访问此指针的shared_ptr [英] Accessing shared_ptr for this pointer

问题描述

有一种方法可以访问shared_ptr：

Is there a way to get access to the shared_ptr for this:

例如。

#include <boost/enable_shared_from_this.hpp>
#include <boost/shared_ptr.hpp>
#include <cassert>

class Y: public boost::enable_shared_from_this<Y>
{
public:
    void foo();
    void bar();
    boost::shared_ptr<Y> f()
    {
        return shared_from_this();
    }
};

void Y::foo() 
{
   boost::shared_ptr<Y> p(this);
   boost::shared_ptr<Y> q = p->f();
   q->bar();
   p.reset();
   q.reset();
}

void Y::bar()
{
   std::cout << __func__ << std::endl;
}

int main()
{
   Y y;
   y.foo();
}

当我运行程序时，我在执行bar后得到一个segafult。
我明白了seg-fault的原因。

When I run the program I get a segafult after execution of bar. I do understand the reason for seg-fault.

我的最终目标是有一个弱指针，然后回调。

My final goal is to have a weak pointer and then a call back.

感谢

推荐答案

y 的生命周期由共享指针管理，或者当它创建的堆栈帧终止时超出范围。

Either y's lifetime is managed by shared pointers or it goes out of scope when the stack frame it's created on terminates. Make up your mind and stick with it.

如果这段代码能以某种方式工作，它会破坏 y 两次，一次当 main 结束时超出范围，并且一旦最后一个 shared_ptr 消失了。

If this code could work somehow, it would destroy y twice, once when it went out of scope at the end of main and once when the last shared_ptr went away.

也许你想要：

int main()
{
   std::shared_ptr<Y> y = std::make_shared<Y>();
   y->foo();
}

这里，实例被销毁时，其最后 shared_ptr 消失。这可能发生在 main 的结尾，但如果 foo squirrels一份 shared_ptr ，它可以延长对象的生命周期。它可以松开一个弱指针，也许在全局对象的析构函数中告诉对象已经走了。

Here, the instance is destroyed when its last shared_ptr goes away. That may occur at the end of main, but if foo squirrels away a copy of the shared_ptr, it can extend the lifetime of the object. It can squirrel away a weak pointer, and perhaps tell in the destructor of the global object that the object is gone.

弱指针的意思是能够促进它到一个强大的指针，可以延长对象的生命。如果无法动态管理对象的生命周期，这将无法工作。

The point of a weak pointer is to be able to promote it to a strong pointer which can extend the object's lifetime. This won't work if there's no way to dynamically manage the object's lifetime.

这篇关于访问此指针的shared_ptr的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！