Partially validate model attributes. Good for multi-step wizards form without saving record on each step.

partially_valid.rb

module PartiallyValidatable
  extend ActiveSupport::Concern

  included do
    def self.partially_valid?(params, valid=true)
      mock = self.new(params)
      params.each{|attr, _| valid = false if mock.errors.messages[attr.to_sym].present?} unless mock.valid?
      valid
    end

    def self.generate_errors(params, errors=[])
      mock = self.new(params)
      params.each{|attr, _| errors << mock.errors.messages[attr.to_sym] if mock.errors.messages[attr.to_sym].present?} unless mock.valid?
      errors.flatten
    end
  end

end