是否有任何情况下，RValue参考（&&）的返回是有用的？ [英] Is there any case where a return of a RValue Reference (&&) is useful?

问题描述

当函数应返回RValue参考时，是否有原因？一种技术或诀窍，或成语或模式？

Is there a reason when a function should return a RValue Reference? A technique, or trick, or an idiom or pattern?

MyClass&& func( ... );

我知道一般返回引用，但有时我们这样做，不是我们（ T& T :: operator = （T）只是一个惯用的例子）。但是 T&& func（...）？有没有什么一般的地方，我们会从中获益？

I am aware of the danger of returning references in general, but sometimes we do it anyway, don't we (T& T::operator=(T) is just one idiomatic example). But how about T&& func(...)? Is there any general place where we would gain from doing that? Probably different when one writes library or API code, compared to just client code?

推荐答案

有一些情况下，当适当的时候，但它们相对较少。当您想要允许客户端从数据成员移动时，会出现一个示例。例如：

There are a few occasions when it is appropriate, but they are relatively rare. The case comes up in one example when you want to allow the client to move from a data member. For example:

template <class Iter>
class move_iterator
{
private:
    Iter i_;
public:
    ...
    value_type&& operator*() const {return std::move(*i_);}
    ...
};

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