为什么C ++ CLI在托管类型上没有默认参数？ [英] Why C++ CLI has no default argument on managed types?

问题描述

以下行有错误默认参数不允许。

public ref class SPlayerObj{
private:

    void k(int s = 0){ //ERROR
    }
}

为什么C ++在托管类型上没有默认参数？

我想知道是否有办法修复这个问题。

Why C++ has no default argument on managed types ?
I would like to know if there is a way to fix this.

推荐答案

它有可选参数，它们看起来和C ++语法看起来不一样。可选参数是一种语言互操作问题。它必须由进行调用的语言实现，它生成实际使用默认参数的代码。这是一个棘手的问题，在一个语言，旨在使交互轻松，如C / C / CLI，你当然不知道什么语言将打电话。或者如果它甚至有可选参数的语法。 C＃语言直到版本4为止。

It does have optional arguments, they just don't look the same way as the C++ syntax. Optional arguments are a language interop problem. It must be implemented by the language that makes the call, it generates the code that actually uses the default argument. Which is a tricky problem in a language that was designed to make interop easy, like C++/CLI, you of course don't know what language is going to make the call. Or if it even has syntax for optional arguments. The C# language didn't until version 4 for example.

如果语言支持它，那么编译器如何知道默认值是什么。值得注意的是，VB.NET和C＃v4选择了不同的策略，VB.NET使用了一个属性，C＃使用了一个modopt。

And if the language does support it, how that compiler knows what the default value is. Notable is that VB.NET and C# v4 chose different strategies, VB.NET uses an attribute, C# uses a modopt.

你可以使用C ++中的[DefaultParameterValue] / CLI。但您不应该，结果无法预测。

You can use the [DefaultParameterValue] attribute in C++/CLI. But you shouldn't, the outcome is not predictable.

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