c++ - 验证数组 C++ 中的输入数据

Question

我有这个程序，我从中取出它:https://intcpp.tech-academy.co.uk/input-validation/它工作正常，我做了一些更改，因为我需要程序不断要求用户输入有效输入，所以为什么它在那里有 while 但是在第 4 次输入后它只询问 4 次输入将有效它不管它是否正确，有谁知道我该如何解决这个问题。谢谢

#include <iostream>
#include <string>
#include <cctype>

using namespace std;

int main () {

    cout << "Please enter name:" << endl;
    string userName;
    getline(cin, userName);

    bool rejected = false;

    while (rejected == false)
    {
        for (unsigned int i = 0; i < userName.length() && !rejected; i++)
        {

            if (isalpha(userName[i]))
                continue;

            else if (userName[i] == ' ')
                continue;

            else
            {
                cout << "Error, Please enter Patient's name again, First Name: ";
                getline(cin, userName);
                rejected = false;
            }

        }
        rejected = true;
    }

    system("pause");
    return 0;
}

Answer 1

我个人会做类似的事情

bool is_valid_username(std::string const& username)
{
    // First trim the string of all leading and trailing white-space
    trim(username);

    if (username.length() == 0)
        return false;  // Input was empty or all spaces

    return std::all_of(begin(username), end(username), [](char const ch)
    {
        return std::isalpha(ch) || ch == ' '; // Only letters and spaces are allowed
    });
}

std::string get_username()
{
    std::string username;

    do
    {
        std::cout << "Please enter username: ";
        std::getline(std::cin, username);
    } while (!is_valid_username(username));

    return username;
}

_{[关于trim 功能请see this old answer ]}

get_username 函数将在输入为空、全为空格或包含非字母或不包含空格的情况下永远继续请求用户名。

Here's a reference for std::all_of .

Here's a reference about lambda expressions .