Why MacRuby Matters
Patrick Thomson
C4[3]
September 2009

Edsger Dijkstra

“Go To Statement Considered Harmful”

Dijkstraʼs Algorithm

“The effective exploitation of the
powers of abstraction must be
regarded as one of the most vital
activities of a computer
programmer.”

Objective-C

insufficiently powerful abstraction

What does Objective-C lack?

1. code reuse

inheritance alone
is not enough

singletons

inheritance

In Objective-C:
1. create a static, shared instance
2. initialize once and only once
3. add an sharedInstance accessor method
…for every singleton class.
Tedious.

tedium sucks

mixins

units of behavior;
mix-in common functionality
across unrelated classes

With mixins:
class Example
include Singleton
# your methods here
end

foo = Example.instance

not a new idea

Symbolics Lisp

1980

1. code reuse
2. safety

C is powerful.

C is powerful. (At the price of safety.)

We see Cʼs unsafeness throughout Objective-C.

raw pointers: bad news.

easily-confusable garbage collection

exceptions

creation, @try, and @throw are all expensive

Cocoa isnʼt exception-safe.

mishmash of NSError**,
NSException, and error codes

1. code reuse
2. safety
3. syntactic abstraction

[NSArray arrayWithObjects: @"a", @"b", @"c", nil];
vs.
["a", "b", "c"]

[NSDictionary dictionaryWithObjectsAndKeys:
@"Chicago", @"location", @"C4", @"event", nil];
vs.
{"location" => "Chicago", "event" => "C4"}

[foo compare:bar] == NSComparisonResultAscending
vs.
foo < bar

I want a language that lets
Cocoa shine.

MacRuby.

new Ruby implementation

+
powered by LLVM

+ +
on top of CoreFoundation

irb(main):001:0> "c4".class
=> NSMutableString
irb(main):002:0> [1, 2, 3].class
=> NSMutableArray
irb(main):003:0> {:tollfree => "bridging"}.class
=> NSMutableDictionary
irb(main):004:0> "/usr/local/bin".pathComponents
=> ["/", "usr", "local", "bin"]
Ruby objects Cocoa objects

irb(main):001:0> 3000.class
=> Fixnum
irb(main):002:0> 3000.is_a? NSNumber
=> true
irb(main):003:0> 3000.is_a? NSObject
=> true
irb(main):003:0> 3000.class.is_a? NSObject
=> true
Everything is an NSObject

Laurent Sansonetti
Vincent Isambart
Rich Kilmer
Eloy Duran
Ben Stiglitz
Matt Aimonetti

MacRuby isnʼt…

a bridge

MacRuby != RubyCocoa

a toy

provides real solutions to
real-world problems

example: threading

Global Interpreter Locks

only one system thread can touch
the interpreter at any given time

prevents true multithreading

MacRuby has no GIL!

So why should you, as Cocoa
developers, use MacRuby?

itʼs fast

historically slow

fib(40)

static int fib(int n)
{
if (n < 3) {
return 1;
} else {
return fib(n - 1) + fib(n - 2);
}
}

@implementation Fib
- (int)fib:(int)n
{
if (n < 3) {
return 1;
} else {
return [self fib:n - 1] + [self fib:n - 2];
}
}
@end

C Objective-C
4
3
execution time (s)
2
1
0
fib(40)

def fib(n)
if n < 3
1
else
fib(n-1) + fib(n-2)
end
end

C MacRuby Objective-C
4
3
execution time (s)
2
1
0
fib(40)

Faster than Objective-C‽

macruby --compile

first ahead-of-time compiler
for Ruby

itʼs beautiful

Objective-C:
[obj setValue:val forKey:key]

Bridges:
obj.setValue_forKey(val, key)
READABILITY FAIL

no_underscores_plz_k_thx

MacRuby:
obj.setValue(val, forKey:key)

HotCocoa

mapping Cocoa to idiomatic Ruby

[[NSImage alloc] initWithContentsOfFile:path];
becomes
image(:file => path)

[[NSGradient alloc]
initWithStartingColor: [NSColor greyColor]
endingColor: [NSColor blueColor]];
becomes
gradient(:start => color(:name => "grey"),
:end => color(:name => "blue"))

a real, robust macro system

itʼs conceptually sound

single inheritance
open classes
message-based object model
dynamically typed
garbage-collected

Objective-C is C with the Smalltalk
object model attached.
Ruby is Smalltalk with C syntax.

itʼs fully integrated with the
Cocoa toolchain

Yeah, We Got That

itʼs 100% compatible with every
Cocoa framework

BridgeSupport lets you call any
C-based API from MacRuby

CFStringGetLength("hello C4")
=> 8

queue = Dispatch::Queue.concurrent
queue.dispatch do
puts "Asynchronous dispatch FTW!"
end

it provides features that
Objective-C lacks

regular expressions,
tail-call optimization,
namespaces,
mixins,
operator overloading,
runtime evaluation…

What do you lose when going
from Objective-C to MacRuby?

static typing

JVM : Scala Cocoa : ?

Where are we now?

almost 0.5

SVN trunk is stable
(macruby.org)

nightly builds for 10.6 at
macruby.icoretech.org

What does the future hold?

Last summer I had an internship at Apple.
My views here, however, represent that of an open-source contributor,
and not an Apple employee. Any speculations on the future of MacRuby
are entirely mine and are in no way representative of any plans, attitudes,
or future directions that Apple may take. This presentation is neither
sponsored nor endorsed by Apple.
Apple: please donʼt sue me.

performance improvements

compatibility

not yet

Possible? Yes.
Certain? No

ahead-of-time compiler

MacRuby → x86/ARM machine code

full mode: packed with interpreter

restricted mode:
no eval(), no interpreter

compliant with Appleʼs restrictions
on interpreters in iPhone apps

we need garbage collection on
the iPhone

Stay Informed
@lrz
@importantshock
@benstiglitz
@MacRuby @vincentisambart
@mattaimonetti
@alloy