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std::unique_lock<Mutex>::swap - cppreference.com

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std::unique_lock

void swap( unique_lock& other ) noexcept;

 (since C++11)

Exchanges the internal states of the lock objects.

Parameters

other - the lock to swap the state with

Return value

(none)

Example

Run this code

#include <iostream>
#include <mutex>

int main()
{
    std::mutex mtx1;
    std::unique_lock<std::mutex> guard1(mtx1);
    std::unique_lock<std::mutex> guard2;
    guard2.swap(guard1);
    
    if (!guard1 && guard2)
        std::cout << "swapped success\n";
    
    return 0;
}

Output: 

swapped success

See also

specializes the std::swap algorithm
(function template) [edit]