This document discusses Automatic Reference Counting (ARC) in iOS. It explains how ARC manages memory by automatically retaining and releasing objects, eliminating the need for manual memory management. Key points covered include how ARC handles strong and weak references, transitioning between non-ARC and ARC code, and some tips for using ARC in practice.

1. ARC iOS
(id:ninjinkun / @ninjinkun)

2. • Cocoa Touch
• ARC
• ARC
•
• ARC
•
• Tips
• GC

3. Cocoa Touch
• retain / relase
-(void)setName:(NSString *)newName {
name = [newName retain];
}
-(void)dealloc {
[name release];
[super dealloc]; 1 3 0
}
• Ownership
• Ownership retain
• Ownership release
• 0

4. Cocoa Touch
Autorelase
•
• autorelease
• release
• /
•

5. Cocoa Touch
Autorelase
•
• autorelease
• release
• /
•
-(void)buildNewName {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSMutableArray *array = [[[NSMutableArray alloc] init] autorelease];
[array addObject:@"hoge"];
[array addObject:@"fuga"];
[array addObject:@"piyo"];
name =[array componentsJoinedByString:@","];
[pool drain];
}

6. ARC
• Automatic Reference Counting
•
• iOS 5 / Mac OS X 10.7

7. ARC
•
•
• (GC)
• Static Analyzer

8. ARC
•
@interface NonARCObject : NSObject {
NSString *name;
}
-(id)initWithName:(NSString *)name;
@end
@implementation NonARCObject
-(id)initWithName:(NSString *)newName {
self = [super init];
if (self) {
name = [newName retain];
}
return self;
}
-(void)dealloc {
[name release];
[super dealloc];
}
@end

9. ARC
•
@interface ARCObject : NSObject {
NSString *name;
}
-(id)initWithName:(NSString *)name;
@end
@implementation ARCObject
-(id)initWithName:(NSString *)newName {
self = [super init];
if (self) {
name = newName;
}
return self;
}
@end

10. ARC
ARC
•
• …
•
•
•
•

11. ARC
__strong
•
• Ownership
•
• retain, release
-(void)buildNewName {
{
__strong NSMutableArray *array = [[NSMutableArray alloc] init];
[array addObject:@"hoge"];
[array addObject:@"fuga"];
[array addObject:@"piyo"];
name =[array componentsJoinedByString:@","];
}
}
!

12. ARC
__strong
•
• retain, dealloc relase
@interface ARCUser : NSObject {
__strong NSString *name;
}
@end
@implementation ARCUser
-(id)initWithName:(NSString *)newName {
self = [super init];
if (self) {
name = newName; // [newName retain]
}
return self;
}
-(void)dealloc {
// [name release]
}
@end

13. ARC
__weak
• __weak
•
• Ownership
• nil
•
• iOS 5
@interface ARCUser : NSObject {
__weak id delegate;
}
@end

14. ARC
__unsafe_unretainded
•
• assign
•
• iOS 4.3
@interface ARCUser : NSObject {
__unsafe_unretained id delegate;
}
@end

15. ARC
__autoreleasing
• autorelase
•
• @autorelasepool { }
-(NSArray *)comvertImageToJpeg:(NSArray *)files {
NSMutableArray *dataStore = [NSMutableArray array];
@autoreleasepool {
for (NSString *filePath in files) {
__autoreleasing UIImage *image = [[UIImage alloc]
initWithContentsOfFile:filePath];
NSData *data = UIImageJPEGRepresentation(image, 1.0);
[dataStore addObject:data];
}
}
return [dataStore copy];
}

16. ARC
• retain, release, autorelase
• retainCount
• [super dealloc]
• dealloc
-(void)dealloc {
delegate = nil;
}
• C __bridge
NSString *str = @"hogehoge";
CFStringRef strRef = (__bridge CFStringRef)str;
CFStringRef strRef = (__bridge_retained CFStringRef)str;

17. • ARC __strong
• __strong
__strong
__strong
__strong __strong
__strong

18. • iOS 5 __weak
• iOS 4.3 __unsafe_unretaind
• nil
__strong
__weak
__strong __strong
__strong

19. ARC
•

20. ARC
retain / relase
• -S
•
• _objc_release()
• _objc_retain()
• _objc_retainAutoreleasedReturnValue()

21. ARC
__weak
• _objc_storeWeak()
• 0 _objc_destroyWeak()
•
• nil
•
This document is licensed to ninjin@mac.com.

22. Blocks
• ARC
• self ?
•
• release
• BlocksKit
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
[button addEventHandler:^(id sender) {
[self showPhotoPickerView];
} forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];

23. Blocks
•
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
__unsafe_unretained id _self = self; // !?
[button addEventHandler:^(id sender) {
[_self showPhotoPickerView];
} forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];

24. Blocks
•
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
__unsafe_unretained id _self = self; // !?
[button addEventHandler:^(id sender) {
!?
[_self showPhotoPickerView];
} forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];

25. Tips
ARC
• -fno-objc-arc

26. Tips
ARC
• Static Library
• Static Library
• Workspace

27. Tips
• ARC
• iOS 5 __weak
• Blocks
• UI
• UI Blocks

28. GC
• GC
• iOS
•
•
• CPU

29. • ARC
• ( )
• __weak
• GC
•
• ( )
• ARC