class Class {
public:
    void method0() {
        std::unique_lock<std::mutex>(m_mutex);
        // Do something
    }

    void method1() {
        std::unique_lock<std::mutex>{m_mutex};
        // Do something
    }

private:
    std::mutex m_mutex;
};

// Thread 0:
while(true) cls.method0();

// Thread 1:
while(true) cls.method1();