使用const std :: unique_ptr进行pimpl习语 [英] Using const std::unique_ptr for pimpl idiom

问题描述

在 Herb Sutter在CppCon16上的演讲中，他建议使用 const std :: unique_ptr （大约10分钟）。

In Herb Sutter's talk at CppCon16 he suggested writing pimpl idiom with const std::unique_ptr (roughly 10 minutes in).

这应该如何与move构造函数/赋值一起使用？ c ++ 17中有东西吗？我什么都找不到。

How is this supposed to work with move constructors/assignments? Is there something in c++17? I couldn't find anything.

推荐答案

如果您的类应该是永不为空的，则可以使用非const唯一的ptr（默认移动/分配）是不合适的。

If your class is supposed to be never-empty, a non-const unique ptr (with default move/assigns) is not appropriate. The move ctor and move assign will both empty the rhs.

一个const唯一的ptr会禁用这些自动方法，如果要移动，则必须将其写入

A const unique ptr will disable these automatic methods, and if you want move you will have to write it within the impl (and a bit of glue outside).

我会亲自用自己想要的语义编写一个值ptr（然后让编译器编写该粘合），但是从a开始

I would personally write a value ptr with the semantics I want (then let compiler write the glue), but starting with a const unique_ptr sounds reasonable as a first pass.

如果放松永不虚空，并使其几乎永不虚空，那么现在您必须考虑很多先决条件

If you relax the never-empty, and make it almost never-empty, you now have to reason about preconditions of a lot of methods, and possible knock-on bugs.

C ++ 17消除了这种技术的最大成本，即难以返回值。

The biggest cost of this technique, difficulty in returning values, goes away with C++17.

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