使用 cin.get() 似乎无法读取我期望的字符。怎么了？

Question

所以我正在开发这个程序来执行基本任务的菜单，其中一项是判断用户输入的字符是大写字母、小写字母还是非字母。

#include <iostream>
using namespace std;

int main () {

    int mi;

    cout << "1) Area of Circle" << endl;
    cout << "2) Character Detection" << endl;
    cout << "3) Capitalization 1-3-5" << endl;
    cout << "4) Binomial Roots" << endl;
    cout << "0) Quit" << endl;

    cin >> mi;

    switch (mi) {
        case 2:
        {
            char c;
            cout << "input a character:  ";
            cin.get(c);
            cin.ignore(); /////// unsure if using this properly
            if ('a' <= c && c <= 'z') {cout << "c is lower case" << endl;}
            else if ('A' <= c && c <= 'Z') {cout << "C IS UPPER CASE" << endl;}
            else { cout << "C is not a letter" << endl;}
        }
            break;
    }


    return 0;
}

选择 2 并输入字母（或任何其他字符）后，输出始终为 "C is not a letter."
令我困惑的是，如果我将案例 2 中的内容放在一个单独的程序中，即

using namespace std;
int main () {
    char c;
    cout << "input a character:  ";
    cin.get(c);
    if ('a' <= c && 'z' >= c) {cout << "c is lower case" << endl;}
    else if ('A' <= c && c <= 'z') {cout << "C IS UPPER CASE" << endl;}
    else { cout << "C is not a letter" << endl;}
    return 0;
}

它完全按照预期的方式工作，我什至不需要 cin.ignore()，因为出于某种原因它只在 switch 语句中跳过用户输入部分。我在这里错过了什么？

Answer 1

我建议您使用 cin>> 而不是 cin.get() 因为 cin.get() 在每次初始化之后都会 "grab" 放入流中的换行符每次按回车。

#include <iostream>
using namespace std;

int main () {

int mi;

cout << "1) Area of Circle" << endl;
cout << "2) Character Detection" << endl;
cout << "3) Capitalization 1-3-5" << endl;
cout << "4) Binomial Roots" << endl;
cout << "0) Quit" << endl;

cin >> mi;

switch (mi) {
    case 2:
    {
        char c;
        cout << "input a character:  ";
        cin>>c;
        cin.ignore(); /////// unsure if using this properly
        if ('a' <= c && c <= 'z') {cout << "c is lower case" << endl;}
        else if ('A' <= c && c <= 'Z') {cout << "C IS UPPER CASE" << endl;}
        else { cout << "C is not a letter" << endl;}
    }
        break;
}


return 0;
}

使用 cin.get() 似乎无法读取我期望的字符。怎么了？

Using cin.get() doesn't seem to read the character I'm expecting. What's wrong?

c++

if-statement

cin

switch-statement