once.cpp

std::function<void()> once(const std::function<void()>& callback)
{
    return [&callback]() {
        static bool called = false;
        if (!called) {
            called = true;
            callback();
        }
    };
}

bool MyClass::init()
{
    static auto wuhu = once([](){ log("WUHU!"); });
    wuhu();
}