代码不编译

Question

//cstack.h 
# ifndef _STACK_H__ 
#define _STACK_H__ 

#include<iostream> 
#include<vector> 

template< class Type ,int Size = 3> 
class cStack 
{ 
Type *m_array; 
int m_Top; 
int m_Size; 

public: 
    cStack(); 
    cStack(const Type&); 
    cStack(const cStack<Type,Size> &); 
    int GetTop()const; 
    bool Is_Full()const; 
    bool Is_Empty()const; 
    void InsertValue(const Type&); 
    void RemeoveValue(); 
    void show(); 
    ~cStack(); 
    friend std::ostream& operator <<(std::ostream &, const cStack<Type,Size> &); 
}; 

// iam writing only one function defination because linking is because of this function 
template< class Type,int Size > 
std::ostream& operator << (std::ostream &os, const cStack<Type,Size> &s) 
{ 
for(int i=0; i<=s.GetTop();i++) 
{ 
    os << s.m_array[i]; 
} 
return os; 
} 

 

//main.cpp 
#include "cStack.h" 
#include <string> 
#include<iostream> 

int main() 
{ 
cStack<int> sobj(1); 
std::cout << sobj; 
} 

我编译时出现以下错误：

error LNK2019: unresolved external symbol "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl operator<<(class std::basic_ostream<char,struct std::char_traits<char> > &,class cStack<int,3> const &)" (??6@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@std@@AAV01@ABV?$cStack@H$02@@@Z) referenced in function _main 

Answer 1

它编译，它只是不链接。 （我知道，这不是一个很大的帮助。）你没有一个地方正在实例化函数模板。你有一个main（）的地方试图使用这个流插入操作符吗？

Answer 2

我认为链接器找不到你的函数。将所有代码放在头文件中。

Answer 3

35.16Why do I get linker errors when I use template friends?

friend std::ostream& operator<< (std::ostream &, const cStack<Type, Size> &); 

标记功能模板功能

friend std::ostream& operator<< <>(std::ostream &, const cStack<Type, Size> &); 

，编译器会很高兴。 并将该函数定义放在类定义之前。

template< class Type ,int Size> 
class cStack; 

template< class Type ,int Size > 
std::ostream& operator <<(std::ostream &os, const cStack<Type,Size> &s) 
{ 
    for(int i=0; i<=s.GetTop();i++) 
    { 
     os << s.m_array[i]; 
    } 
    return os; 
} 


template< class Type ,int Size = 3> 
class cStack 
{ 
    Type *m_array; 
    int m_Top; 
    int m_Size; 
public: 
    cStack() {} 
    //... 
    friend std::ostream& operator<< <>(std::ostream &, const cStack<Type, Size> &); 
}; 

Answer 4

[剪断]

在Windows下面的工作与Visual Studio 2005

template <class Type, int Size = 3 > 
class cStack 
{ 
    // .... 

    template<class Type> 
    friend std::ostream& operator<< (std::ostream & os, const cStack<Type> &s); 
}; 

template<class Type> 
std::ostream& operator << (std::ostream &os, const cStack<Type> &s) 
{ 
    for(int i=0; i < s.GetTop();i++) 
    { 
     os << s.m_array[i]; 
    } 
    return os; 
}