不影响方法单独延迟返回值

能不能实现单独延迟返回值，不对整个方法造成影响？

-(CGFloat)getValue{
// code implementation
return floatvalue; // return float value with some delay.
}

使用block回调值时延迟

- (void)ayncGetValue:(void(^)(id value))returnBlock {

  dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, 10.f * NSEC_PER_SEC); // delay 10 seconds
  dispatch_after(popTime, dispatch_get_main_queue(), ^{
    returnBlock(@"hello block");
  });
}
// Usage
[obj ayncGetValue:^(id value) {
  // continue  
}];

两种方法，喜欢哪个用哪个吧

第一种：
需要在方法中用到sleep：

-(CGFloat)getValue{
// code implementation

 sleep(5);
return floatvalue; // return float value with some delay.
}

第二种：

使用performSelector:

[self performSelector:@selector(getValue) withObject:nil afterDelay:5];

-(void)getValue
{
// code implementation

  [self performSelector:@selector(getValue:) withObject:value afterDelay:2];
}

-(CGFloat)getValue:(CGFloat *)float1
{
  return float1;
}