WWDC 2013 - Advances in Objective-C (404) Summary

WWDC 2013 - Advances in Objective-C (404) Summary

Using a Framework

#import model issue

Header fragility
Non-scalable compile time

pre-compiled headers help significantly - maintenance burden / namespace pollution

Modules solve these issues

@import iAd;

Doesn't need to parse headers
Local macro definitions have no effect on framework API
Autolinking - don't need to "link binary with libraries"

Selective import

@import iAd.ADBannerView;

Using Modules

#import and #include automatically mapped to @import
No source changes required
Mac OS X Mail shows 40% faster compile time with modules - didn't manage pre-compiled headers well
For old project, enables it manually through the GUI

Build Settings / Apple LLVM 5.0 - Language - Modules / Enable Modules

Modules are not available for user framework

Tools support for modernisation

Edit / Refactor / Convert to Modern Objective-C Syntax …

Explicit Enums

NS_ENUM, NS_OPTIONS

Tagged Pointers

Added to 64 bit Cocoa
For small value like objects => stores object in the pointer itself => no malloc/free

NSNumber, NSDate, etc.
Performance => 3x times more space efficient, 106 times faster to allocate/destroy

LSB 4 bits are not used from 64 bit CPU => to align pointer address

Use the bottom bit as discriminator bit for a tagged pointer

Garbage Collection

Replaced by ARC
Deprecated with OS X 10.8

Common CF APIs allow implicit bridging

Old: NSString *str = (__bridge NSString *)CFDictionaryGetValue(_dict, @"key);
New: NSString *str = CFDictionaryGetValue(_dict, @"key);

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