在C++中，如何引用不同頭文件中的函數？

Question

我正在嘗試創建一個簡單的文本冒險，並且將代碼拆分爲多個頭文件，以使編譯時間更快並使其更加有組織。

//main.cpp 
#include <iostream> 
#include <fstream> 
#include "main_menu.h" 
#include "file_select.h" 
using namespace std; 
int main() 
{ 
main_menu(); 
} 

主菜單頭文件看起來是這樣的：

\\main_menu.h 
#ifndef main_menu_H 
#define main_menu_H 
#include <iostream> 
#include "file_select.h" 
using namespace std; 
void main_menu() { 
cout << string(50,'\n'); 
cout << "      ADVENTURE OF THE SKYLANDS         \n"; 
cout << "================================================================================\n"; 
cout << "        CHAPTER 1           \n"; 
cout << "================================================================================\n"; 
cout << "       Scepter of The Winds         \n"; 
cout << "        v1.0.0           \n"; 
cout << "================================================================================\n"; 
char select; 
cout << "\n\n\n\n\n" << "MAIN MENU\n\n"; 
cout << "1. Start\n"; 
cout << "2. File Select\n"; 
cout << "3. Credits\n"; 
cout << "4. Exit Game\n"; 
cin >> select; 
if (select == 'S' || select == 's' || select == '1') { 

} 
else if (select == 'F' || select == 'f' || select == '2') { 
    file_select(); 
} 
else if (select == 'C' || select == 'c' || select == '3') { 
} 
else if (select == 'E' || select == 'e' || select == 'x' || select == 'X' || select == '4') { 
    return; 
    } 
    else { 
     cout << "Invalid Option!"; 
    } 
} 
#endif 
#include 

最後，文件選擇菜單的頭文件，這就是我有一個錯誤：「MAIN_MENU」並沒有在此聲明範圍。

#ifndef file_select_H 
#define file_select_H 
#include <iostream> 
#include "main_menu.h" 
using namespace std; 
void file_select() { 
cout << "      FILE SELECT            \n"; 
cout << "==================================================================================\n"; 
cout << "1. File 1\n"; 
cout << "2. File 2\n"; 
cout << "3. File 3\n"; 
cout << "4. Return to Main Menu\n"; 
char fileselect; 
cin >> fileselect; 
if (fileselect == '1') { 
} 
else if (fileselect == '2') { 
} 
else if (fileselect == '3') { 
} 
else if (fileselect == '4') { 
main_menu(); 
} 
else { 
    cout << "Invalid Option."; 
} 
} 

#endif 

Answer 1

一般來說，頭文件應該只包含聲明而CPP文件應包含定義的聲明。這意味着對於任何聲明，只提供返回類型，函數名稱和任何參數類型，後跟分號。該定義要求您提供聲明中的所有內容，還需要提供參數名稱和所有要進入函數的語句。實例爲以下：

宣言實施例（頭文件）：

• void file_select();
• void main_menu();
• int anotherExample(int);
• bool finalExample(char optionalVariableName);

的Defi nition實例（CPP文件）：

bool finalExample(char optionalVariableName) { 
    return (optionalVariableName == '\0'); 
} 

話雖這麼說，你的代碼應該轉化爲以下幾點：

main.cpp

#include "MainMenu.h" 

using namespace std; 

int main() { 
    main_menu(); 
    return 1; 
} 

MainMenu.h

#ifndef MAIN_MENU_H 
#define MAIN_MENU_H 

#ifndef FILE_SELECT_H 
#include "FileSelect.h" 
#endif 

void main_menu(); 

#endif 

MainMenu.cpp

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

using namespace std; 

void main_menu() { 
    cout << string(50,'\n'); 
    cout << "      ADVENTURE OF THE SKYLANDS         \n"; 
    cout << "================================================================================\n"; 
    cout << "        CHAPTER 1           \n"; 
    cout << "================================================================================\n"; 
    cout << "       Scepter of The Winds         \n"; 
    cout << "        v1.0.0           \n"; 
    cout << "================================================================================\n"; 
    char select; 
    cout << "\n\n\n\n\n" << "MAIN MENU\n\n"; 
    cout << "1. Start\n"; 
    cout << "2. File Select\n"; 
    cout << "3. Credits\n"; 
    cout << "4. Exit Game\n"; 
    cin >> select; 
    if (select == 'S' || select == 's' || select == '1') { 

    } 
    else if (select == 'F' || select == 'f' || select == '2') { 
     file_select(); 
    } 
    else if (select == 'C' || select == 'c' || select == '3') { 
    } 
    else if (select == 'E' || select == 'e' || select == 'x' || select == 'X' || select == '4') { 
     return; 
    } 
    else { 
     cout << "Invalid Option!"; 
    } 
} 

FileSelect.h

#ifndef FILE_SELECT_H 
#define FILE_SELECT_H 

#ifndef MAIN_MENU_H 
#include "MainMenu.h" 
#endif 

void file_select(); 

#endif 

FileSelect.cpp

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

using namespace std; 

void file_select() { 
    cout << "      FILE SELECT            \n"; 
    cout << "==================================================================================\n"; 
    cout << "1. File 1\n"; 
    cout << "2. File 2\n"; 
    cout << "3. File 3\n"; 
    cout << "4. Return to Main Menu\n"; 
    char fileselect; 
    cin >> fileselect; 
    if (fileselect == '1') { 
    } 
    else if (fileselect == '2') { 
    } 
    else if (fileselect == '3') { 
    } 
    else if (fileselect == '4') { 
     main_menu(); 
    } 
    else { 
     cout << "Invalid Option."; 
    } 
}