std::swap(std::weak_ptr)
From cppreference.com
| Defined in header <memory>
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| 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).
Parameters
| lhs, rhs | - | smart pointers whose contents to swap |
Return value
(none)
Complexity
Constant.
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...
See also
| swaps the values of two objects (function template) | |
| swaps the contents (public member function) |