IOS第二天多线程-02一次性代码
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#import "HMViewController.h" #import "HMImageDownloader.h" @interface HMViewController () //@property (nonatomic, strong) HMImageDownloader *downloader; @end @implementation HMViewController - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. // self.downloader = [[HMImageDownloader alloc] init]; } - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { NSLog(@"----touchesBegan"); static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ //只能执行一次 NSLog(@"----once"); HMImageDownloader *downloader = [[HMImageDownloader alloc] init]; [downloader download]; }); } @end
没有失败, 只有放弃...