std::weak_ptr<T>::swap
From cppreference.com
void swap( weak_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(){returnstd::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(); wp1.swap(wp2); print(); wp1.reset(); print(); wp1.swap(wp2); print();}
Output:
Foo... Foo... p1=100 p2=200 p1=200 p2=100 p1=nullptr p2=100 p1=100 p2=nullptr ~Foo... ~Foo...
