ActiveModel::Validations#erros
errors
バリデーションが失敗したときに errors オブジェクトが作られる
code:ruby
class Book < ApplicationRecord
validates :name, presence: true
end
code:ruby
book = Book.new(name: '')
book.valid?
# => false
code:ruby
book.errors
book.errors.messages
book.errors.full_messages