使用 args 传递函数并将值返回给另一个函数

Question

Is it possible to pass function with arguments like this:

int func(int num)
{
 return num;
}

to this function:

        template<class T>
        auto addTask(T task) -> std::future<decltype(task())>
        {
            auto wrapper = std::make_shared<std::packaged_task<decltype(task()) ()>>(std::move(task));
            {
                std::unique_lock<std::mutex> lock(mEventMutex);
                mTasks.emplace([=] {
                    (*wrapper)();
                });
            }
            mEventVar.notify_one();
            return wrapper->get_future();            
        }

I know how pass function without agrs like this:

void func()
{}

It will be just:

addTask(func);

but can't find where to place args. Is it possible?

Answer 1

You could use a lambda that calls the function:

addTask([some_value]()
{
    func(some_value);
});

---

Or rewrite addTask to use template parameter packs for possible arguments:

template<typename Func, typename ...Args>
auto addTask(Func task, Args... arguments) -> std::future<decltype(task(arguments...))>
{
    auto wrapper = std::make_shared<std::packaged_task<decltype(task(arguments...)) (Args...)>>(std::move(task));
    {
        std::unique_lock<std::mutex> lock(mEventMutex);
        mTasks.emplace([=] {
            (*wrapper)(std::forward<Args>(arguments)...);
        });
    }
    mEventVar.notify_one();
    return wrapper->get_future();         
}

addTask(func, some_value);