Question

说出你的代码是：

cout << "You wake up in a room. There is a small lit candle and a door. What do you do?" << endl;
        string startout;
        getline(cin, startout);
            if (startout == "Door" || startout == "DOOR" || startout == "door" || startout == "Open Door" || startout == "open door" || startout == "OPEN DOOR" || startout == "Open door" || startout == "Open the door" || startout == "open the door")  {
                cout << " " << endl;
                cout << "You move to the door but its too dark to see anything besides the outline of it." << endl;
            } else if (startout == "Candle" || startout == "CANDLE" || startout == "candle" || startout == "Pick Up Candle" || startout == "PICK UP CANDLE" || startout == "pick up candle" || startout == "Pick up candle") {
                cout << "You pick up the candle then move to the door. With the light from the candle you can see the door well. What do you do?" << endl;
            };

如果使用代码的人除了＆＃34; Door＆＃34;之外的其他东西。或＆＃34;蜡烛＆＃34; （或任何变体），代码将重新启动if语句，以便重新询问第一个问题？

Ex：用户输入：＆＃34;跳舞＆＃34;

输出：＆＃34;我不明白＆＃34;跳舞＆＃34;。你做了什么？＆＃34;

或类似的东西。

Answer 1

首先，你需要一个更好的解析器。至少，把表格或某种地图中的合法值，带有指针行动。然后将输入包装在函数中：

typedef void (*     ActionPointer)();  //  Or whatever you need.
typedef std::map< std::string, ActionPointer, CaseInsensitiveCmp >
                    ActionMap;

ActionPointer
getAction( ActionMap const& legalValues )
{
    std::string line;
    if ( ! std::getline( std::cin ) ) {
        //  Error on std::cin...  Probably fatal.
    }
    ActionMap::const_iterator action = legalValues.find();
    return action == legalValues.end()
        ? nullptr
        : action->second;
}

然后你可以这样写：

std::cout << "You wake up in a room. There is a small lit candle and a door."
             " What do you do?" << std::endl;
ActionPointer nextAction = getAction();
while ( nextAction == nullptr ) {
    std::cout << "I don't understand.  What do you do?" << std::endl;
    nextAction = getAction();
}
(*nextAction)();

如果您想在错误消息中获得更多信息，可以安排使用指针和该信息返回struct（仍在测试指针）。

Answer 2

您可以在外部添加while(true)循环，并添加if条件，该条件会在正确输入时中断。

此外，在getline命令之后，在else if conditon：

之后添加else条件

else
    cout << "I don't understand " << startout << ". What do you do?" << endl;

在另一个if和else if子句中，添加break;命令。

Answer 3

你想跑，直到他们输入正确的东西？这非常简单。你应该使用一个循环。

循环通常是一个语句块，它会在条件满足之前重复。例如，一个好的循环是：

Repeat the program until the string equals Door or Candle。

条件，我看你已经比较熟悉了。然后让我向您介绍while循环块的语法，我认为它最适合您的情况（do while是另一个适合您的循环，但它是＆＃39;稍微复杂一点来解释）。编辑：我正在使用rain的评论更改代码：

string startout=""; // Initiallizing it before the while loop, so it could be used inside it.
cout << "You wake up in a room. There is a small lit candle and a door. What do you do?" << endl;
while(startout !="door" && startout !="candle") // Do the following actions in this block until startout equals "Door" or "Candle".
{ // start of a while block
    getline(cin, startout);
    if (startout.tolower().find("door")!=npos) // If the string contains any variation of door:
    {
        cout << " " << endl;
        cout << "You move to the door but its too dark to see anything besides the outline of it." << endl;
    } 
    else if (startout.tolower().find("candle")!=npos) // same, with candle. Much more elegant, like thomas said. 
    {
            cout << "You pick up the candle then move to the door. With the light from the candle you can see the door well. What do you do?" << endl;
    }  
    else
    {
       cout << "I don't understand " << startout << ". What do you do?" << endl; // If you didn't get what you want, ask for another string and restart.
    }
} // end of the while block.

Answer 4

for (;;)
    cout << "You wake up in a room. There is a small lit candle and a door. What do you do?" << endl;
    string startout;
    getline(cin, startout);
    if (startout == "Door" || startout == "DOOR" || 
        startout == "door" || startout == "Open Door" || 
        startout == "open door" || startout == "OPEN DOOR" || 
        startout == "Open door" || startout == "Open the door" ||
        startout == "open the door")  {

        cout << " " << endl;
        cout << "You move to the door but its too dark to see anything besides the outline of it." << endl;
        break;
    } else if (startout == "Candle" || startout == "CANDLE" || 
               startout == "candle" || startout == "Pick Up Candle" || 
               startout == "PICK UP CANDLE" || 
               startout == "pick up candle" || 
               startout == "Pick up candle") {
        cout << "You pick up the candle then move to the door. With the light from the candle you can see the door well. What do you do?" << endl;
        break;
    }; 
}

这不是最优雅的方式，但你明白了。

C ++如何重启if语句？

4 个答案: