1 files changed, 115 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/validations/callbacks.rb b/activemodel/lib/active_model/validations/callbacks.rb
new file mode 100644
index 0000000000..edfffdd3ce
--- /dev/null
+++ b/activemodel/lib/active_model/validations/callbacks.rb
@@ -0,0 +1,115 @@
+module ActiveModel
+  module Validations
+    # == Active \Model \Validation \Callbacks
+    #
+    # Provides an interface for any class to have +before_validation+ and
+    # +after_validation+ callbacks.
+    #
+    # First, include ActiveModel::Validations::Callbacks from the class you are
+    # creating:
+    #
+    #   class MyModel
+    #     include ActiveModel::Validations::Callbacks
+    #
+    #     before_validation :do_stuff_before_validation
+    #     after_validation  :do_stuff_after_validation
+    #   end
+    #
+    # Like other <tt>before_*</tt> callbacks if +before_validation+ returns
+    # +false+ then <tt>valid?</tt> will not be called.
+    module Callbacks
+      extend ActiveSupport::Concern
+
+      included do
+        include ActiveSupport::Callbacks
+        define_callbacks :validation,
+                         terminator: ->(_,result) { result == false },
+                         skip_after_callbacks_if_terminated: true,
+                         scope: [:kind, :name]
+      end
+
+      module ClassMethods
+        # Defines a callback that will get called right before validation
+        # happens.
+        #
+        #   class Person
+        #     include ActiveModel::Validations
+        #     include ActiveModel::Validations::Callbacks
+        #
+        #     attr_accessor :name
+        #
+        #     validates_length_of :name, maximum: 6
+        #
+        #     before_validation :remove_whitespaces
+        #
+        #     private
+        #
+        #     def remove_whitespaces
+        #       name.strip!
+        #     end
+        #   end
+        #
+        #   person = Person.new
+        #   person.name = '  bob  '
+        #   person.valid? # => true
+        #   person.name   # => "bob"
+        def before_validation(*args, &block)
+          options = args.last
+          if options.is_a?(Hash) && options[:on]
+            options[:if] = Array(options[:if])
+            options[:on] = Array(options[:on])
+            options[:if].unshift lambda { |o|
+              options[:on].include? o.validation_context
+            }
+          end
+          set_callback(:validation, :before, *args, &block)
+        end
+
+        # Defines a callback that will get called right after validation
+        # happens.
+        #
+        #   class Person
+        #     include ActiveModel::Validations
+        #     include ActiveModel::Validations::Callbacks
+        #
+        #     attr_accessor :name, :status
+        #
+        #     validates_presence_of :name
+        #
+        #     after_validation :set_status
+        #
+        #     private
+        #
+        #     def set_status
+        #       self.status = errors.empty?
+        #     end
+        #   end
+        #
+        #   person = Person.new
+        #   person.name = ''
+        #   person.valid? # => false
+        #   person.status # => false
+        #   person.name = 'bob'
+        #   person.valid? # => true
+        #   person.status # => true
+        def after_validation(*args, &block)
+          options = args.extract_options!
+          options[:prepend] = true
+          options[:if] = Array(options[:if])
+          if options[:on]
+            options[:on] = Array(options[:on])
+            options[:if].unshift("#{options[:on]}.include? self.validation_context")
+          end
+          set_callback(:validation, :after, *(args << options), &block)
+        end
+      end
+
+    protected
+
+      # Overwrite run validations to include callbacks.
+      def run_validations! #:nodoc:
+        run_callbacks(:validation) { super }
+      end
+    end
+  end
+end