FormObject

class User < ActiveRecord::Base
end

# attributes => {email: "test@example.com", name: "name"}

# For base auth
class BaseAuthForm < FormObject::Base
  map_model User, as: :base_auth
  attribute :email, String # => map form attribute to model attribute

  validates :email, presence: true # => validate email in form ONLY!
end

# For any other auth
class TwitterAuthForm < FormObject::Base
  map_model User      # name => twitter_auth (name will be generated 
                      # automatically from class name)
                      # There is nothing to validate
end

  @user = User.find(params[:id])
  @form = @user.form( :base_auth ) # This retrive BaseAuthForm instance
                                  # with attributes from model
  @form.assign_attributes(params[:user]) # assign attributes from hash

  if @form.valid?
    @form.persist_model           # TODO: maybe other method name?
  end