public member function
<memory>
shared_ptr<element_type> lock() const noexcept;
Lock and restore weak_ptr
Returns a shared_ptr with the information preserved by the weak_ptr object if it is not expired.
If the weak_ptr object has expired (including if it is empty), the function returns an empty shared_ptr (as if default-constructed).
Because shared_ptr objects count as an owner, this function locks the owned pointer, preventing it from being released (for at least as long as the returned object does not releases it).
This operation is executed atomically.
Example
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// weak_ptr::lock example
#include <iostream>
#include <memory>
int main () {
std::shared_ptr<int> sp1,sp2;
std::weak_ptr<int> wp;
// sharing group:
// --------------
sp1 = std::make_shared<int> (20); // sp1
wp = sp1; // sp1, wp
sp2 = wp.lock(); // sp1, wp, sp2
sp1.reset(); // wp, sp2
sp1 = wp.lock(); // sp1, wp, sp2
std::cout << "*sp1: " << *sp1 << '\n';
std::cout << "*sp2: " << *sp2 << '\n';
return 0;
}
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Output:
See also
- weak_ptr::reset
- Reset pointer (public member function)
- weak_ptr::expired
- Check if expired (public member function)