Question

我有一个执行此操作的弹出系统（GUI）：

// creates popup with two possible answer-buttons
if (timeToEat())
  callPopup(ID_4, "What to eat?", "Cake", "Cookies!"); 

//elsewhere in code i check for key presses
if (popupAnswered(ID_4,0)) // clicked first button in popup
  eatCake();

if (popupAnswered(ID_4,1)) // clicked second button in popup
  eatCookiesDamnit();

我可以使用某种lambda / callback来安排它，如下所示。因此功能＆＃34;仍然是＆＃34;并且可以在按下按钮时激活（返回值）。

谢谢！

if (timeToEat())
   callPopup("What to eat?", "Cake", "Cookies!"){
       <return was 0 :>  eatCake(); break;
       <return was 1 :>  eatCookies(); break;
}

Answer 1

您可以向callPopup添加延续参数：

void callPopup(int id, std::function<void(int)> f)
{
    if (something)
        f(0);
    else
        f(1);
}

// ...

callPopup(ID_4, [](int x) { if (x == 0) eatCake(); });

或者您可以添加另一个功能层并使用返回值：

std::function<void(std::function<void(int)>)> 
callPopup(int id)
{
        return [](std::function<void(int)> f) { f(something ? 0 : 1); }
}

// ...
callPopup(ID_4)([](int x) { if (x == 0) ... ;});
// or
void popupHandler(int);
auto popupResult = callPopup(ID_4);
// ...
popupResult(popupHandler);

Answer 2

您可以将选项与操作相关联，然后执行与单击的

相关联的操作

using PopupActions = std::map<std::string, std::function<void()>>;

void callPopup(int id, std::string prompt, PopupActions actions)
{
    for (auto & pair : actions)
        // create button with text from pair.first and on-click from pair.second
    // show buttons
}

if (timeToEat())
   callPopup(ID_4, "What to eat?", { 
       { "Cake!", [this]{ eatCake(); } }
       { "Cookies!", [this]{ eatCookies(); } }
   });
}

C ++ lambda / callback弹出窗口？

2 个答案: