迭代双精度列表，其中for-each不在Objective-C中工作

Question

我正在努力在Objective-C中平均任意多个数字，到目前为止这是我的方法：

-(double)average:(double)num, ...
{
    va_list args;
    va_start(args, num);

    double currentAverage = num;
    long long timesAveraged = 1;
    for(double d in args)
        currentAverage = ((currentAverage * timesAveraged) + d) / ++timesAveraged;//Error occurs on this line
    return currentAverage;

}

但是，当我编译它时，我收到一条错误，指出“Selector element does not have a valid object type”，所以我的第一个解决方案是将方法更改为以下内容：

-(double)average:(double)num, ...
{
    va_list args;
    va_start(args, num);

    double currentAverage = num;
    long long timesAveraged = 1;
    for(NSNumber *d in args)
        currentAverage = ((currentAverage * timesAveraged) + [d doubleValue]) / ++timesAveraged;//Error occurs on this line
    return currentAverage;

}

然而，现在它给了我一个令人不安的类似错误“Expression does not have a valid object type”。

我显然做错了。有关如何做到这一点的任何建议吗？

解决方案

---

我已经能够通过编写这样的方法来编译文件：

-(double)average:(double)num, ...
{
    va_list args;
    va_start(args, num);

    double currentAverage = num;
    long long timesAveraged = 1;
    for (NSNumber *arg = [NSNumber numberWithDouble:num]; arg != nil; arg = va_arg(args, NSNumber*))
    {
        currentAverage = ((currentAverage * timesAveraged) + [arg doubleValue]) / ++timesAveraged;
    }
    va_end(args);
    return currentAverage;

}

Answer 1

由于trudyscousin提到快速枚举在这里不起作用。您还应该使用va_arg从参数列表中提取数据。在此处阅读更多相关信息：http://cocoawithlove.com/2009/05/variable-argument-lists-in-cocoa.html