C++ 过载<&书信电报；模板类中的运算符为我提供链接器错误（C+；+；）

在您询问之前，是的，该函数在我的模板类的标题中定义

下面是

示例.h的相关位：

template<class T, class J, const int X, const int Y>
class Example {
    public:
        friend std::ostream& operator<<(std::ostream& s, const Example<T,J,X,Y>& b);
}

template<class T, class J, const int X, const int Y>
std::ostream& operator<<(std::ostream& s, const Example<T,J,X,Y>& b) {
    // stuff
}

编译时，我收到以下链接器错误：

Undefined symbols for architecture x86_64:
  "operator<<(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, Example<A, B, 5, 5> const&)", referenced from:
      foo(Example<A, B, 5, 5>&) in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [dist/Debug/GNU-MacOSX/consolehero] Error 1
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2

架构x86_64的未定义符号：
“操作员长话短说：

warning: friend declaration ‘std::ostream& operator<<
(std::ostream&, const Example<T, J, X, Y>&)’ declares a non-template function

或者，使用

template<class T, class J, const int X, const int Y>
class Example {
    public:
        template<class T1, class J1, const int X1, const int Y1>
        friend std::ostream& operator<<(std::ostream& s, 
                                         const Example<T1,J1,X1,Y1>& b);
};

template<class T1, class J1, const int X1, const int Y1>
std::ostream& operator<<(std::ostream& s, const Example<T1,J1,X1,Y1>& b) {
    // stuff
}

模板
课例{
公众：
模板
friend std:：ostream&operatorMan，这东西令人困惑。我是通过删除类中的定义来实现的。然后我在定义中添加了
inline
。它可以工作-但是如何工作？程序如何知道在调用
@maxmackie时使用该函数找到了一些文档，请参阅更新的编辑或模板（friend operators）
template<class T, class J, const int X, const int Y>
class Example {
    public:
        friend std::ostream& operator<<(std::ostream& s, const Example& b)
        { 
            // stuff here
        }
};

template<class T, class J, const int X, const int Y>
class Example {
    public:
        template<class T1, class J1, const int X1, const int Y1>
        friend std::ostream& operator<<(std::ostream& s, 
                                         const Example<T1,J1,X1,Y1>& b);
};

template<class T1, class J1, const int X1, const int Y1>
std::ostream& operator<<(std::ostream& s, const Example<T1,J1,X1,Y1>& b) {
    // stuff
}

friend std::ostream& operator<<(std::ostream& s, const Example& b){}

friend std::ostream& operator<<(std::ostream& s, const Example<T,J,X,Y>& b){}