为什么switch总是运行default？ （有休息;包括） [英] Why does switch always run default? (with break; included)

问题描述

当我使用开关语句如图所示。

从其他线程和论坛，我发现这可能与有关， getch（），并返回 char 以及 \\\
。

我已经尝试了一个小时，但我不能解决这个问题。我使用 getch（）的原因是：

现在我的代码部分：

  //设置游戏字段
 generateField（）; 
 setPlayerStart（）; 
 
 // printGameInfo（）;要生产
 
 //开始游戏while循环
 int userInput; 
 
 do {
 // system（cls）;禁用测试目的
 printField（）; 
 userInput = getch（）; 
 
 switch（userInput）{
 case 72：{// ARROW UP 
 cout< 1What< endl; // ALSO FOR TESTING PURPOSES 
 break; 
} 
 
 case 80：{//向下
 cout<< 2What< endl; 
 break; 
} 
 
 case 75：{// ARROW LEFT 
 cout<< 3What< endl; 
 break; 
} 
 
 case 77：{// ARROW RIGHT 
 cout< 4What< endl; 
 break; 
} 
 
 case 113：{//q
 return false; //退出游戏
} 
 
默认值：{
 cout< Default ...< endl; 
} 
} 
} while（userInput！= 5）; 
  

解决方案

由于这是Windows，您可以使用 ReadConsoleInput 以读取关键事件。我把这些部分分成了函数，但我不认为 handleInput 的返回语义是非常棒的。

  #include< iostream> 
 #include< stdexcept> 
 #include< windows.h> 
 
 HANDLE getStdinHandle（）{
 HANDLE hIn; 
 if（（hIn = GetStdHandle（STD_INPUT_HANDLE））== INVALID_HANDLE_VALUE）{
 throw std :: runtime_error（无法获取标准输入句柄。 
} 
 
 return hIn; 
} 
 
 WORD readVkCode（HANDLE hIn）{
 INPUT_RECORD rec; 
 DWORD numRead; 
 while（ReadConsoleInput（hIn，& rec，1，& numRead）&& numRead == 1）{
 if（rec.EventType == KEY_EVENT&& rec.Event。 KeyEvent.bKeyDown）{
 return rec.Event.KeyEvent.wVirtualKeyCode; 
} 
} 
 
 throw std :: runtime_error（无法读取输入。 
} 
 
 bool handleInput（WORD vk）{
 switch（vk）{
 case VK_UP：
 std :: cout< up\\\
; 
 break; 
 
 case VK_DOWN：
 std :: cout<< down\\\
; 
 break; 
 
 case VK_LEFT：
 std :: cout<< left\\\
; 
 break; 
 
 case VK_RIGHT：
 std :: cout<< right\\\
; 
 break; 
 
 case'Q'：//它是Windows; ASCII是安全的
 return true; 
} 
 
 return false; 
} 
 
 int main（）{
 try {
 auto hIn = getStdinHandle（）; 
 
 while（auto vk = readVkCode（hIn））{
 if（handleInput（vk））{
 return 0; 
} 
} 
} catch（const std :: exception& ex）{
 std :: cerr< ex.what（）; 
 return 1; 
} 
} 
  

其他有用的链接：

• GetStdHandle


• INPUT_RECORD li>
  
• KEY_EVENT


• 虚拟键代码

C++ newbie trying to make a simple text game on a 2D array.

When I use the switch statement as shown. It will always print the default value, regardless of what else happens.

From other threads and forums I found it probably has something to do with the getch() and that it returns the char as well as \n.

I have tried for an hour now but I can not solve this. The reason I use getch() is this: C++ change canonical mode in windows (for reference).

Part of my code now:

//Set up game field
generateField();
setPlayerStart();

//printGameInfo(); TO BE MADE

//Start game while loop
int userInput;

do{
    //system("cls"); DISABLED FOR TESTING PURPOSES
    printField();
    userInput = getch();

    switch(userInput){
        case 72:{ //ARROW UP
            cout << "1What" << endl; //ALSO FOR TESTING PURPOSES
            break;
        }

        case 80:{ //ARROW DOWN
            cout << "2What" << endl;
            break;
        }

        case 75:{ //ARROW LEFT
            cout << "3What" << endl;
            break;
        }

        case 77:{ //ARROW RIGHT
            cout << "4What" << endl;
            break;
        }

        case 113:{ //"q"
            return false; //Quit game
        }

        default:{
            cout << "Default..." << endl;
        }
    }
} while(userInput != 5);

解决方案

Since this is Windows, you can use ReadConsoleInput to read key events. I've separated the parts into functions, but I don't really think the return semantics of handleInput is all that great.

#include <iostream>
#include <stdexcept>
#include <windows.h>

HANDLE getStdinHandle() {
    HANDLE hIn;
    if ((hIn = GetStdHandle(STD_INPUT_HANDLE)) == INVALID_HANDLE_VALUE) {
        throw std::runtime_error("Failed to get standard input handle.");
    }

    return hIn;
}

WORD readVkCode(HANDLE hIn) {
    INPUT_RECORD rec;
    DWORD numRead;
    while (ReadConsoleInput(hIn, &rec, 1, &numRead) && numRead == 1) {
        if (rec.EventType == KEY_EVENT && rec.Event.KeyEvent.bKeyDown) {
            return rec.Event.KeyEvent.wVirtualKeyCode;
        }
    }

    throw std::runtime_error("Failed to read input.");
}

bool handleInput(WORD vk) {
    switch (vk) {
        case VK_UP:
            std::cout << "up\n";
            break;

        case VK_DOWN:
            std::cout << "down\n";
            break;

        case VK_LEFT:
            std::cout << "left\n";
            break;

        case VK_RIGHT:
            std::cout << "right\n";
            break;

        case 'Q': //it's Windows; ASCII is safe
            return true;
    }

    return false;
}

int main() {
    try {
        auto hIn = getStdinHandle();

        while (auto vk = readVkCode(hIn)) {
            if (handleInput(vk)) {
                return 0;
            }
        }
    } catch (const std::exception &ex) {
        std::cerr << ex.what();
        return 1;
    }
}

Other useful links:

• GetStdHandle
• INPUT_RECORD
• KEY_EVENT
• Virtual key codes

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