循环范围内的初始化列表 [英] Initializer list in a range for loop

问题描述

我有从单个超类型派生的不同类型的对象.我想知道在这样的循环范围内使用 std::initializer 列表是否有任何缺点:

I have objects of different types derived from a single super-type. I wonder if there are any disadvantages in using std::initializer list in a range for loop like this:

for(auto object: std::initializer_list<Object *>{object1, object2, object3}) {
}

是否完全可以且高效，还是使用数组更好?对我来说，std::array 解决方案似乎对编译器的限制更大，并且显式说明大小有一个缺点:

Is it completely OK and efficient or would it be better to use an array? To me the std::array solution seems to be more restrictive for the compiler and there is a disadvantage of explicitly stating the size:

for(auto object: std::array<Object*, 3>{object1, object2, object3}) {
}

是否有任何其他或更好的方法来迭代明确给定的对象列表?

Is there any other or nicer way of iterating over an explicitly given list of objects?

推荐答案

循环内部不需要使用冗长的std::initializer_list

There is no need to use the verbose std::initializer_list inside the loop

#include <iostream>
#include <initializer_list>

struct B { virtual int fun() { return 0; } };
struct D1 : B { int fun() { return 1; } };
struct D2 : B { int fun() { return 2; } };

int main()
{
    D1 x;
    D2 y;

    B* px = &x;
    B* py = &y;

    for (auto& e : { px, py })
            std::cout << e->fun() << "
";    
}

实例.

如果您想在不定义 px 和 py 的情况下即时执行此操作，您确实可以使用 std::initializer_list<B*>{ &x, &y } 在循环内.

If you want to do it on-the-fly without defining px and py, you can indeed use std::initializer_list<B*>{ &x, &y } inside the loop.

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