定义一个具有许多(或无限)参数的方法 [英] Define a method that has many (or infinite) arguments

问题描述

NSArray 的 initWithObjects: 方法接受一个不确定的参数列表:

The initWithObjects: method of NSArray takes an indefinite list of arguments:

NSMutableArray *array = [[NSMutableArray alloc]initWithObjects:(id), ..., nil

我怎样才能像这样定义我自己的方法?

How can I define my own method like this?

- (void)CustomMethod:????? <= want to take infinite arguments {

}

推荐答案

无限参数"是可变参数，使用它们的方法称为可变参数方法.您可以按照与 NSMutableArray 示例相同的方式定义它们.苹果的技术问答有一个如何实现的例子

The "infinite arguments" are variable arguments and the methods that use them are called variadic methods. You define them the same way as your NSMutableArray example. Apple's Technical Q&A has an example of how to implement it.

- (void) appendObjects:(id) firstObject, ...
{
    id eachObject;
    va_list argumentList;
    if (firstObject) // The first argument isn't part of the varargs list,
    {                                   // so we'll handle it separately.
        [self addObject: firstObject];
        va_start(argumentList, firstObject); // Start scanning for arguments after firstObject.
        while ((eachObject = va_arg(argumentList, id))) // As many times as we can get an argument of type "id"
            [self addObject: eachObject]; // that isn't nil, add it to self's contents.
        va_end(argumentList);
    }
}

nil 参数的原因是让您知道何时到达列表的末尾.NSLog 和 printf 之类的函数不需要最后一个参数为 nil 因为它可以计算格式字符串中的说明符(%d、%s 等等...)

The reason for the nil argument is so that you know when you have reached the end of the list. Functions like NSLog and printf do not require the last argument to be nil because it can count the number of specifiers in the format string (%d, %s etc...)

这篇关于定义一个具有许多(或无限)参数的方法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！