ruby-on-rails - has_many:通过未初始化的常量

我已经阅读了有关has_many的文档和大量教程：通过Rails中的关系，但是我一生无法理解它。

我正在尝试向我的current_user（devise）添加一个组，并且在Group和User之间有一个带有状态的表（该组的用户状态是可变的）。

现在，每当我创建一个新组时，都会出现一条错误消息，提示uninitialized constant Group::GroupUser

这是我的模特：

groupuser.rb

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

group.rb

class Group < ActiveRecord::Base
    has_many                            :clients
    has_and_belongs_to_many             :pictograms

    has_many :group_users
    has_many :users, :through => :group_users

    accepts_nested_attributes_for :clients

    validates_length_of                 :name,  :minimum => 5
    validates_presence_of               :name
    validates_presence_of               :background
    validates_presence_of               :clocktype
end

User.rb

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :token_authenticatable, :confirmable,
  # :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable


  validates_presence_of   :first_name
  validates_presence_of   :last_name
  validates               :email, presence: true, uniqueness: true

  has_many :group_users
  has_many :groups, :through => :group_users

  has_attached_file :avatar, :styles => {
                                :medium => "300x300#",
                                :thumb => "100x100#"
                             }
  validates_attachment_content_type :avatar, :content_type => ['image/jpg', 'image/png', 'image/jpeg']

  validates_attachment :avatar,
                  :size => { :in => 0..1.megabytes }

  def completeName
    "#{self.first_name} #{self.last_name}"
  end
end

以及来自schema.rb的相关内容

  create_table "group_users", id: false, force: true do |t|
    t.integer "group_id"
    t.integer "user_id"
    t.integer "status",   default: 0
  end

  add_index "group_users", ["group_id"], name: "index_group_users_on_group_id"
  add_index "group_users", ["user_id"], name: "index_group_users_on_user_id"

  create_table "groups", force: true do |t|
    t.string   "name"
    t.integer  "clocktype"
    t.string   "background"
    t.datetime "created_at"
    t.datetime "updated_at"
  end
  create_table "users", force: true do |t|
    t.string   "first_name"
    t.string   "last_name"
    t.string   "password"
    t.string   "avatar_file_name"
    t.string   "avatar_content_type"
    t.integer  "avatar_file_size"
    t.datetime "avatar_updated_at"
    t.datetime "created_at"
    t.datetime "updated_at"
    t.string   "email",                  default: "", null: false
    t.string   "encrypted_password",     default: "", null: false
    t.string   "reset_password_token"
    t.datetime "reset_password_sent_at"
    t.datetime "remember_created_at"
    t.integer  "sign_in_count",          default: 0
    t.datetime "current_sign_in_at"
    t.datetime "last_sign_in_at"
    t.string   "current_sign_in_ip"
    t.string   "last_sign_in_ip"
  end

  add_index "users", ["email"], name: "index_users_on_email", unique: true
  add_index "users", ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true

最后。引发错误的行

@group.users << current_user

最佳答案

我看到的问题是您对GroupUser的命名

我们一直使用联接模型，并用下划线命名它们：

group_user.rb
class GroupUser < ActiveRecord::Base
  belongs_to :group
  belongs_to :user
end

未初始化的常量错误将由模型未正确加载引起，我认为这是由于命名问题引起的。如果这不起作用，则应在关系声明中使用:class_name参数引用模型：

  has_many :group_users, :class_name => 'GroupUser'
  has_many :groups, :through => :group_users

更新资料

We wanted to call extra attributes从加入模型中，发现这种方式：

#app/models/message.rb
has_many :image_messages, :class_name => 'ImageMessage'
has_many :images, -> { select("#{Image.table_name}.*, #{ImageMessage.table_name}.caption AS caption") }, :class_name => 'Image', :through => :image_messages, dependent: :destroy

它使用创建ActiveRecord关联时可以使用的select方法，正如我们discovered from this RailsCast一样，您可以使用该方法在查询中创建alias列

对于您来说，您不妨尝试一下：

#app/models/user.rb
has_many :group_users, :class_name => 'Groupuser'
has_many :groups, -> { select("#{User.table_name}.*, #{Groupuser.table_name}.status AS status") }, :class_name => 'Group', :through => :group_users, dependent: :destroy