Question

产品有许多产品图片，产品图片属于产品。这是架构

class ExempleController extends Controller {
        private $exemple;
        public function __construct(ExempleRepositoryInterface $home) {
            $this->exemple = $exemple;
        }
        public function test() {
            $data = $this->exemple->getquery(); / you can pass a variable here if you want like this $this->exemple->getquery('variable');

            // do stuff
        }

以下是模型

create_table "product_images", force: :cascade do |t|
    t.string   "image"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
  end

  create_table "products", force: :cascade do |t|
    t.string   "name"
    t.integer  "price"
    t.boolean  "availability"
    t.text     "about"
    t.integer  "ref"
    t.string   "texture"
    t.string   "dimensions"
    t.string   "shipping"
    t.string   "category"
    t.string   "notes"
    t.datetime "created_at",                null: false
    t.datetime "updated_at",                null: false
    t.string   "sizes",        default: [],              array: true
  end

我正在尝试添加迁移，将product_id作为product_images表的外键引用

class ProductImage < ActiveRecord::Base
    belongs_to :product
end

class Product < ActiveRecord::Base

    has_many :product_images

end

这是错误

class AddForeignKeyToProductImages < ActiveRecord::Migration
  def change
    add_foreign_key :product_images, :products, column: :product_id
  end
end

Answer 1

应该有效：

rails g migration AddProductToProductImages

class AddProductToProductImages < ActiveRecord::Migration
  def change
    add_column :product_images, :product_id, :integer
    add_foreign_key :product_images, :products
  end
end

您还可以执行以下操作：

rails g migration AddProductRefToProductImages product:references

class AddProductToProductImages < ActiveRecord::Migration
  def change
    add_reference :product_images, :product, index: true, foreign_key: true
  end
end

您可以查看API了解详情。

Answer 2

删除“AddForeignKeyToProductImages”迁移文件。然后...

在控制台中运行此命令：

rails g migration AddProductToProductImages product:references

应该生成以下迁移。

class AddProductToProductImages < ActiveRecord::Migration
  def change
    add_reference :product_images, :product, index: true
  end
end

然后运行bundle exec rake db:migrate

外键contstraint中引用的product_id不存在

2 个答案: