c++ - 重载输入 (>>) 运算符以获取枚举字符串

Question

enum shuffle_mode {IN, OUT};
istream& operator>> (istream& in, shuffle_mode& shuffle) {
    int a;
    in >> a;
    if (a==1) {shuffle=IN;}
    if (a==2) {shuffle=OUT;}
}

我想修改这个运算符重载，以便它能够直接将 IN 或 OUT 作为输入，而不是枚举中的相应数字。

在一个完美的场景中，它看起来像这样:

istream& operator>> (istream& in, shuffle_mode shuffle) {
in >> shuffle;
}

Answer 1

你说

In a perfect scenario it would look something like this:

istream& operator>> (istream& in, shuffle_mode shuffle) {
  in >> shuffle;
}

那就麻烦了。这将导致无限递归和堆栈溢出。

您可以使用:

istream& operator>> (istream& in, shuffle_mode& shuffle) {
    std::string token;
    in >> token;
    if ( token == "IN" || token == "1" ){shuffle=IN;}
    else if ( token == "OUT" || token == "2" ){shuffle=OUT;}
    else { /* Error */ }

    return in;
}