迭代不同类型 [英] Iterating over different types

问题描述

给出以下代码：

struct Window{
    void show();
    //stuff
}w1, w2, w3;

struct Widget{
    void show();
    //stuff
}w4, w5, w6;

struct Toolbar{
    void show();
    //stuff
}t1, t2, t3;

我想要显示 ：

for (auto &obj : {w3, w4, w5, t1})
    obj.show();

但是这不会编译，因为 std :: initializer_list< T& / code>中的中找不到 T ，事实上没有真正的 T 。我不想创建类型擦除类型，因为所需的代码量和不必要的运行时开销。我如何正确地写我的循环，使得 obj 的类型分别推导到概念列表中的每个项目？

However this does not compile since the std::initializer_list<T> in the for-loop cannot deduce T and in fact there is not really a T that would fit. I don't want to create a type erasure type because of the amount of code required and the unnecessary runtime overhead. How do I correctly write my loop so that the type of obj is deduced for every item in the conceptual list separately?

推荐答案

在现代C ++中，您可以使用折叠表达式，通过应用成员函数遍历异质参数：

In modern C++ you'd use fold expressions, to "walk through" your heterogenous arguments applying the member function:

auto Printer = [](auto&&... args) {
    (args.show(), ...);
};

Printer(w1, w2, w3, w4, w5, w6, t1, t2, t3);

演示

您可以在我的 blog

这篇关于迭代不同类型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！