Mastering Rails Validations: Contexts

validaation.rb

# http://blog.arkency.com/2014/04/mastering-rails-validations-contexts/
# http://blog.arkency.com/2014/05/mastering-rails-validations-objectify/

# The idea was, that it should not be possible to delete user who already took part of some important business activity.
class User < ActiveRecord::Base
  has_many :invoices
  validate :does_not_have_any_invoice, on: :destroy

  def destroy
    transaction do
      valid?(:destroy) or raise RecordInvalid.new(self)
      super()
    end
  end

  private

  def does_not_have_any_invoice
    errors.add(:invoices, :present) if invoices.exists?
  end
end

# allow us use two different kind context.
class Admin::UsersController
  def edit
    User.transaction do
      @user = User.find(params[:id])
      if @user.valid?(:admin) && @user.valid?(:create)
        @user.save!(validate: false)
        redirect # ...
      else
        render # ...
      end
    end
  end
end