验证图片存在时出错4

This is my Gig model

这是我的Gig模型

class Gig < ActiveRecord::Base
  has_attached_file :image, :styles => { :medium => "360x170>", :bigger => "650x459>" }
  validates_attachment_content_type :image, :content_type => /\Aimage\/.*\Z/
  validate :image_size_validation

  def image_size_validation
    if image.size > 2.megabytes
      errors.add(:base, "Image should be less than 2MB")
    end
  end
end
class Gig <