Objective C的实现方法，需要的参数数组 [英] Objective c implement method which takes array of arguments

问题描述

熙

是否有人知道如何实现目标C的方法，将采取的参数数组作为参数，如：

Does anybody know how to implement an method in objective c that will take an array of arguments as parameter such as:

[NSArray arrayWithObjects:@"A",@"B",nil];

此方法的方法声明为：

The method declaration for this method is:

+ (id)arrayWithObjects:(id)firstObj...

我似乎无法做出这样的方法我自己。我做了以下内容：

I can't seem to make such method on my own. I did the following:

+ (void) doSometing:(id)string manyTimes:(NSInteger)numberOfTimes;

[SomeClass doSometing:@"A",@"B",nil manyTimes:2];

这会给warningtoo许多争论的功能'doSometing：manyTimes：

It will give the warningtoo many arguments to function 'doSometing:manyTimes:'

谢谢了。

推荐答案

省略号（...）是从C继承;你可以用它只能作为在通话的最后一个参数（你已经错过了你的榜样相关的逗号）。因此，在你的情况下，你可能想：

The ellipsis (...) is inherited from C; you can use it only as the final argument in a call (and you've missed out the relevant comma in your example). So in your case you'd probably want:

+ (void)doSomethingToObjects:(id)firstObject, ...;

或者，如果你想计数是明确的，能想到的措辞很好的一种方式：

or, if you want the count to be explicit and can think of a way of phrasing it well:

+ (void)doManyTimes:(NSInteger)numberOfTimes somethingToObjects:(id)firstObject, ...;

您就可以使用普通的C方法处理椭圆，它驻留在STDARG.H。这里有那些的快速文档，例如用法是：

You can then use the normal C methods for dealing with ellipses, which reside in stdarg.h. There's a quick documentation of those here, example usage would be:

+ (void)doSomethingToObjects:(id)firstObject, ...
{
    id object;
    va_list argumentList;

    va_start(argumentList, firstObject);
    object = firstObject;

    while(1)
    {
        if(!object) break; // we're using 'nil' as a list terminator

        [self doSomethingToObject:object];
        object = va_arg(argumentList, id);
    }

    va_end(argumentList);
}

编辑：添加，响应于注释。你不能交给你的省略号到另一个函数，它接受一个省略号的各种事情，由于传递和C语言处理函数调用（这是由Objective-C的继承，尽管不是很明显的话）的方式。相反，你往往会通过va_list的。例如。

additions, in response to comments. You can't pass the various things handed to you in an ellipsis to another function that takes an ellipsis due to the way that C handles function calling (which is inherited by Objective-C, albeit not obviously so). Instead you tend to pass the va_list. E.g.

+ (NSString *)doThis:(SEL)selector makeStringOfThat:(NSString *)format, ...
{
    // do this
    [self performSelector:selector];

    // make string of that...

    // get the argument list
    va_list argumentList;
    va_start(argumentList, format);

    // pass it verbatim to a suitable method provided by NSString
    NSString *string = [[NSString alloc] initWithFormat:format arguments:argumentList];

    // clean up
    va_end(argumentList);

    // and return, as per the synthetic example
    return [string autorelease];
}

这篇关于Objective C的实现方法，需要的参数数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！