c++ - 从类中返回可 move 的成员变量

Question

class foo{
public:
    bar steal_the_moveable_object();
private:
    bar moveable_object;
};

main(){
    foo f;
    auto moved_object= f.steal_the_moveable_object();
}

如何实现 steal_the_movebale_object 将 moveable_object move 到 moved_object 中？

Answer 1

您可以直接在返回语句中简单地 move 成员:

class foo
{
public:
    bar steal_the_moveable_object()
    {
        return std::move(moveable_object);
    }
private:
    bar moveable_object;
};

请注意，这可能不是一个好主意。考虑改用以下方法，以便该方法只能在 R-Values 上调用:

class foo
{
public:
    bar steal_the_moveable_object() && // add '&&' here
    {
        return std::move(moveable_object);
    }
private:
    bar moveable_object;
};

int main()
{
    foo f;
    //auto x = f.steal_the_moveable_object(); // Compiler error
    auto y = std::move(f).steal_the_moveable_object();

    return 0;
}