我在尝试理解ARC的工作方式,就我所知,我可能在这里做错了些什么。这是我正在使用的代码:
接口:
@interface ViewController : UIViewController{
}
@property (strong, nonatomic) NSString * myString ;
@property (weak, nonatomic) NSString * myPointer ;
实施:
- (void)viewDidLoad{
[super viewDidLoad];
self.myString = @"Hello world!" ; // myString is strong
self.myPointer = self.myString ; // myPointer var is weak
[self performSelector:@selector(makeNilMyValue) withObject:nil afterDelay:1];
[self performSelector:@selector(printValues) withObject:nil afterDelay:2];
}
- (void) makeNilMyValue{
self.myString = nil ;
}
- (void) printValues{
NSLog(@"myString: %@", self.myString) ;
NSLog(@"myPointer: %@", self.myPointer) ;
}
执行完这段代码后,我得到了:
2012-02-26 11:40:41.652 test1[933:207] myString: (null)
2012-02-26 11:40:41.653 test1[933:207] myPointer: Hello world!
如果我没记错,由于myPointer是弱引用,它不应该保留对象的内容。因此,它应该显示nil而不是“Hello World!”。
我做错了什么?
根据Caleb的答案,我又创建了另一个弱指针,请见下面的代码:
- (void)viewDidLoad{
[super viewDidLoad];
self.myString = @"Hello world!" ; // myString is strong
self.myPointer = self.myString ; // myPointer var is weak
self.myPointer2 = self.myString ; // myPointer2 var is weak
[self performSelector:@selector(makeNilMyValue) withObject:nil afterDelay:1];
[self performSelector:@selector(printValues) withObject:nil afterDelay:2];
}
- (void) makeNilMyValue{
self.myPointer2 = @"value changed!" ;
self.myString = nil ;
}
- (void) printValues{
NSLog(@"myString: %@", self.myString) ;
NSLog(@"myPointer: %@", self.myPointer) ;
}
重点是我仍然得到了与之前相同的答案:
2012-02-26 12:08:13.426 test1[1333:207] myString: (null)
2012-02-26 12:08:13.427 test1[1333:207] myPointer: Hello world!