【代碼筆記】iOS-GCD用法，筆記ios-gcd用法

【代碼筆記】iOS-GCD用法，筆記ios-gcd用法

代碼：

- (void)viewDidLoad{    [super viewDidLoad];    // Do any additional setup after loading the view.        //GCD的用法    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{                NSURL * url = [NSURL URLWithString:@"http://www.baidu.com"];        NSError * error;        NSString * data = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];        if (data != nil) {            dispatch_async(dispatch_get_main_queue(), ^{                NSLog(@"call back, the data is: %@", data);            });        } else {            NSLog(@"error when download:%@", error);        }    });        }