如何获取一段代码的执行时间：
id object = @"ss";
CFTimeInterval startTime = CACurrentMediaTime();
{
for (size_t i = 0; i< 1000; i++) {
@autoreleasepool {
NSMutableArray * mutableArray = [NSMutableArray array];
for (size_t j = 0; j < 1000; j++) {
[mutableArray addObject:object];
}
}
}
}
CFTimeInterval endTime = CACurrentMediaTime();
NSLog(@"Total Runtime = %g s",endTime - startTime);