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std::weak_ptr::weak_ptr

From cppreference.com
< cpp‎ | memory‎ | weak ptr
Revision as of 15:41, 1 July 2013 by P12bot (Talk | contribs)

 
 
 
 
 
constexpr weak_ptr();
(1) (since C++11)
weak_ptr( const weak_ptr& r );
(2) (since C++11)
template< class Y >
weak_ptr( const weak_ptr<Y>& r );
(2) (since C++11)
template< class Y >
weak_ptr( const std::shared_ptr<Y>& r );
(2) (since C++11)

Constructs new weak_ptr that potentially shares an object with r.

1) Default constructor. Constructs empty weak_ptr.

2) Constructs new weak_ptr which shares an object managed by r. If r manages no object, *this manages no object too. The templated overloads don't participate in the overload resolution unless Y* is implicitly convertible to T*.

Contents

Parameters

r - a std::shared_ptr or std::weak_ptr that will be viewed by this std::weak_ptr

Exceptions

noexcept specification:  
noexcept
  

Example

#include <memory>
#include <iostream>
 
struct Foo {};
 
int main()
{
   std::weak_ptr<Foo> w_ptr;
 
   {
      auto ptr = std::make_shared<Foo>();
      w_ptr = ptr;
      std::cout << "w_ptr.use_count() inside scope: " << w_ptr.use_count() << '\n';
   }
 
   std::cout << "w_ptr.use_count() out of scope: " << w_ptr.use_count() << '\n';
}

Output:

w_ptr.use_count() inside scope: 1
w_ptr.use_count() out of scope: 0

See also

assigns the weak_ptr
(public member function) [edit]