A simple, powerful Objective-C value transformation API extracted from RestKit.
RKValueTransformers is a standalone library that provides a simple value transformation API in Objective-C. Value transformation is the process of converting a value between representations and is a core part of any system that requires that data be transmitted and received in a serialization format distinct from the local data model.
In the general context of a RESTful API this means the transformation between values encoded in an XML or JSON document and local attributes of your data model. The most familiar and obvious example is the transformation of date and time data encoded as a string in a JSON document and represented locally as an NSDate attribute of an NSObject or NSManagedObject derived class. RKValueTransformers provides a simple, well-designed API for generalizing and simplifying the task of handling an arbitrarily complex set of value transformation requirements for your iOS or Mac OS X application.
SDK for Apple
Caching in RKCompoundValueTransformer for source/destination class pairs
Avoid creating errors unless necessary
Optimize the RKValueTransformerTestInputValueIsKindOfClass and RKValueTransformerTestOutputValueClassIsSubclassOfClass macros