Add `validates_attachment` method to model

lib/paperclip/validators.rb

@@ -11,5 +11,35 @@ module Paperclip
       extend  HelperMethods
       include HelperMethods
     end
+
+    module ClassMethods
+      # This method is a shortcut to validator classes that is in
+      # "Attachment...Validator" format. It is almost the same thing as the
+      # +validates+ method that shipped with Rails, but this is customized to
+      # be using with attachment validators. This is helpful when you're using
+      # multiple attachment validators on a single attachment.
+      #
+      # Example of using the validator:
+      #
+      #   validates_attachment :avatar, :presence => true,
+      #      :content_type => { :content_type => "image/jpg" },
+      #      :size => { :in => 0..10.kilobytes }
+      #
+      def validates_attachment(*attributes)
+        options = attributes.extract_options!.dup
+
+        Paperclip::Validators.constants.each do |constant|
+          if constant.to_s =~ /^Attachment(.+)Validator$/
+            validator_kind = $1.underscore.to_sym
+
+            if options.has_key?(validator_kind)
+              options[:"attachment_#{validator_kind}"] = options.delete(validator_kind)
+            end
+          end
+        end
+
+        validates(*attributes + [options])
+      end
+    end
   end
 end

test/validators_test.rb

+require './test/helper'
+
+class ValidatorsTest < Test::Unit::TestCase
+  def setup
+    rebuild_model
+  end
+
+  context "using the helper" do
+    setup do
+      Dummy.validates_attachment :avatar, :presence => true, :content_type => { :content_type => "image/jpg" }, :size => { :in => 0..10.kilobytes }
+    end
+
+    should "add the attachment_presence validator to the class" do
+      assert Dummy.validators_on(:avatar).any?{ |validator| validator.kind == :attachment_presence }
+    end
+
+    should "add the attachment_content_type validator to the class" do
+      assert Dummy.validators_on(:avatar).any?{ |validator| validator.kind == :attachment_content_type }
+    end
+
+    should "add the attachment_size validator to the class" do
+      assert Dummy.validators_on(:avatar).any?{ |validator| validator.kind == :attachment_size }
+    end
+  end
+end