std::weak_ptr<T>::expired
From cppreference.com
bool expired() const noexcept;
|
(since C++11) | |
Equivalent to use_count() == 0. The destructor for the managed object may not yet have been called, but this object's destruction is imminent (or may have already happened).
Parameters
(none)
Return value
true if the managed object has already been deleted, false otherwise.
Notes
If the managed object is shared among threads, it is only meaningful when expired() returns true.
Example
Demonstrates how expired is used to check validity of the pointer.
Run this code
#include <iostream>
#include <memory>
std::weak_ptr<int> gw;
void f()
{
if (!gw.expired())
std::cout << "gw is valid\n";
else
std::cout << "gw is expired\n";
}
int main()
{
{
auto sp = std::make_shared<int>(42);
gw = sp;
f();
}
f();
}
Output:
gw is valid
gw is expired