如何将可变数量的参数传递给可变参数函数 [英] How to pass variable number of args to a variadic function

问题描述

我有一个带有签名的可变参数函数:

I have a variadic function with the signature:

- (id)initWithNumVertices:(NSUInteger)inCount, ...;

但我不知道如何根据变量数量的顶点构造省略号部分.这怎么办?

But I cannot figure out how to construct the ellipsis part from a variable number of vertices. How can this be done?

抱歉，我不是在寻求一种编写此函数的方法，而是寻求一种使用未知 数量的变量来调用它的方法.该函数采用结构而不是对象.

sorry I wasn't asking for a way to write this function, I'm asking for a way to call it, using an unknown number of variables. The function takes structs and not objects.

如果参数的数量是已知的，我可以这样做:

If the number of arguments is known, I can do this:

[[MyObject alloc] initWithNumVertices:4, v[0], v[1], v[2], v[3]];

但是当顶点数未知时我怎么称呼它?

But how can I call this when the number of vertices is unknown?

推荐答案

如果在编译时不知道参数的数量，我认为不可能调用可变参数函数.如果您想避免使用 NSArray 的开销，将多个 C 结构传递给方法的标准方法是使用标准 C 数组.

I don't think it's possible to call a variadic function if the number of arguments is not known at compile time. If you want to avoid the overhead of using an NSArray, the standard way of passing multiple C structs to a method would be using standard C arrays.

- (id)initWithVertices:(Vertex *)vertices count:(NSUInteger)count;

NSIndexPath 的 -indexPathWithIndexes:length: 是一个也使用这种模式的例子，还有很多其他的，它在 Cocoa 中相当常见.

NSIndexPath's -indexPathWithIndexes:length: is an example where this pattern is also used, there are various others, it's fairly common in Cocoa.

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