markdown 红宝石オブジェクトに加载ActiveModelの机能を追加する

Posted 2021-05-05

単純な属性とvalidationを持つオブジェクトを作る
```
class CustomModel
  include ActiveModel::Model
  include ActiveModel::Attributes

  attribute :name, :string, default: ''
  validates :name, presence: true
end
```