c ++類中的指針數組

Question

我想要一個類中的指針數組。 這是我嘗試的代碼。 但是我得到一個錯誤。

class Msg{
    public:
      char *msg[2]={
                   "one",
                   "two",
                    "three"
                 };

//there are some other methods I want to write.....
 };


void main(){
     Msg msg;
//  i want to print msg[] here using a for loop
}

但是它不能編譯，並且在類中顯示錯誤，我也想知道如何訪問屬於類成員的指針數組。 如果我輸入錯誤，請更正語法。

edit:[i want to do]

我有大約12條固定消息，這些消息根據情況顯示，我設置了一個枚舉來獲取正確的索引。

enum{
    size,
    area,
    volume,
    //etc 

};

class Msg有一個函數putMsg(int index)其中cout需要MSG當我通過一個枚舉。 如果我通過area ，它將放一個味精，例如“根據您的等式計算的面積為：”，是否有更好的方法來進行此類消息傳遞。

Answer 1

嘗試這個：

class Msg{
    public:

      // Can not initialize objects in the declaration part.
      // So just provide the declaration part.
      static char const *msg[];

      // Note: You had the completely wrong size for the array.
      //       Best to leave the size blank and let the compiler deduce it.

      // Note: The type of a string literal is 'char const*`

      // Note: I have made it static so there is only one copy.
      //       Since the strings are literals this should not affect usage
      //       But if you wanted one per class you need another technique.


    //there are some other method i want to write.....
};

// Now we can provide a definition.
// Note: I still leave the size blank and let the compiler deduce the size.
      char const* Msg::msg[]={
                   "one",
                   "two",
                    "three"
                 };  


// Note: main() must return an int.    
int  main(){
     Msg msg;
//  i want to print msg[] here using a for loop


    // The basic way
    for(std::size_t loop = 0;loop < sizeof(Msg::msg)/sizeof(Msg::msg[0]); ++loop)
    {
        std::cout << Msg::msg[loop] << "\n";
    }

    // Same as above but using C++11
    for(auto loop = std::begin(Msg::msg); loop != std::end(Msg::msg);++loop)
    {
        std::cout << *loop << "\n";
    }

    // using algorithms:
    std::copy(std::begin(Msg::msg), std::end(Msg::msg), std::ostream_iterator<char *const>(std::cout, "\n"));



     // Note: You don't actually need a return statement in main().
     //       If you don't explicitly provide one then 0 is returned.

}

Answer 2

這與它是一個指針數組（BTW並不是特別好用，請考慮使用std::vector<std::string> ）無關，但是與您嘗試初始化msg的方式msg 。 這是一個（非靜態）成員變量，因此您必須在類的構造函數中初始化它，而不是在聲明它的地方初始化它。

class Msg{
    public:
      char *msg[3];

      Msg()
        : msg{ "one"
             , "two"
             , "three" }
      {}

//there are some other method i want to write.....
 };

Answer 3

我懷疑，但我不能肯定地說（您尚未發布實際錯誤），您會收到“初始化程序錯誤太多”的信息 。

將*msg[2]更改為*msg[3] 。 或將其保留為空白。 []

或刪除“三個”。