我什么时候应该使用原始指针而不是智能指针?

2021-12-13 00:00:00 pointers c++ boost smart-pointers

阅读后这个答案，看起来最好使用 智能指针 尽可能多，并将普通"/原始指针的使用减少到最低限度.

After reading this answer, it looks like it is a best practice to use smart pointers as much as possible, and to reduce the usage of "normal"/raw pointers to minimum.

这是真的吗?

推荐答案

不，这不是真的.如果一个函数需要一个指针并且与所有权无关，那么我强烈认为应该传递一个常规指针，原因如下:

No, it's not true. If a function needs a pointer and has nothing to do with ownership, then I strongly believe that a regular pointer should be passed for the following reasons:

  • 没有所有权，因此您不知道要传递什么样的智能指针
  • 如果你传递一个特定的指针，比如shared_ptr，那么你将无法传递，比如，scoped_ptr
  • No ownership, therefore you don't know what kind of a smart pointer to pass
  • If you pass a specific pointer, like shared_ptr, then you won't be able to pass, say, scoped_ptr

规则是这样的――如果你知道一个实体必须拥有对象的某种所有权，总是使用智能指针――它给你您需要的所有权类型.如果没有所有权的概念，从不使用智能指针.

The rule would be this - if you know that an entity must take a certain kind of ownership of the object, always use smart pointers - the one that gives you the kind of ownership you need. If there is no notion of ownership, never use smart pointers.

示例 1:

void PrintObject(shared_ptr<const Object> po) //bad
{
    if(po)
      po->Print();
    else
      log_error();
}

void PrintObject(const Object* po) //good
{
    if(po)
      po->Print();
    else
      log_error();
}

示例 2:

Object* createObject() //bad
{
    return new Object;
}

some_smart_ptr<Object> createObject() //good
{
   return some_smart_ptr<Object>(new Object);
}

相关文章