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std::swap(std::weak_ptr)

From cppreference.com
< cpp‎ | memory‎ | weak ptr
 
 
Memory management library
(exposition only*)
Uninitialized storage (until C++20)
(until C++20*)
(until C++20*)

(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
(C++11)(until C++23)
 
 
Defined in header <memory>
template< class T >
void swap( std::weak_ptr <T>& lhs, std::weak_ptr <T>& rhs ) noexcept;
(since C++11)

Specializes the std::swap algorithm for std::weak_ptr . Swaps the contents of lhs and rhs. Calls lhs.swap(rhs).


[edit] Parameters

lhs, rhs - smart pointers whose contents to swap

[edit] Return value

(none)

[edit] Complexity

Constant.

[edit] Example

Run this code
#include <iostream>
#include <memory>
#include <string>
 
struct Foo {
 Foo(int _val) : val(_val) { std::cout << "Foo...\n"; }
 ~Foo() { std::cout << "~Foo...\n"; }
 std::string print() { return std::to_string (val); }
 int val;
};
 
int main()
{
 std::shared_ptr <Foo> sp1 = std::make_shared <Foo>(100);
 std::shared_ptr <Foo> sp2 = std::make_shared <Foo>(200);
 std::weak_ptr <Foo> wp1 = sp1;
 std::weak_ptr <Foo> wp2 = sp2;
 auto print = [&]() {
 auto p1 = wp1.lock();
 auto p2 = wp2.lock();
 std::cout << " p1=" << (p1 ? p1->print() : "nullptr");
 std::cout << " p2=" << (p2 ? p2->print() : "nullptr") << '\n'; 
 };
 print();
 
 std::swap (wp1, wp2);
 print();
 
 wp1.reset();
 print();
 
 std::swap (wp1, wp2);
 print(); 
}

Output:

Foo...
Foo...
 p1=100 p2=200
 p1=200 p2=100
 p1=nullptr p2=100
 p1=100 p2=nullptr
~Foo...
~Foo...

[edit] See also

swaps the values of two objects
(function template) [edit]
swaps the contents
(public member function) [edit]
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