std::weak_ptr::swap - cppreference.com (original) (raw)
| Member functions |
|---|
| weak_ptr::weak_ptr |
| weak_ptr::~weak_ptr |
| weak_ptr::operator= |
| Modifiers |
| weak_ptr::reset |
| weak_ptr::swap |
| Observers |
| weak_ptr::use_count |
| weak_ptr::expired |
| weak_ptr::lock |
| weak_ptr::owner_before |
| weak_ptr::owner_hash(C++26) |
| weak_ptr::owner_equal(C++26) |
| Non-member functions |
| swap(std::weak_ptr) |
| Helper classes |
| atomicstd::weak\_ptr(C++20) |
| Deduction guides(C++17) |
| 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
#include
#include
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 sp1 = std::make_shared(100);
std::shared_ptr sp2 = std::make_shared(200);
std::weak_ptr wp1 = sp1;
std::weak_ptr 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...