Hashie::Trash transforms can be inherited.

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 * [#183](https://github.com/intridea/hashie/pull/183): Added Mash#load with YAML file support - [@gregory](https://github.com/gregory).
 * [#197](https://github.com/intridea/hashie/pull/197): Dont convert keys to string on initalization of mash - [@gregory](https://github.com/gregory).
+* [#201](https://github.com/intridea/hashie/pull/201): Hashie::Trash transforms can be inherited - [@fobocaster](https://github.com/fobocaster).
 * Your contribution here.
 
 ## 3.2.0 (7/10/2014)

lib/hashie/trash.rb

@@ -39,6 +39,16 @@ def self.property(property_name, options = {})
       end
     end
 
+    class << self
+      attr_reader :transforms
+    end
+    instance_variable_set('@transforms', {})
+
+    def self.inherited(klass)
+      super
+      klass.instance_variable_set('@transforms', transforms.dup)
+    end
+
     # Set a value on the Dash in a Hash-like way. Only works
     # on pre-existing properties.
     def []=(property, value)
@@ -69,10 +79,6 @@ def self.permitted_input_keys
 
     private
 
-    def self.properties
-      @properties ||= []
-    end
-
     def self.translations
       @translations ||= {}
     end
@@ -81,10 +87,6 @@ def self.inverse_translations
       @inverse_translations ||= Hash[translations.map(&:reverse)]
     end
 
-    def self.transforms
-      @transforms ||= {}
-    end
-
     # Raises an NoMethodError if the property doesn't exist
     #
     def property_exists?(property)

spec/hashie/trash_spec.rb

@@ -186,6 +186,28 @@ class TrashLambdaTest3 < Hashie::Trash
     end
   end
 
+  describe 'inheritable transforms' do
+    class TrashA < Hashie::Trash
+      property :some_value, transform_with: lambda { |v| v.to_i }
+    end
+
+    class TrashB < TrashA
+      property :some_other_value, transform_with: lambda { |v| v.to_i }
+    end
+
+    class TrashC < TrashB
+      property :some_value, transform_with: lambda { |v| -v.to_i }
+    end
+
+    it 'inherit properties transforms' do
+      expect(TrashB.new(some_value: '123', some_other_value: '456').some_value).to eq(123)
+    end
+
+    it 'replaces property transform' do
+      expect(TrashC.new(some_value: '123', some_other_value: '456').some_value).to eq(-123)
+    end
+  end
+
   it 'raises an error when :from have the same value as property' do
     expect do
       class WrongTrash < Hashie::Trash