Custom validation method to validate correct image types

model.rb

has_one_attached :image

validate :image_type

private

def image_type
   if image.attached? == false
     errors.add(:image, "is missing!")
   end
   if !image.content_type.in?(%('image/jpeg image/png'))
     errors.add(:image, "needs to be a jpeg or png!")
   end
end