Objective-C - ARC(Automatic Reference Counting)自動引用技術詳解

標籤：objective   arc   arc特點與判斷準則   自動引用技術   

ARC特點與判斷準則

/* ARC的判斷準則：只要沒有強指標指向對象，就會釋放對象 1.ARC特點 1> 不允許調用release、retain、retainCount 2> 允許重寫dealloc，但是不允許調用[super dealloc] 3> @property的參數  * strong ：成員變數是強指標（適用於OC物件類型）  * weak ：成員變數是弱指標（適用於OC物件類型）  * assign : 適用於非OC物件類型 4> 以前的retain改為用strong 指標分2種： 1> 強指標：預設情況下，所有的指標都是強指標 __strong 2> 弱指標：__weak */int main(){    Dog *d = [[Dog alloc] init];    Person *p = [[Person alloc] init];    p.dog = d;    d = nil;    NSLog(@"%@", p.dog);    return 0;}void test(){    // 錯誤寫法（沒有意義的寫法）    __weak Person *p = [[Person alloc] init];    NSLog(@"%@", p);    NSLog(@"------------");}

@class Dog;@interface Person : NSObject@property (nonatomic, strong) Dog *dog;@property (nonatomic, strong) NSString *name;@property (nonatomic, assign) int age;@end

@implementation Person- (void)dealloc{    NSLog(@"Person is dealloc");    // [super dealloc];}@end

@interface Dog : NSObject@end

@implementation Dog- (void)dealloc{    NSLog(@"Dog is dealloc");}@end

ARC循環參考問題

/** *   當兩端循環參考的時候，解決方案： 1> ARC 1端用strong，另1端用weak 2> 非ARC 1端用retain，另1端用assign */int main(){    Person *p = [[Person alloc] init];    Dog *d = [[Dog alloc] init];    p.dog = d;    d.person = p;    return 0;}

@class Dog;@interface Person : NSObject@property (nonatomic, strong) Dog *dog;@end

@implementation Person- (void)dealloc{    NSLog(@"Person--dealloc");}@end

@class Person;@interface Dog : NSObject@property (nonatomic, weak) Person *person;@end

@implementation Dog- (void)dealloc{    NSLog(@"Dog--dealloc");}@end

Objective-C - ARC(Automatic Reference Counting)自動引用技術詳解