Rails 6 adds ActiveModel::Errors#of_kind?

Rails 6 added of_kind? on ActiveModel::Errors. It returns true if the ActiveModel::Errors object has provided a key and message associated with it. The default message is :invalid.

of_kind? is same as ActiveModel::Errors#added? but, it doesn't take extra options as a parameter.

Let's checkout how it works.

Rails 6.0.0.beta2

>> class User < ApplicationRecord
>>   validates :name, presence: true
>> end

>> user = User.new

=> => #<User id: nil, name: nil, password: nil, created_at: nil, updated_at: nil>

>> user.valid?

=> false

>> user.errors

=> #<ActiveModel::Errors:0x00007fc462a1d140 @base=#<User id: nil, name: nil, 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

Here is the relevant pull request.