JRSwizzle

Description

JRSwizzle is source code package that offers a single, easy, correct+consistent interface for exchanging Objective-C method implementations ("method swizzling") across many versions of Mac OS X, Objective-C and runtime architectures.

More succinctly: JRSwizzle wants to be your one-stop-shop for all your method swizzling needs.

Download

$ cd /path/to/top/of/your/project
$ git submodule add git://github.com/rentzsch/jrswizzle.git JRSwizzle
$ git submodule init && git submodule update

# OPTIONAL: Execute the following commands if you want to explicitly peg
# to a certain version. Otherwise `git submodule update` will keep you
# current with HEAD.

$ cd JRSwizzle
$ git checkout v1.0d1

Reasons for Existence

• Easy: Just do this: [SomeClass jr_swizzle:@selector(foo) withMethod:@selector(my_foo) error:&error]; Voila.
• Correct: There's a subtle interaction between method swizzling and method inheritance. Following in Kevin Ballard's footsteps, this package Does The Right Thing.
• Compatible: JRSwizzle should Just Work on any version of Mac OS X you care about. Here's the exhaustive compatibility list:
  • Mac OS X v10.3/ppc (Ballard implementation)
  • Mac OS X v10.4/ppc (Ballard implementation)
  • Mac OS X v10.4/i386 (Ballard implementation)
  • Mac OS X v10.5/ppc (method_exchangeImplementations+Ballard implementation)
  • Mac OS X v10.5/i386 (method_exchangeImplementations+Ballard implementation)
  • Mac OS X v10.5/ppc64 (method_exchangeImplementations+Ballard implementation)
  • Mac OS X v10.5/x86_64 (method_exchangeImplementations+Ballard implementation)
• Robust: All parameters are checked and JRSwizzle returns an optional NSError with high-quality diagnostics.

Support

Please use JRSwizzle's Lighthouse project site to file bugs or feature requests.

To contribute, please fork this project, make+commit your changes and then send me a pull request.

Comparison

There's at least four swizzling implementations floating around. Here's a comparison chart to help you make sense of how they relate to each other and why JRSwizzle exists.

• Classic is the canonical MethodSwizzle() implementation as described in CocoaDev's MethodSwizzling page.
• Ballard is Kevin Ballard's improved implementation which solves the inherited method problem.
• Apple is 10.5's new method_exchangeImplementations API.
• JRSwizzle is this package.

License

The source code is distributed under the nonviral MIT License. It's the simplest most permissive license available.

Version History

• v1.0d1: May 31 2009

  • [FIX] Soothe valgrind by nulling out hoisted_method_list->obsolete, which it apparently reads. (Daniel Jalkut)

  • [FIX] Xcode 3.2 apparently now needs ARCHS set explicitly for 10.3 targets. (rentzsch)

• v1.0d0: Apr 09 2009

  • Moved to github.

• v1.0d0: Dec 28 2007

  • Under development.