CFAbsoluteTimeGetCurrent

1

调试函数耗时的利器CFAbsoluteTimeGetCurrent

 

   CFAbsoluteTime start = CFAbsoluteTimeGetCurrent();   // do something    CFAbsoluteTime end = CFAbsoluteTimeGetCurrent();    NSLog(@"time cost: %0.3f", end - start);

 

 

2 随机数

    double nextValue = sin(CFAbsoluteTimeGetCurrent())

 

        + ((double)rand() / (double)RAND_MAX);//rand()返回值[0,RAND_MAX]