Rails 사용자 지정 유효성 검사 컨텍스트

class Post < ApplicationRecord
 validates :body, presence: true
 validates :title, uniqueness: true, on: :create 
 validates :published, exclusion: [nil], on: :update 
end

class Post < ApplicationRecord
 validates :title, presence: true 
 validates :published_at, presence: true, on: :publish
end

post = Post.new(title: "Rails validations")
post.valid? # true 
post.valid?(context: :publish) # false 
post.save(context: :publish) # false