如何在C++中调用全局函数中的类对象？

-3

我有一个全局函数void start_menu()，我用它作为接口。如何在C++中调用全局函数中的类对象？

void start_menu() 
{ 
    int x; 

    cout << " ------------------------------------" << endl; 
    cout << " WELCOME TO LIBRARY MANAGEMENT SYSTEM" << endl; 
    cout << "------------------------------------" << endl; 
    cout << "     1. ABOUT Books " << endl; 
    cout << "     2. ABOUT Members " << endl; 
    cout << "   CHOOSE:"; 
    cin >> x; 

    Books MyBooks; //object of books class 

    do 
    { 
     if (x==1) 
     { 
      system("cls"); 

      MyBooks.INTR_Books(); //calling function of Books Class  
     } 
    }; 
}

然后，我有class Books{}，我想在全局函数void start_menu()被调用，但是当我做Books类，它被定义为Books MyBooks;的对象，上面的代码给了我这个错误：

error: 'Books' was not declared in this scope.

这是后Books类全局函数void start_menu()：

class Books 
{ 
public: 
    string BookName; //name of the Book 
    string Auth; //Author of the book 
    string Trans; // translator of the book 
    string myArray[20]; 
    int BookCode; // code of the book 
    int BookNum; // number of copies exist 

    void INTR_Books(); //show interface related to books 
    void ADD_BOOK(); 
    void DELETE_BOOK(); 
    void SEARCH(); 
    void SHOW_ALL(); 
    void BR_BOOK(); 
};

来源

2017-06-13 moh89

在函数之前或之后是否声明了'Books'？ – NathanOliver

@NathanOliver，它也需要定义。 – Incomputable

@Incomputable是的，但可以来自后者或来自其他文件。 – NathanOliver

基于在评论中，我曾经在void start_menu()全局函数之后调用Books类。

来源

2017-06-13 13:04:42 moh89

如何在C++中调用全局函数中的类对象？

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