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std::shared_ptr<T>::swap

From cppreference.com
< cpp‎ | memory‎ | shared 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)
 
std::shared_ptr
Member functions
Modifiers
shared_ptr::swap
Observers
(until C++20*)
Non-member functions
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
functions (until C++26*)
Helper classes
 
void swap( shared_ptr& r ) noexcept;
(since C++11)

Exchanges the stored pointer values and the ownerships of *this and r. Reference counts, if any, are not adjusted.

[edit] Parameters

r - smart pointer to exchange the contents with

[edit] Return value

(none)

[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> p1 = std::make_shared <Foo>(100);
 std::shared_ptr <Foo> p2 = std::make_shared <Foo>(200);
 auto print = [&]()
 {
 std::cout << " p1=" << (p1 ? p1->print() : "nullptr");
 std::cout << " p2=" << (p2 ? p2->print() : "nullptr") << '\n'; 
 };
 print();
 
 p1.swap(p2);
 print();
 
 p1.reset();
 print();
 
 p1.swap(p2);
 print(); 
}

Output:

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