Inherit key coercions.

CHANGELOG.md

@@ -4,6 +4,7 @@
 * [#249](https://github.com/intridea/hashie/pull/249): SafeAssignment will now also protect hash-style assignments - [@jrochkind](https://github.com/jrochkind).
 * [#251](https://github.com/intridea/hashie/pull/251): Add block to indifferent access #fetch - [@jgraichen](https://github.com/jgraichen).
 * [#252](https://github.com/intridia/hashie/pull/252): Add support for conditionally required Hashie::Dash attributes - [@ccashwell](https://github.com/ccashwell).
+* [#256](https://github.com/intridia/hashie/pull/256): Inherit key coercions - [@Erol](https://github.com/Erol).
 * Your contribution here.
 
 ## 3.3.2 (11/26/2014)

lib/hashie/extensions/coercion.rb

@@ -86,6 +86,9 @@ def replace(other_hash)
       end
 
       module ClassMethods
+        attr_writer :key_coercions
+        protected :key_coercions=
+
         # Set up a coercion rule such that any time the specified
         # key is set it will be coerced into the specified class.
         # Coercion will occur by first attempting to call Class.coerce
@@ -101,16 +104,15 @@ module ClassMethods
         #     coerce_key :user, User
         #   end
         def coerce_key(*attrs)
-          @key_coercions ||= {}
           into = attrs.pop
-          attrs.each { |key| @key_coercions[key] = into }
+          attrs.each { |key| key_coercions[key] = into }
         end
 
         alias_method :coerce_keys, :coerce_key
 
         # Returns a hash of any existing key coercions.
         def key_coercions
-          @key_coercions || {}
+          @key_coercions ||= {}
         end
 
         # Returns the specific key coercion for the specified key,
@@ -172,6 +174,12 @@ def value_coercion(value)
           from = value.class
           strict_value_coercions[from] || lenient_value_coercions[from]
         end
+
+        def inherited(klass)
+          super
+
+          klass.key_coercions = key_coercions
+        end
       end
     end
   end

spec/hashie/extensions/coercion_spec.rb

@@ -404,6 +404,21 @@ class TweetHash < MyHash
         expect(tweet[:user]).to be_a(UserHash)
       end
     end
+
+    context 'when subclassing' do
+      class MyHash < Hash
+        include Hashie::Extensions::Coercion
+
+        coerce_key :value, Integer
+      end
+
+      class MySubclass < MyHash
+      end
+
+      it 'inherits key coercions' do
+        expect(MyHash.key_coercions).to eql(MySubclass.key_coercions)
+      end
+    end
   end
 
   describe '#coerce_value' do