ios 求助dispatch_after和 [NSTimer scheduledTimerWithTimeInterval: repeats: block]

[Happylege]

这两种定时器有啥区别？

如下代码执行结果怎么解释？

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
NSLog(@"dispatch_after 1001");
});

[NSTimer scheduledTimerWithTimeInterval:0.53 repeats:NO block:^(NSTimer * _Nonnull timer) {
NSLog(@"NSTimer 1002");
}];

// 执行结果
2020-02-24 10:55:39.255721+0800 ILGDemo[3833:454767] NSTimer 1002
2020-02-24 10:55:39.274360+0800 ILGDemo[3833:454767] dispatch_after 1001