R.21:不需要共享所有权时应该使用unique_ptr而不是shared_ptr
Reason(原因)
A unique_ptr is conceptually simpler and more predictable (you know when destruction happens) and faster (you don't implicitly maintain a use count).
unique_ptr从概念上更简单,动作更加可预见(你知道析构动作什么时候发生)而且更快(不需要隐式维护使用计数)。
Example, bad(反面示例)
This needlessly adds and maintains a reference count.
不必要地增加和维护参照计数。
void f()
{
shared_ptr<Base> base = make_shared<Derived>();
// use base locally, without copying it -- refcount never exceeds 1
} // destroy base
This is more efficient:
下面的代码更高效:
void f()
{
unique_ptr<Base> base = make_unique<Derived>();
// use base locally
} // destroy base
(Simple) Warn if a function uses a Shared_pointer with an object allocated within the function, but never returns the Shared_pointer or passes it to a function requiring a Shared_pointer&. Suggest using unique_ptr instead.
(简单)如果函数使用shared_ptr管理其内局部分配的对象,但是从来没有返回该智能指针或者将其传递个一个需要shared_ptr&的函数,发出警告。建议使用unique_ptr。
原文链接
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#r21-prefer-unique_ptr-over-shared_ptr-unless-you-need-to-share-ownership
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