如何将向量(或类似向量)传递到可变参数模板中 [英] How to pass a vector (or similar) into a variadic template

问题描述

假设我有以下代码:

template <typename... Args>
void DoSomething(const Args&... args)
{
    for (const auto& arg : {args...})
    {
        // Does something
    }
}

现在让我们说我是从另一个函数调用此函数，并想传入一个 std :: vector (或以某种方式修改向量，使其可以与此结合使用)

Now let's say I'm calling this from another function, and want to pass in an std::vector (or somehow modify the vector in such a way that it could be used with this)

void DoSomethingElse()
{
    // This is how I'd use the function normally
    DoSomething(50, 60, 25);

    // But this is something I'd like to be able to do as well
    std::vector<int> vec{50, 60, 25};
    DoSomething(??); // <- Ideally I'd pass in "vec" somehow
}

反正有这样做吗?我还考虑过使用 std :: initializer_list 而不是可变参数模板，但是问题仍然在于我无法传递现有数据.

Is there anyway to do this? I've also considered using std::initializer_list instead of variadic templates, but the issue still remains that I have no way to passing in existing data.

谢谢.

推荐答案

这里是使用SFINAE的一种方法.传递一个元素，就可以认为它是在范围内for-loop 中起作用的一个元素.

Here is one approach that uses SFINAE. Pass one element and it will be assumed it's something that works in a ranged for-loop.

如果您传递几个参数，它将构造一个向量并对其进行迭代.

If you pass several arguments it constructs a vector and iterates over that.

#include <iostream>
#include <type_traits>
#include <vector>

template <typename... Args, typename std::enable_if<(sizeof...(Args) > 1), int>::type = 0>
void DoSomething(const Args&... args)
{
    for (auto& a : {typename std::common_type<Args...>::type(args)...})
    {
        cout << a << endl;
    }
}

template <typename Arg>
void DoSomething(Arg& arg)
{
    for (auto a : arg)
    {
        std::cout << a << std::endl;
    }
}

int main() {
    DoSomething(10, 50, 74);

    std::vector<int> foo = {12,15,19};
    DoSomething(foo);
    return 0;
}

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