我寫了下面的示例代碼,看看ARC如何工作爲什麼弱的NSString屬性不能在iOS中發佈?
@property (nonatomic, weak) NSString *myString;
@property (nonatomic, weak) NSObject *myObj;
@end
@implementation ViewController
@synthesize myString = _myString;
@synthesize myObj = _myObj;
- (void) viewDidAppear:(BOOL)animated
{
NSLog(@"Appearing Obj: !%@!",self.myObj);
NSLog(@"Appearing String: !%@!",self.myString);
}
- (void)viewDidLoad
{
self.myObj = [[NSObject alloc] init];
self.myString = [[NSString alloc] init];
NSLog(@"Loading Obj %@",self.myObj);
NSLog(@"Loading String: !%@!",self.myString);
}
然而令人驚訝的我得到這些結果:
2012-06-19 15:08:22.516 TESTER[4041:f803] Loading Obj (null)
2012-06-19 15:08:22.517 TESTER[4041:f803] Loading String: !!
2012-06-19 15:08:22.533 TESTER[4041:f803] Appearing Obj: !(null)!
2012-06-19 15:08:22.535 TESTER[4041:f803] Appearing String: !!
正如你所看到的,OBJ得到釋放正常,但我的字符串(這也是一個弱財產)不打印出null ...爲什麼不呢?
是你在'myString'中設置的字符串是否通過改變字符串文字(類似於@「Hello world!」)? –