如何使用类模板参数来更改参数调用和函数签名？ [英] How to use class template argument to change argument calls and function signatures?

问题描述

我试图找到一种方法来设计类模板，以便传递 int 值，并且几个函数签名以及参数列表都依赖于该值。

I am trying to find way to design a class template so that an int value is passed, and several function signatures as well as argument lists are dependent on this value.

特别是考虑 MyClass ：

template <int N>
class MyClass {
    typedef SomeType<int, int, int, /* ... N times*/ > MyDepType;
    myFunction(std::string arg0, std::string  arg1, /* ...*/ std::string  argN) { /* do stuff */};
 public:
    MyClass() {
        someFunction(float arg0, float arg1, /* ...*/ float argN);   // <
        someOtherFunction(boost::bind(&MyClass::myFunction, this, _1, _2, /*...*/ _N));
    };
};

我希望能够表达私有typedef调用和<$ c的签名$ c> myFunction 并将参数列表传递给外部函数 someFunction 和 someOtherFunction 我无法编辑/重写。
是否可以使用C ++ 11标准来实现这一目标？

I'd like to be able to express both the private typedef call, the signature of myFunction and the argument list passed to external functions someFunction and someOtherFunction, which I can't edit/rewrite. Is there a way to achieve this, using the C++11 standard?

推荐答案

您可以使用 std :: index_sequence （C ++ 14，但可以在SO上找到C ++ 11的实现）：

You might use std::index_sequence (C++14, but implementation in C++11 can be found on SO):

template <std::size_t, typename T>
using always_t = T;

template <std::size_t ... Is>
class MyClassImpl {
    using MyDepType = SomeType<always_t<Is, int>...>;
    void myFunction(always_t<Is, std::string>... args) { /* do stuff */}
 public:
    MyClass() {
        void someFunction(always_t<Is, std::float>... args);
        someOtherFunction([this](always_t<Is, const std::string&>... args) {
            return myFunction(args...);
        });

        // 
        std::array<std::string, sizeof...(Is)> strings = {std::to_string(Is)...};
        myFunction(strings[Is]...);
    };
};

template <std::size_t N>
using MyClass = MyClassImpl<std::make_index_sequence<N>>;

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