Question

我尝试学习如何使用GCD（THE DOC），并从apple文档中编写一些代码。但它无法在Xcode中编译。不确定我该怎么办呢。

- (void)viewDidLoad
{
    [super viewDidLoad];

    dispatch_source_type_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_get_main_queue());

    if (timer) {
        dispatch_source_set_timer(timer, dispatch_walltime(NULL, 0), 30ull * NSEC_PER_SEC, 1ull * NSEC_PER_SEC);
        dispatch_source_set_event_handler(timer, ^{
            NSLog(@"YES!");
        });
        dispatch_resume(timer);
    }

    // Do any additional setup after loading the view, typically from a nib.
}

错误：

/Users/sunfmin/Developments/GCDTests/GCDTests/ViewController.m:22:36: Implicit conversion of Objective-C pointer type 'dispatch_source_t' (aka 'NSObject<OS_dispatch_source> *') to C pointer type 'dispatch_source_type_t' (aka 'const struct dispatch_source_type_s *') requires a bridged cast
/Users/sunfmin/Developments/GCDTests/GCDTests/ViewController.m:22:28: Incompatible pointer types initializing 'dispatch_source_type_t' (aka 'const struct dispatch_source_type_s *') with an expression of type 'dispatch_source_t' (aka 'NSObject<OS_dispatch_source> *')
/Users/sunfmin/Developments/GCDTests/GCDTests/ViewController.m:25:35: Implicit conversion of C pointer type 'dispatch_source_type_t' (aka 'const struct dispatch_source_type_s *') to Objective-C pointer type 'dispatch_source_t' (aka 'NSObject<OS_dispatch_source> *') requires a bridged cast
/Users/sunfmin/Developments/GCDTests/GCDTests/ViewController.m:25:35: Incompatible pointer types passing 'dispatch_source_type_t' (aka 'const struct dispatch_source_type_s *') to parameter of type 'dispatch_source_t' (aka 'NSObject<OS_dispatch_source> *')
/Users/sunfmin/Developments/GCDTests/GCDTests/ViewController.m:26:43: Implicit conversion of C pointer type 'dispatch_source_type_t' (aka 'const struct dispatch_source_type_s *') to Objective-C pointer type 'dispatch_source_t' (aka 'NSObject<OS_dispatch_source> *') requires a bridged cast
/Users/sunfmin/Developments/GCDTests/GCDTests/ViewController.m:26:43: Incompatible pointer types passing 'dispatch_source_type_t' (aka 'const struct dispatch_source_type_s *') to parameter of type 'dispatch_source_t' (aka 'NSObject<OS_dispatch_source> *')
/Users/sunfmin/Developments/GCDTests/GCDTests/ViewController.m:29:25: Implicit conversion of C pointer type 'dispatch_source_type_t' (aka 'const struct dispatch_source_type_s *') to Objective-C pointer type 'dispatch_object_t' (aka 'NSObject<OS_dispatch_object> *') requires a bridged cast
/Users/sunfmin/Developments/GCDTests/GCDTests/ViewController.m:29:25: Incompatible pointer types passing 'dispatch_source_type_t' (aka 'const struct dispatch_source_type_s *') to parameter of type 'dispatch_object_t' (aka 'NSObject<OS_dispatch_object> *')

Answer 1

调度源的类型为dispatch_source_t，因此它应为

dispatch_source_t timer = ...

dispatch_source_type_t是dispatch_source_create()的第一个参数的类型，在您的情况下为DISPATCH_SOURCE_TYPE_TIMER。

Objective-C指针类型'dispatch_source_t'的隐式转换

1 个答案: