C++ std::unique_ptr 的推荐用法
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Recommended usage of std::unique_ptr
提问by Mushy
What are recommended uses of a std::unique_ptras to specifically where, when, and how is it is best used?
a 的推荐用途是什么std::unique_ptr，特别是在何处、何时以及如何最好地使用它？
I discovered:
我发现：
I already know:
我已经知道：
std::unique_ptrwas developed in C++11 as a replacement forstd::auto_ptr- That a
std::unique_ptrhas no reference counting and "owns" object it points to - There is no copy/assign with a
std::unique_ptr - When I need a unique pointer,
std::unique_ptris the go to structure
std::unique_ptr是在 C++11 中开发的，作为替代std::auto_ptr- a
std::unique_ptr没有引用计数并且“拥有”它指向的对象 - 没有复制/分配
std::unique_ptr - 当我需要一个唯一的指针时，
std::unique_ptr是转到结构
What I would like to know:
我想知道的是：
- Is using a
std::unique_ptrever preferable (other than uniqueness) to something
else? What do I gain in this situation? - If so, under what circumstances and when?
- Given the need for move semantics, would this make a
std::unique_ptrless favorable
overall? - If a
std::shared_ptrwould suffice for dynamic memory management in nearly every situation, why does having at my disposal astd::unique_ptrmatter (again, other
than uniqueness)?
- 使用
std::unique_ptr比其他东西更可取的（除了唯一性）
吗？在这种情况下我能得到什么？ - 如果是，在什么情况下，什么时候？
- 考虑到移动语义的需要，这是否会使
总体上
std::unique_ptr不太有利
？ - 如果 a
std::shared_ptr几乎在所有情况下都足以进行动态内存管理，那么为什么我可以随意使用它std::unique_ptr（同样，
除了唯一性之外）？
回答by Kate Gregory
In theory, you should use unique_ptrfor all pointers unless you know you want to share it, in which case you should use shared_ptr. The reason is that unique_ptrhas less overhead since it doesn't count references.
理论上，您应该使用unique_ptrfor 所有指针，除非您知道要共享它，在这种情况下，您应该使用shared_ptr. 原因是它的unique_ptr开销较少，因为它不计算引用。
However, a unique_ptris movable but not copyable, so using one as a member variable can require you to write more code (eg a move constructor), passing one by value means you'll need to use std::moveand so on. As a result some people use shared_ptrout of laziness, because it's just easier, and the perf difference may not be significant for their app.
但是， aunique_ptr是可移动的但不可复制，因此将其用作成员变量可能需要您编写更多代码（例如移动构造函数），按值传递一个意味着您需要使用std::move等等。因此，有些人shared_ptr出于懒惰而使用它，因为它更容易，而且性能差异对于他们的应用程序来说可能并不重要。
Finally a raw pointer is fine for observation - pointer uses that can never affect lifetime. Careful choice of the right pointer type can give those who read your code a good understanding of what you are doing. For more, see Herb Sutter's essay, Elements of C++ Style, specifically the "no delete" section.
最后，原始指针适合观察 - 指针使用永远不会影响生命周期。仔细选择正确的指针类型可以让阅读你代码的人很好地理解你在做什么。有关更多信息，请参阅 Herb Sutter 的文章Elements of C++ Style，特别是“不可删除”部分。
