ActiveStorage File Attachment Validation

Question

Is there a way to validate attachments with ActiveStorage? For example, if I want to validate the content type or the file size?

Something like Paperclip\'s approach wou

Answer 1

I found a way to validate and delete attachments with callback before_save. This is a useful approach because if you validate file during the transaction (and you want to purge it), after adding error and it will rollback deleting the attachment.

before_save :check_logo_file, on: %i[create update]

def check_favicon_content_type
    PartnerValidators::CustomPartnerFaviconValidator.new.validate(self)
end

module PartnerValidators
    class CustomPartnerFaviconValidator < ActiveModel::Validator
        ALLOWED_MIME_TYPES = %w(image/vnd.microsoft.icon image/x-icon image/png).freeze
        private_constant :ALLOWED_MIME_TYPES

        def validate(partner)
            if partner.favicon.attached? && invalid_content_type?(partner)
                partner.errors.add(:favicon, I18n.t("active_admin.errors.favicon"))
                partner.favicon.purge
            end
        end

        private

        def invalid_content_type?(partner)
            !partner.favicon.blob.content_type.in?(ALLOWED_MIME_TYPES)
        end
    end
end