Ruby on Mac OS X Leopard with DTrace, XCode and Interface Builder support

Posted by Werner Schuster on Oct 26, 2007

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Apple

The long awaited Mac OS X Leopard is released today, and it ships with support for Ruby development - quite extensive support. The MacOS forge Wiki lists the new Ruby features of Leopard. 

Ruby itself was upgraded to 1.8.6 p36, which was the latest stable release that we could grab. We additionally merged patches for important bugs that were discovered after p36, but could not be part of an official Ruby patch release at that time (they actually were, but after our deadline).
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The Ruby libruby.1.dylib library, which contains the core of the interpreter, is available as a 4-way fat universal binary, for the ppc, i386, ppc64 and x86_64 architectures. You can therefore embed Ruby in a 64-bit application. All C extensions are also available for both 32-bit and 64-bit architectures, except Tk which cannot go 64-bit. The Ruby interpreter launcher, /usr/bin/ruby, was therefore left 32-bit only to not break scripts that use the Tk extension, or any other 32-bit only dependency.
Ruby C extensions will by default compile 2-way fat, for ppc and i386. You can set the ARCHFLAGS environment variable to configure the build of an extension, if for example it links against a non-universal library (like the mysql.com binaries which are delivered per processor architecture).

Next to all these details, an interesting addition to the Ruby interpreter is support for DTrace static probes. DTrace was originally developed by Sun for Solaris, but is now being ported to other Unix versions as well. It allows to do low-overhead tracing and profiling of applications and even Operating System code. The Mac OS X Ruby interpreter includes these probes:

Probes

The probes that are currently in Ruby-DTrace

Probe name	Description
function-entry	Probe that fires when a Ruby method is entered
function-return	Probe that fires when a Ruby method returns
raise	Probe that fires when a Ruby exception is raised
rescue	Probe that fires when a Ruby exception is rescued
line	Probe that fires for every line of Ruby executed
gc-begin	Probe that fires right before a GC cycle begins
gc-end	Probe that fires right after a GC cycle finishes
object-create-start	Probe that fires directly before a Ruby object is allocated
object-create-done	Probe that fires when Ruby is finished allocating an object
object-free	Probe that fires every time a Ruby object is freed
ruby-probe	Probe that can be fired from Ruby code (see below)

These were ported from Joyents Ruby DTrace project. Mac OS X Leopard also includes a tool called Instrument, which allows to visualize tracing and profiling events.

Apple also included Ruby support for XCode and the GUI Builder Interface Builder:

Xcode in Leopard comes with the RubyCocoa project templates, but also with a template to generate a Test/Unit target. Xcode also supports better Ruby auto-completion, driven by the BridgeSupport mechanism.
Interface Builder now officially supports Ruby. For example, you can write a Ruby class in Xcode, with outlets and/or actions, and everything will automatically appears in IB. IB uses RubyCocoa's rb_nibtool utility to synchronize the metadata. On the other way, you can manually define outlets and/or actions in IB, drag-and-drop them in an Xcode Ruby file, and the corresponding Ruby code will be pasted in it.

Mac OS X Leopard also includes a new framework called Scripting Bridge which allows to script applications. Ruby is also supported:

ScriptingBridge is a new Leopard framework that provides access to the AppleEvent infrastructure, on which AppleScript is based. ScriptingBridge will dynamically generate an Objective-C interface that corresponds to the scriptable dictionary of a given application. You can then send messages and control this application from Objective-C.
Thanks to RubyCocoa, it is also possible to use ScriptingBridge from Ruby. Some scripting elements are not yet accessible though, like enumerations, but most of the functionality should be available.