使用std :: initializer_list作为成员变量 [英] using std::initializer_list as a member variable

问题描述

我有一个 A 类，它使用 initializer_list 并将其存储为成员变量。

I have a class A that takes an initializer_list and stores it as a member variable.

class A
{
public:
    A(std::initializer_list<std::string> il) :
        m_il(il)
    {}

    std::initializer_list<std::string> m_il;
};

另一类 B 具有 A 作为成员变量，默认使用 initializer_list

Another class B has A as a member variable that is default initialized using the initializer_list

class B
{
public:
    B()
    {
        std::cout << *m_a.m_il.begin() << std::endl;
    }

    A m_a { "hello", "bye" };
};

现在，当我在main中运行此代码时，它什么也不会打印。

Now when I run this code in main, it prints nothing.

int main()
{
    B b;
}

上面的代码为什么不打印 hello ？我对 std :: initializer_list 的用法不正确吗？

Why did the code above not print hello? Is my usage of std::initializer_list incorrect?

推荐答案

std :: initializer_list 不会复制其基础对象。它并不是要用作容器。相反，您应该做的是将其存储在其他内容中，例如 std :: vector ：

Copying a std::initializer_list does not copy its underlying objects. It's not meant to be used as a container. What you should be doing instead is storing it in something else, like a std::vector:

class A
{
public:
    A(std::initializer_list<std::string> il) :
        m_il(il)
    {}

    std::vector<std::string> m_il;
};

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