错误LNK2019：解析外部符号

#include <iostream> 
using namespace std; 

class A { 
public: 
    void function(int num); 
    bool function1()const; 
    virtual bool function2() const=0; 
}; 

class B:public A { 
public : 
    bool function2()const; 
}; 

int _tmain(int argc, _TCHAR* argv[]) 
{ 
    void (A::* p)(int)= &A::function; //不是地址，而是一个指向成员函数的指针 
    // Edit: Google translation of the above comment is 
    // "Not address, but a pointer to a member function pointer" 

    bool (A::* p1)()const =&A::function1; // 指向成员函数的指针可以指向一个常量成员函数 
    // Edit: Google translation of the above comment is 
    // "Point to a member function pointer can point to a const member function" 

    B b; 
    A *a=&b; 
    (a->*p1)(); 
    (b.*p1)(); 

    return 0; 
}

但是当我将其链接：错误LNK2019：解析外部符号

1>c.obj : error LNK2019: unresolved external symbol "public: bool __thiscall A::function1(void)const " ([email protected]@@QBE_NXZ) referenced in function _wmain 
1>c.obj : error LNK2019: unresolved external symbol "public: void __thiscall A::function(int)" ([email protected]@@[email protected]) referenced in function _wmain 
1>c.obj : error LNK2001: unresolved external symbol "public: virtual bool __thiscall B::function2(void)const " ([email protected]@@UBE_NXZ)

你能告诉我为什么吗？

来源

2012-03-25 Rollen Holt

你正在编码没有缩进。这很难阅读。 – kev 2012-03-25 04:49:31

我使用'astyle'缩进了代码。我也使用Google翻译了这些评论，但他们似乎与这个问题无关。 – 2012-03-25 04:58:50