c++ - 在切换情况下声明后，C++变量不会更改

Question

我仍在学习C++。我想编写一个默认值为O和X的代码。但是用户可以自己更改它，而两个值不能相同，也不能使用某些特殊符号。如果存在任何错误，则该值将重置为O和X。但是，在其中一种情况下重置该值之后，该变量仍包含错误值。希望我能从这里得到一些提示。这是我的代码。

int main()
{
    string s1 = "O";
    string s2 = "X";
    //User Interface
    cout << "***  Menu***" << endl;
    cout << "[1] " << endl;
    cout << "[2] " << endl;
    cout << "*****************" << endl;

    //Select Option
    string option; //For input
    int o; //For switch statement

    cout << "Option (1 - 2):";
    getline(cin, option);

    switch (o) {
    case 1: {
    } break;
    case 2: {
        cout << "[1] " << endl;
        cout << "[2] " << endl;
        ;
        cout << "Option (1 - 2):";
        string optionstring;
        getline(cin, optionstring);

        switch (optionstring[0]) {
        case '1': {
            break;
        }

        case '2': {
            cout << endl
                 << "current s1 =" << s1 << "Current s2 =" << s2 << endl
                 << endl;
            bool check = true;
            while (check) {
                check = false;
                string change; // For switch
                char c; // For switch statement

                cout << "Do you want to change the value? (Type Y to change or N to return to settings menu)?";

                getline(cin, change);
                if (change.size() > 1)
                    c = 'f'; //Indicates invalid input
                else
                    c = change[0];

                switch (c) {

                case 'Y':
                    cout << endl
                         << "Input new symbol for s1." << endl;

                    cout << "new symbol for s1:" << endl;
                    getline(cin, s1);
                    if (!(s1.size() == 1) || (s1 == "+") || (s1 == "-") || (s1 == "|")) {
                        string s1 = "O";
                        string s2 = "X";
                        cout << endl
                             << "The current setting has been reset to checker symbols‘" << s1 << "’for s1, ‘" << s2 << "’for s2)." << endl
                             << endl;
                        continue;
                    }
                    cout << endl
                         << "current s1 =" << s1;
                    break;
                }

当我在s1中输入“+”时，将显示一条错误消息，并且该值将重置为O，最后一行代码可以显示它已成功重置。但是在再次运行该案例之后，s1值仍然包含错误值，例如“+”。需要一些帮助!!

Answer 1

如果我对您的问题的解释正确，则应该可以进行以下操作。在这段代码中，您将创建新的临时变量s1和s2。

if (!(s1.size() == 1) || (s1 == "+") || (s1 == "-") || (s1 == "|")) {
                    string s1 = "O";
                    string s2 = "X";
                    ...

尝试避免声明新变量，如下所示:

    if (!(s1.size() == 1) || (s1 == "+") || (s1 == "-") || (s1 == "|")) {
                    s1 = "O";
                    s2 = "X";
                    ...