当用户键入分隔符时停止 getline() 输入

Question

我正在尝试找到一种方法，当用户在我的练习应用程序中的 getline 函数中输入定界字符时，无需按 Enter 即可停止输入。

目前，只有当用户在输入定界字符后按下 Enter 时，来自 getline 的输入流才会中断，并且 cout 消息会向用户解释，但我更希望输入在按下定界符时简单地停止。

正在寻找有关如何在检测到指定字符时停止输入的建议。

这是我的完整代码：

#include <iostream>
#include <string>
#include <fstream>

using namespace std;

#define DEBUG 1 // 1 = enabled

int main()
{
    char takeFirstNonSpaceCharacter(string text);
    string message;
    char stopper;
    string stopperInput;

    cout << "Type the character with which you want to signal end of a message\n";
    cin >> stopperInput;
    cin.ignore(128, '\n'); //clean cin

    stopper = takeFirstNonSpaceCharacter(stopperInput); //in case input has white spaces
    cout << "Type your message, make it as long as you want.\n To finish typing enter the " << stopper << " symbol followed by Enter\n Input after the " << stopper << " symbol will be lost\n";

    getline(cin, message, stopper);
#if DEBUG == 1
    cout << message << '\n';
#endif
    system("pause");
    return 0;
}

char takeFirstNonSpaceCharacter(string text)
{
    string::const_iterator iter = text.begin();
    while (iter != text.end())
    {
        if (*iter != 32 || *iter != 10 || *iter != 9) //ascii: 32 = space, 10 = new line, 9 = horizontal tab
        {
            return *iter; //if its not space character then it must be a character (unless the user can somehow type for example [=10=] on keyboard)
        }
        else
        {
            iter++; //if its space
        }
    }
    return '[=10=]';
}

input/output 围绕这个（粗体是我的输入）

Type the character with which you want to signal end of a message

}

Type your message, make it as long as you want. To finish typing enter the } symbol followed by Enter Input after the } symbol will be lost

asdf}asdf

asdf

Answer 1

使用 standard-c/c++，您将无法访问控制台输入，直到用户使用 enter 发送它。唯一的方法是直接访问终端，但由于每个 OS 使用不同的控制台，因此需要 OS 特定的解决方案。

在 windows 上，您可以使用 <conio.h> 的 _getch() 或 WinApi ReadConsoleInput.

在 unix 上你可以使用 <termios.h> 或 <curses.h>

Crossplattform 库，适用于每个 OS:
NCurses

synchronet ciolib

PDcurses

这是 windows 的代码示例：

#include <conio.h>      // _getch()
#include <cctype>       // std::isspace
#include <string>       // std::getline
#include <iostream>     // std::cout
#include <algorithm>    // std::find_if_not

#define DEBUG

int main(void)
{
    int stopper;

    std::cout << "Type the character with which you want to signal end of a message" << std::endl;

    while (std::isspace(stopper = std::cin.get())) {} // oneliner instead of takeFirstNonSpaceCharacter
    std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); // flush the rest of 

    // alternative oneliner without the need of pressing enter
    // do { stopper = _getch(); } while (std::isspace(stopper));

    std::cout << "Type your message, make it as long as you want." << std::endl;
    std::cout << "To finish typing, enter the " << (char)stopper << " symbol followed by Enter" << std::endl;
    std::cout << "Input after the " << (char)stopper << " symbol will be lost" << std::endl;

    std::string message;
    for(int ch = _getch(); ch != stopper; ch = _getch()) {
        _putch(ch); // print it, so the user can see his input
        message.push_back(ch); // concat it to the message buffer
    };

#ifdef DEBUG
    std::cout << std::endl << message << std::endl;
#endif
    getchar(); // system("pause"); is windows only, don't use that!
    return 0;
}

备注：

如果您是 c++ 新手，请尽量避免使用 using namespace std; 并习惯 std:: 前缀
Why is "using namespace std;" considered bad practice?
不要使用 system("pause");
system("pause"); - Why is it wrong?
如果仅用于布尔值，请不要为宏使用值。你可以使用 #ifdef DEBUG 如果你不想使用它就不要定义 DEBUG
std::isspace 可以替换你的 takeFirstNonSpaceCharacter 函数
将长行拆分为多行以提高可读性

当用户键入分隔符时停止 getline() 输入

Stop getline() input when user types delimiter character

c++

input

getline