如何让has_many工作？

Question

型号：

class Game < ActiveRecord::Base
  belongs_to :manufacturer
end

class Manufacturer < ActiveRecord::Base
    has_many :games
end

迁移：

class CreateManufacturers < ActiveRecord::Migration
  def change
    create_table :manufacturers do |t|
      t.string :name

      t.timestamps null: false
    end
  end
end

class CreateGames < ActiveRecord::Migration
  def change
    create_table :games do |t|
      t.string :name
      t.references :manufacturer, index: true, foreign_key: true

      t.timestamps null: false
    end
  end
end

当我输入m = Game.find(2).manufacturer时，这有效，并给我制造商名称。但是当我给g = Manufacturer.find(1).games控制台抛出许多错误时。为什么has_many不起作用？

或

如何获得第一家制造商开发的所有游戏？

显示错误：

NoMethodError: undefined method `games' for #<Manufacturer:0x007f996dc75368>