NoMethodError：未定義的方法'用戶'has_many：通過協會

Question

我試圖創建一個has_many：通過我的rails應用程序中的關聯，但是當我在rails控制檯中執行以下操作時出現錯誤。

2.0.0-p481 :001 > @group = Group.first 
Group Load (0.2ms) SELECT "groups".* FROM "groups" ORDER BY "groups"."id" ASC LIMIT 1 
=> #<Group id: 1, name: "First Group", description: "Woo", created_at: "2015-02-06 22:19:47", updated_at: "2015-02-06 22:19:47"> 
2.0.0-p481 :002 > @group.user 

NoMethodError: undefined method `user' for #<Group:0x00000004d53eb0> 
from /home/jon/.rvm/gems/ruby-2.0.0-p481/gems/activemodel-4.0.2/lib/active_model/attribute_methods.rb:439:in `method_missing' 
from /home/jon/.rvm/gems/ruby-2.0.0-p481/gems/activerecord-4.0.2/lib/active_record/attribute_methods.rb:155:in `method_missing' 
from (irb):2 
from /home/jon/.rvm/gems/ruby-2.0.0-p481/gems/railties-4.0.2/lib/rails/commands/console.rb:90:in `start' 
from /home/jon/.rvm/gems/ruby-2.0.0-p481/gems/railties-4.0.2/lib/rails/commands/console.rb:9:in `start' 
from /home/jon/.rvm/gems/ruby-2.0.0-p481/gems/railties-4.0.2/lib/rails/commands.rb:62:in `<top (required)>' 
from bin/rails:4:in `require' 
from bin/rails:4:in `<main>' 

我的模型：

用戶：

class User < ActiveRecord::Base 
    # Include default devise modules. Others available are: 
    # :confirmable, :lockable, :timeoutable and :omniauthable 
    before_create :do_mailchimp 

    devise :database_authenticatable, :registerable, 
     :recoverable, :rememberable, :trackable, :validatable 

    has_many :memberships 
    has_many :groups, through: :memberships 


    def do_mailchimp 
     gb = Gibbon::API.new("API") 
     gb.lists.subscribe({:id => 'ID', 
     :email => {:email => self.email },:double_optin => false}) 
    end 

end 

組：

class Group < ActiveRecord::Base 

    has_many :memberships 
    has_many :users, through: :memberships 

end 

成員：

class Membership < ActiveRecord::Base 

    belongs_to :user 
    belongs_to :group 

end 

我的遷移：

DeviseCreateUsers：

class DeviseCreateUsers < ActiveRecord::Migration 
    def change 
    create_table(:users) do |t| 
     ## Database authenticatable 
     t.string :email,    null: false, default: "" 
     t.string :encrypted_password, null: false, default: "" 

     ## Recoverable 
     t.string :reset_password_token 
     t.datetime :reset_password_sent_at 

     ## Rememberable 
     t.datetime :remember_created_at 

     ## Trackable 
     t.integer :sign_in_count, default: 0, null: false 
     t.datetime :current_sign_in_at 
     t.datetime :last_sign_in_at 
     t.string :current_sign_in_ip 
     t.string :last_sign_in_ip 

     ## Confirmable 
     # t.string :confirmation_token 
     # t.datetime :confirmed_at 
     # t.datetime :confirmation_sent_at 
     # t.string :unconfirmed_email # Only if using reconfirmable 

     ## Lockable 
     # t.integer :failed_attempts, default: 0, null: false # Only if lock strategy is :failed_attempts 
     # t.string :unlock_token # Only if unlock strategy is :email or :both 
     # t.datetime :locked_at 


     t.timestamps 
    end 

    add_index :users, :email,    unique: true 
    add_index :users, :reset_password_token, unique: true 
    # add_index :users, :confirmation_token, unique: true 
    # add_index :users, :unlock_token,   unique: true 
    end 
end 

CreateGroups：

class CreateGroups < ActiveRecord::Migration 
    def change 
    create_table :groups do |t| 
     t.string :name 
     t.string :description 

     t.timestamps 
    end 
    end 
end 

CreateMemberships：

class CreateMemberships < ActiveRecord::Migration 
    def change 
    create_table :memberships do |t| 

     t.timestamps 
    end 
    end 
end 

AddUserAndGroupIdToMembers臀部：

class AddUserAndGroupIdToMemberships < ActiveRecord::Migration 
    def change 
    add_column :memberships, :user_id, :integer 
    add_index :memberships, :user_id 
    add_column :memberships, :group_id, :integer 
    add_index :memberships, :group_id 
    end 
end 

我的架構：

ActiveRecord::Schema.define(version: 20150206225251) do 

    create_table "groups", force: true do |t| 
    t.string "name" 
    t.string "description" 
    t.datetime "created_at" 
    t.datetime "updated_at" 
    end 

    create_table "memberships", force: true do |t| 
    t.datetime "created_at" 
    t.datetime "updated_at" 
    t.integer "user_id" 
    t.integer "group_id" 
    end 

    add_index "memberships", ["group_id"], name: "index_memberships_on_group_id" 
    add_index "memberships", ["user_id"], name: "index_memberships_on_user_id" 

    create_table "users", force: true do |t| 
    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, null: false 
    t.datetime "current_sign_in_at" 
    t.datetime "last_sign_in_at" 
    t.string "current_sign_in_ip" 
    t.string "last_sign_in_ip" 
    t.datetime "created_at" 
    t.datetime "updated_at" 
    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 

end 

謝謝你的時間希望你能有所幫助。

Answer 1

您定義了一個Group has_many :users。因此，一組不具有user方法，而是一種users方法：

當然

@group = Group.first 

@group.users   #=> returns an array with all users in the first group 
@group.users.first #=> returns the first user in the first group