C ++ 11将“ this”作为std :: make_shared的参数传递 [英] C++11 Passing 'this' as paramenter for std::make_shared

问题描述

我正在尝试使用std :: make_shared

I'm trying to pass 'this' to the constructor using std::make_shared

示例：

// headers
class A 
{
public:
   std::shared_ptr<B> createB();
}


class B 
{
private:
   std::shared_ptr<A> a;

public:
   B(std::shared_ptr<A>);
}


// source
std::shared_ptr<B> A::createB()
{
   auto b = std::make_shared<B>(this); // Compiler error (VS11 Beta)
   auto b = std::make_shared<B>(std::shared_ptr<A>(this)); // No compiler error, but doenst work
   return b;
}

但是，这不能正常工作，我建议如何正确通过

However this does not work properly, any suggestions how I can properly pass this as an argument?

推荐答案

我认为您可能想要的是 shared_from_this 。

I think what you probably want here is shared_from_this.

// headers
class A : std::enable_shared_from_this< A >
{
public:
   std::shared_ptr<B> createB();
}


class B 
{
private:
   std::shared_ptr<A> a;

public:
   B(std::shared_ptr<A>);
}


// source
std::shared_ptr<B> A::createB()
{
   return std::make_shared<B>( shared_from_this() );
}

---

更新为包含 David Rodriguez的评论：

请注意， shared_from_this（）不应从不调用尚未由<$管理的对象c $ c> shared_ptr 。这是有效的：

Note that shared_from_this() should never be called on an object that isn't already managed by a shared_ptr. This is valid:

shared_ptr<A> a( new A );
a->createB();

尽管以下情况导致不确定的行为（试图调用 delete a 上的c $ c>）：

While the following leads to undefined behaviour (attempting to call delete on a):

A a;
a.createB();

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