1 files changed, 13 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/errors.rb b/activemodel/lib/active_model/errors.rb
index 963e52bff3..b713e99e25 100644
--- a/activemodel/lib/active_model/errors.rb
+++ b/activemodel/lib/active_model/errors.rb
@@ -328,6 +328,19 @@ module ActiveModel
       end
     end
 
+    # Will add an error message to each of the attributes in +attributes+ that
+    # is present (using Object#present?).
+    #
+    #   person.errors.add_on_present(:name)
+    #   person.errors.messages
+    #   # => { :name => ["must be blank"] }
+    def add_on_present(attributes, options = {})
+      Array(attributes).flatten.each do |attribute|
+        value = @base.send(:read_attribute_for_validation, attribute)
+        add(attribute, :not_blank, options) if value.present?
+      end
+    end
+
     # Returns +true+ if an error on the attribute with the given message is
     # present, +false+ otherwise. +message+ is treated the same as for +add+.
     #