CocoaHeads 14 Mai 2013

mardi 28 mai 13

Backelite...

...recrute !mardi 28 mai 13

Au programme

• Accessors Vs Direct access to properties

• Design Pattern : Categories

• Design Pattern : Associative Storage

• La chaine Météo!

mardi 28 mai 13

iVar : Accessors/Direct access

• Performance ?

• Risks / Limits ?

mardi 28 mai 13

property Using setter (ms)Using Direct Access

(ms)

strong + nonatomic 9 6

weak + nonatomic 30 30

unsafe_unretained + nonatomic 0,8 0,2

strong + atomic 9 6

iPhone 3GS/iOS5 + 10,000 affectactions. (average based on several tests.)

iVar : Accessors/Direct accessPerformance?

mardi 28 mai 13

• Direct affectation don’t use the property attributes (atomic)

• KVO/KVC needs accessors,

• Don’t use accessor methods in init methods and dealloc (You may have override your accessors)

iVar : Accessors/Direct accessRisk / Limits?

mardi 28 mai 13

Design Pattern: Categories• Add new methods to existing classes

#import "IBSHelper.h"@interface IBSHelper (FileName)+ (NSString*)filenameForGeolocData;+ (NSString*)filenameForBrandCodeData;+ (NSString*)filenameForTradData;+ (NSString *)currentLanguage;+ (NSString *)currentLanguageForDownload;+ (NSURL*)urlForGeolocData;+ (NSURL*)urlForBrandData;+ (NSURL*)urlForTradData;@end

mardi 28 mai 13

Design Pattern: Categories• Organize/split complexity

mardi 28 mai 13

Design Pattern: Categories• Makes easy to support multiple OS versions

@interface UITableView (BkUICore)

- (void) bkRegisterNibName:(NSString *)nibName forCellReuseIdentifier:(NSString *)identifier;- (id) bkDequeueReusableCellWithIdentifier:(NSString *)identifier;

@end

@interface UIViewController (BkUICore)

- (void) bkDismissModalViewControllerAnimated:(BOOL)animated;- (void) bkPresentViewController:(UIViewController *)controller animated:(BOOL)animated;

@end

mardi 28 mai 13

Design Pattern: Categories

• Categories can be used to declare either instance methods or class methods but are not usually suitable for declaring additional properties.

One other design pattern can help us !Associated storage

@interface UITableView (BkUICore)

- (void) bkRegisterNibName:(NSString *)nibName forCellReuseIdentifier:(NSString *)identifier;- (id) bkDequeueReusableCellWithIdentifier:(NSString *)identifier;

@end

mardi 28 mai 13

Design Pattern: Associative references

http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40008048

Objective-C programs interact with the runtime system at three distinct levels: through Objective-C source code; through methods defined in the NSObject class of the Foundation framework; and through direct calls to runtime functions.

mardi 28 mai 13

Design Pattern: Associative references

//nsobjet.h@interface NSObject

+ (Class)superclass;+ (Class)class;- (BOOL)respondsToSelector:(SEL)aSelector;+ (BOOL)conformsToProtocol:(Protocol *)protocol;

//runtime.h

OBJC_EXPORT Class class_getSuperclass(Class cls) OBJC_EXPORT Class object_getClass(id obj) OBJC_EXPORT BOOL class_respondsToSelector(Class cls, SEL sel) OBJC_EXPORT BOOL class_conformsToProtocol(Class cls, Protocol *protocol)

Some of the NSObject methods simply query the runtime system for information. These methods allow objects to perform introspection.

mardi 28 mai 13

• A way to add simulate new properties to an existing class !

Design Pattern: Associative references

static const char nibsAssocKey;

@implementation UITableView (BkUICore)- (void) bkRegisterNibName:(NSString *)nibName forCellReuseIdentifier:(NSString *)identifier{ if ([self respondsToSelector:@selector(registerNib:forCellReuseIdentifier:)]) { [self registerNib:[UINib nibWithNibName:nibName bundle:[NSBundle mainBundle]] forCellReuseIdentifier:identifier]; //NS_AVAILABLE_IOS(5_0) } else { NSMutableDictionary *nibs = objc_getAssociatedObject(self, &nibsAssocKey); if (nil == nibs) { nibs = [NSMutableDictionary dictionary]; objc_setAssociatedObject(self, &nibsAssocKey,

nibs, OBJC_ASSOCIATION_RETAIN); } [nibs setValue:nibName forKey:identifier]; }}@end

mardi 28 mai 13

La chaine meteoIssue : How to add a new property on UINavigationBar

• Subclass UINavigationBar, dumbass !

• Use associated storage !

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La chaine meteo

mardi 28 mai 13

Other examples

• UIView + BkBadge

• UIView + BkLoader

....

mardi 28 mai 13

Thanks

mardi 28 mai 13