iOS OC 计算代码执行耗时

CFAbsoluteTimeGetCurrent()函数能够以毫秒为单位计算当前时间与2001.1.1差值。

- (void)viewDidLoad {
    [super viewDidLoad];
    
    CFAbsoluteTime start = CFAbsoluteTimeGetCurrent();
    // do something

    CFAbsoluteTime end = CFAbsoluteTimeGetCurrent();

    NSLog(@"%f", end - start);
}