ActiveRecord::Base
    has_many :group_users
end

class User < ActiveRecord::Base
    has_many :group_users
    has_many :groups, through: :group_users

    has_many :group_user_statistics
    has_many :groups, through: :group_user_statistics
    has_many :statistics, through: :group_user_statistics
end

class Group < ActiveRecord::Base
    has_many :group_users
    has_many :users, through: :group_users

    has_many :group_user_statistics
    has_many :users, through: :group_user_statistics
    has_many :statistics, through: :group_user_statistics
end

class GroupUser < ActiveRecord::Base
    belongs_to :group
    belongs_to :user
end

class Statistic < ActiveRecord::Base
    has_many :group_user_statistics
    has_many :groups, through: :group_user_statistics
    has_many :users, through: :group_user_statistics
end

class GroupUserStatistic < ActiveRecord::Base
    belongs_to :user
    belongs_to :group
    belongs_to :statistic
end