GitHub repository: kvokka/active_storage_validations
Description: Do it like => validates :photos, attached: true, content_type: ['image/png', 'image/jpg', 'image/jpeg'], size: { less_than: 500.kilobytes }, limit: { min: 1, max: 3 }, aspect_ratio: :landscape, dimension: { width: { in: 800..1600 }