1 files changed, 64 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/validations/presence.rb b/activerecord/lib/active_record/validations/presence.rb
new file mode 100644
index 0000000000..056527b512
--- /dev/null
+++ b/activerecord/lib/active_record/validations/presence.rb
@@ -0,0 +1,64 @@
+module ActiveRecord
+  module Validations
+    class PresenceValidator < ActiveModel::Validations::PresenceValidator
+      def validate(record)
+        super
+        attributes.each do |attribute|
+          next unless record.class.reflect_on_association(attribute)
+          value = record.send(attribute)
+          if Array(value).all? { |r| r.marked_for_destruction? }
+            record.errors.add(attribute, :blank, options)
+          end
+        end
+      end
+    end
+
+    module ClassMethods
+      # Validates that the specified attributes are not blank (as defined by
+      # Object#blank?), and, if the attribute is an association, that the
+      # associated object is not marked for destruction. Happens by default
+      # on save.
+      #
+      #   class Person < ActiveRecord::Base
+      #     has_one :face
+      #     validates_presence_of :face
+      #   end
+      #
+      # The face attribute must be in the object and it cannot be blank or marked
+      # for destruction.
+      #
+      # If you want to validate the presence of a boolean field (where the real values
+      # are true and false), you will want to use
+      # <tt>validates_inclusion_of :field_name, :in => [true, false]</tt>.
+      #
+      # This is due to the way Object#blank? handles boolean values:
+      # <tt>false.blank? # => true</tt>.
+      #
+      # This validator defers to the ActiveModel validation for presence, adding the
+      # check to see that an associated object is not marked for destruction. This
+      # prevents the parent object from validating successfully and saving, which then
+      # deletes the associated object, thus putting the parent object into an invalid
+      # state.
+      #
+      # Configuration options:
+      # * <tt>:message</tt> - A custom error message (default is: "can't be blank").
+      # * <tt>:on</tt> - Specifies when this validation is active. Runs in all
+      #   validation contexts by default (+nil+), other options are <tt>:create</tt>
+      #   and <tt>:update</tt>.
+      # * <tt>:if</tt> - Specifies a method, proc or string to call to determine if
+      #   the validation should occur (e.g. <tt>:if => :allow_validation</tt>, or
+      #   <tt>:if => Proc.new { |user| user.signup_step > 2 }</tt>). The method, proc
+      #   or string should return or evaluate to a true or false value.
+      # * <tt>:unless</tt> - Specifies a method, proc or string to call to determine
+      #   if the validation should not occur (e.g. <tt>:unless => :skip_validation</tt>,
+      #   or <tt>:unless => Proc.new { |user| user.signup_step <= 2 }</tt>). The method,
+      #   proc or string should return or evaluate to a true or false value.
+      # * <tt>:strict</tt> - Specifies whether validation should be strict.
+      #   See <tt>ActiveModel::Validation#validates!</tt> for more information.
+      #
+      def validates_presence_of(*attr_names)
+        validates_with PresenceValidator, _merge_attributes(attr_names)
+      end
+    end
+  end
+end