我似乎无法获得Visual C++ Express（2010）识别枚举类

Question

嗨，大家好（和女孩）， 我正在努力重新熟悉C++后，只使用Python太久。我已经用MS Visual C++ 2010 Express版编写了一个小程序，并且我已经遍地查找了为什么编译器似乎不喜欢使用enum类Choice的罪魁祸首。编译器抱怨这个名字的命名空间不存在。现在，我应该说我写的所有以前的C/C++代码都在学术环境中，因此我使用了完整的IDE。无论如何，我附上下面的代码，请原谅我，如果这是不正确的方法发布它。如果是这样，请参考我的正确方法，我将在今后使用它。提前感谢您提供任何帮助或洞见任何人可能能够借出。代码如下。

#include"stdafx.h" 
#include<iostream> 
#include<string> 
#include<ctime> 
using namespace std; 

enum class Choice { rock, paper, scissors }; 
using namespace Choice;** 

Choice player_choice; //holds user's move 
Choice machine_choice; //holds machine's move 

string words[3] = {"rock","paper","scissors"}; 

Choice get_machine_choice(); 
void decide_winner(); 
string get_msg(Choice winner); 
int rand0toN1(int n); 
int main(int argc, char *argv[]) 
{ 
    srand(time(NULL)); //set randomization 
    string input_str; 
    int c; 
    while (true) { 
     cout << "Enter Rock, Paper, Scissors, or Exit: "; 
     getline(cin, input_str); 
     if (input_str.size() < 1) { 
      cout << "Sorry, I don't understand that.\n"; 
      continue; 
     } 
     c = input_str[0]; 
     if (c == 'R' || c == 'r') 
      player_choice = rock; 
     else if (c == 'P' || c == 'p') 
      player_choice = paper; 
     else if (c == 'S' || c == 's') 
      player_choice = scissors; 
     else if (c == 'E' || c == 'e') 
      break; 
     else { 
      cout << "Sorry, I don't understand that.\n"; 
      continue; 
     } 
     machine_choice = get_machine_choice(); 
     int p = (int) player_choice; 
     int c = (int) machine_choice; 
     cout << "You Choose " << words [p]; 
     cout << "," << endl; 
     cout << "I choose " << words [c]; 
     cout << "," << endl; 
     decide_winner(); 
    } 
    return EXIT_SUCCESS; 
} 

Choice get_machine_choice() { 
    int n = rand0toN1(3); 
    if (n == 0) return rock; 
    if (n == 1) return paper; 
    return scissors; 
} 

void decide_winner() { 
    if (player_choice == machine_choice) { 
     cout << "Reult is a tie.\n\n"; 
     return; 
    } 
    int p = static_cast<int>(player_choice); 
    int c = static_cast<int>(machine_choice); 
    if (p - c == 1 || p - c == -2) { 
     cout << get_msg(player_choice); 
     cout << "Unfortunantly, you win...\n"; 
    } else { 
     cout << get_msg(machine_choice); 
     cout << "I WIN, BEEEATCH!!!!\n"; 
    } 
    cout << endl; 
} 

string get_msg(Choice winner) { 
    if (winner == rock) 
     return string("Rock smashes scissors, beeatch..."); 
    else if (winner == paper) 
     return string("You know what paper does to rock, COVERAGE!!..."); 
    else 
     return string("CHOP! Scissors cut paper!!...."); 
} 

int rand0toN1(int n) { 
    return rand() % n; 
} 

再次感谢您花时间帮助我。我似乎记得经常使用C++来声明类，并且不知道为什么它不会识别它。再次感谢您抽出时间。法院（南卡罗来纳州克莱姆森大学）

Answer 1

VC++在2010年不支持枚举类。您需要2012。

Answer 2

enum class在visual C++ 2010中不受支持，但我认为它在vC++ 2012中。 请参阅here。

你将不得不升级你的编译器或者使用普通的“enum”，当然它的工作原理略有不同。

Answer 3

所以它看起来像你想使用名称空间“选择”，但你没有先定义它。 要定义一个新的命名空间，定义它像：

namespace X { // namespace definition 
    int a; 
    int b; 
    } 
using namespace X; //then you can use it 

但事实上，我不知道你需要定义任何命名空间... 在你的情况，我找出的问题是，你声明“枚举类选择“，而不仅仅是”枚举选择“。请C++例如读取有关枚举使用此链接：http://www.cplusplus.com/forum/beginner/44859/

我修改你的代码这种方式，它运行良好：

#include"stdafx.h" 
#include<iostream> 
#include<string> 
#include<ctime> 
using namespace std; 

enum Choice { 
     rock, 
     paper, 
     scissors }; 

Choice player_choice; //holds user's move 
Choice machine_choice; //holds machine's move 

string words[3] = {"rock","paper","scissors"}; 

Choice get_machine_choice(); 
void decide_winner(); 
string get_msg(Choice winner); 
int rand0toN1(int n); 

int main(int argc, char *argv[]) 
{ 
    srand(time(NULL)); //set randomization 
    string input_str; 
    int c; 
    while (true) { 
     cout << "Enter Rock, Paper, Scissors, or Exit: "; 
     getline(cin, input_str); 
     if (input_str.size() < 1) { 
      cout << "Sorry, I don't understand that.\n"; 
      continue; 
     } 
     c = input_str[0]; 
     if (c == 'R' || c == 'r') 
      player_choice = rock; 
     else if (c == 'P' || c == 'p') 
      player_choice = paper; 
     else if (c == 'S' || c == 's') 
      player_choice = scissors; 
     else if (c == 'E' || c == 'e') 
      break; 
     else { 
      cout << "Sorry, I don't understand that.\n"; 
      continue; 
     } 
     machine_choice = get_machine_choice(); 
     int p = (int) player_choice; 
     int c = (int) machine_choice; 
     cout << "You Choose " << words [p]; 
     cout << "," << endl; 
     cout << "I choose " << words [c]; 
     cout << "," << endl; 
     decide_winner(); 
    } 
    return EXIT_SUCCESS; 
} 

Choice get_machine_choice() { 
    int n = rand0toN1(3); 
    if (n == 0) return rock; 
    if (n == 1) return paper; 
    return scissors; 
} 

void decide_winner() { 
    if (player_choice == machine_choice) { 
     cout << "Reult is a tie.\n\n"; 
     return; 
    } 
    int p = static_cast<int>(player_choice); 
    int c = static_cast<int>(machine_choice); 
    if (p - c == 1 || p - c == -2) { 
     cout << get_msg(player_choice); 
     cout << "Unfortunantly, you win...\n"; 
    } else { 
     cout << get_msg(machine_choice); 
     cout << "I WIN, BEEEATCH!!!!\n"; 
    } 
    cout << endl; 
} 

string get_msg(Choice winner) { 
    if (winner == rock) 
     return string("Rock smashes scissors, beeatch..."); 
    else if (winner == paper) 
     return string("You know what paper does to rock, COVERAGE!!..."); 
    else 
     return string("CHOP! Scissors cut paper!!...."); 
} 

int rand0toN1(int n) { 
    return rand() % n; 
} 

Answer 4

枚举类是介绍为C++ 11标准的一部分。它不会存在于VC2010中。 您需要升级到VC2012才能使用此功能。否则，从枚举声明中删除“class”。

enum class Choice { rock, paper, scissors }; //Error in vs2010. Drop class. 
enum class Choice { rock, paper, scissors }; //Ok in vs2012. 
enum Choice { rock, paper, scissors }; //Ok in vs2010.