C++錯誤LNK2019：無法解析的外部符號_main在函數中引用_tmainCRTStartup

Question

我是一個完整的初學C++。我試圖調試我的代碼，因爲我確定有一些指針錯誤，並且我仍然試圖理解，但我無法編譯它。該代碼最初來自我編寫的java程序，它只是一個帶有一些比較方法的歌類，我已將它轉錄爲C++以嘗試瞭解這些語言之間的差異，代碼本身沒有顯示錯誤，但它不能編譯沒有彈出錯誤。我試着尋找解決這個錯誤的方法，但沒有發現任何作用，所以這裏是我的代碼爲win32控制檯項目。感謝您的幫助。

 // ConsoleApplication4.cpp : Defines the entry point for the console application. 
// 

#include "stdafx.h" 
#include <string> 
#include <iostream> 

using namespace std; 

class Song { 
private: 
    string Artist; 
    string Title; 
    string Lyrics; 
public: 
    static int Sortcount; 
    static int Searchcount; 

    Song(string A_Artist, string T_Title, string L_Lyrics) { 

     Artist = A_Artist; 
     Title = T_Title; 
     Lyrics = L_Lyrics; 
    } 

    //Compares the artist of one song to another. 
    class ArtistComparator { 

    public: 
     int compare(Song *o1, Song *o2) { 
      string Artist1 = (*o1).Artist; 
      string Artist2 = (*o2).Artist; 
      Searchcount++; 

      if (Artist1.compare(Artist2) == 0){ 
       return 0; 
      } 
      Searchcount++; 
      return (*o1).Artist.compare((*o2).Artist); 
     } 

    }; 

    //Compares the title of one song to another. 
    class TitleComparator { 

    public: 

     int compare(Song arg0, Song arg1) { 

      string Title1 = arg0.Title; 
      string Title2 = arg1.Title; 
      return Title1.compare(Title2); 
     } 
    }; 


public: 

    //Testing method to make sure the Song class works and 
    //the compareTo method works. 
    int main(int argc, char** argv){ 
     Song test1 = Song("cat", "bat", "this is not a real song"); 
     Song test2 = Song("cat", "apple", "also not a real song"); 
     int compareResult = test1.compareTo(test2); 
     if (compareResult == -1){ 
      std::cout << "test1 comes first"; 
     } 
     else{ 
      cout << "test2 comes first"; 
      cout << test2.toString(); 
     } 

    }; 

    string getArtist(){ 
     return Artist; 
    }; 

    string getTitle(){ 
     return Title; 
    }; 

    string getLyrics(){ 
     return Lyrics; 
    }; 

    string toString(){ 
     return Artist + ", " + Title + ", " + Lyrics; 
    }; 

    //compareTo method used for sorting songs. 
    //increments Sortcount each time it is called to keep track 
    //of the efficiency of the sort algorithm. 
private: 
    int compareTo(Song other){ 
     Sortcount++; 
     int art = Artist.compare(other.Artist); 
     if (art == 0){ 

      return Title.compare(other.Title); 
     } 
     else 
      return art; 
    } 
}; 

Answer 1

#include "stdafx.h" 
#include <string> 
#include <iostream> 

using namespace std; 

class Song { 
private: 
    string Artist; 
    string Title; 
    string Lyrics; 
public: 
    int Sortcount; 
    static int Searchcount; 

    Song(string A_Artist, string T_Title, string L_Lyrics) { 

     Artist = A_Artist; 
     Title = T_Title; 
     Lyrics = L_Lyrics; 
    } 

    //Compares the artist of one song to another. 
    class ArtistComparator { 

    public: 
     int compare(Song *o1, Song *o2) { 
      string Artist1 = (*o1).Artist; 
      string Artist2 = (*o2).Artist; 
      Searchcount++; 

      if (Artist1.compare(Artist2) == 0){ 
       return 0; 
      } 
      Searchcount++; 
      return (*o1).Artist.compare((*o2).Artist); 
     } 

    }; 

    //Compares the title of one song to another. 
    class TitleComparator { 

    public: 

     int compare(Song arg0, Song arg1) { 

      string Title1 = arg0.Title; 
      string Title2 = arg1.Title; 
      return Title1.compare(Title2); 
     } 
    }; 


public: 

    //Testing method to make sure the Song class works and 
    //the compareTo method works. 


    string getArtist(){ 
     return Artist; 
    }; 

    string getTitle(){ 
     return Title; 
    }; 

    string getLyrics(){ 
     return Lyrics; 
    }; 

    string toString(){ 
     return Artist + ", " + Title + ", " + Lyrics; 
    }; 

    //compareTo method used for sorting songs. 
    //increments Sortcount each time it is called to keep track 
    //of the efficiency of the sort algorithm. 
    int compareTo(Song other){ 
     Sortcount++; 
     int art = Artist.compare(other.Artist); 
     if (art == 0){ 

      return Title.compare(other.Title); 
     } 
     else 
      return art; 
    } 
}; 

int main(int argc, char** argv){ 
    Song test1 = Song("cat", "bat", "this is not a real song"); 
    Song test2 = Song("cat", "apple", "also not a real song"); 
    int compareResult = test1.compareTo(test2); 
    if (compareResult == -1){ 
     std::cout << "test1 comes first"; 
    } 
    else{ 
     cout << "test2 comes first"; 
     cout << test2.toString(); 
    } 
    getchar(); 
    return 0; 
} 

變化做：

1. 感動main()類
2. 製造compareTo()功能public，因爲它是直接叫
3. 刪除static從int Sortcount，因爲我無法更新外沒有這個變量。