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).
| lhs, rhs | - | smart pointers whose contents to swap |
(none).
Constant.
#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...
| swaps the values of two objects (function template) |
|
| swaps the contents (public member function) |
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https://en.cppreference.com/w/cpp/memory/weak_ptr/swap2