将 auto_ptr 分配给 weak_ptr

Question

我仍在探索 C++ 11。所以我很确定我做错了什么。但是我就是想不通问题所在。

我有以下代码：

MyClass::MyClass(const PlayerEventListener* eventListener)
{
   weak_ptr<PlayerEventListener> _listener;
   std::auto_ptr<PlayerEventListener> autoPtr;
   autoPtr.reset(const_cast<PlayerEventListener*> (eventListener));
   // I get error for this line
   _listener = autoPtr;
}

我收到以下错误：没有可行的重载'='

但是下面的代码可以正常编译：

MyClass::MyClass(const PlayerEventListener* eventListener)
{
   weak_ptr<PlayerEventListener> _listener;
   std::shared_ptr<PlayerEventListener> sharedPtr;
   sharedPtr.reset(const_cast<PlayerEventListener*> (eventListener));
   // I get error for this line
   _listener = sharedPtr;
}

有人可以解释为什么我不能将自动指针转换为弱指针吗？

Answer 1

weak_ptr is an object that holds a safe reference to an object actually held by shared_ptr, not auto_ptr. Therefore, there is no any overloaded operator= that could provide assigning auto_ptr to weak_ptr in the implementation of weak_ptr. It can be verified by compiling this example code 并查看错误

In constructor 'MyClass::MyClass(const PlayerEventListener*)':
21:14: error: no match for 'operator=' (operand types are 'std::weak_ptr<PlayerEventListener>' and 'std::auto_ptr<PlayerEventListener>')

记住： 根据http://www.cplusplus.com/reference/memory/auto_ptr/：

This class template (auto_ptr) is deprecated as of C++11. unique_ptr is a new facility with a similar functionality, but with improved security (no fake copy assignments), added features (deleters) and support for arrays. See unique_ptr for additional information.

将 auto_ptr 分配给 weak_ptr

Assign auto_ptr to weak_ptr

c++

gcc

clang

c++11