Rails 6 added new method of_kind? on ActiveModel::Errors

of_kind_method.rb

# Rails 6
class User < ApplicationRecord
  validates :name, presence: true
end

> user = User.new
=> #<User id: nil, name: nil, email: nil, rating: 0, password: nil, created_at: nil, updated_at: nil>

> user.valid?
=> false

> user.errors
=> #<ActiveModel::Errors:0x00007fc462a1d140 @base=#<User id: nil, name: nil, email: nil, rating: 0, password: nil, created_at: nil, updated_at: nil>, @messages={:name=>["can't be blank"]}, @details={:name=>[{:error=>:blank}]}>

> user.errors.of_kind?(:name)
=> false

> user.errors.of_kind?(:name, :blank)
=> true

> user.errors.of_kind?(:name, "can't be blank")
=> true

> user.errors.of_kind?(:name, "is blank")
=> false