C ++：非临时const引用 [英] C++: non-temporary const reference

问题描述

我需要写一个类，它的构造函数需要一个对象的常量引用并存储在本地。

I need to write a class whose constructor takes a constant reference to a object and stores it locally.

为了避免大多数常见的错误，我可以预见，我'd只接受非临时的引用（即：引用lvalue）。

In order to avoid most common mistakes I can foresee, I'd like to only accept references to non-temporary (ie: references to lvalues).

如何编写一个函数，

当然，即使是非临时性的也可能超出范围，从而打破我的阶级行为，但我相信，不允许临时引用我将避免大多数错误。

Of course even a non-temporary could go out of scope and thus break my class behavior, but I believe that by disallowing temporary references I will avoid most mistakes.

推荐答案

如果要存储引用并需要在构造函数已完成，可能最好的构造函数接受一个指针：

If you are going to store a reference and need to use it after the constructor has completed, it's probably best for the constructor to take a pointer:

struct C {
    C(const X* p) : p_(p) { }

    const X* p_;
};

这样，几乎可以保证你不会有一个指向临时的指针code> X 做一些真正的蠢事，比如重载一元& 来返回 this ）。

This way, it's pretty much guaranteed that you won't have a pointer to a temporary (unless X does something really dumb, like overloading the unary & to return this).

如果构造函数接受一个指针，那么该类的用户也需要注意 X 对象，它们传递给构造函数。

If the constructor takes a pointer, it's also clearer to users of the class that they need to pay attention to the lifetime of the X object they pass to the constructor.

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