类模板的友元 | marstau's blog

1，根据情况2，绑定模板友元函数。\ template\<class T\>\ class CTest;\ template \<class T\>\ ostream & operator\<\<(ostream &os,const CTest\<T\>& rhs);\ template\<class T\>\ class CTest\ {\ public:\ CTest(const T& val): \_item(val){}\ \~CTest(void){}\ friend ostream & operator\<\< \<T\>(ostream & os,const CTest\<T\>&rhs); // care \<T\>\ private:\ T \_item;\ };\ template \<class T\>\ ostream & operator\<\<(ostream &os,const CTest\<T\>& rhs)\ {\ os\<\<"this is CTest:"\<\<rhs.\_item\<\<endl;\ return os;\ }\ 2.根据情况3，用非绑定形式的模板函数\ template\<class T\>\ class CTest\ {\ public:\ CTest(const T& val): \_item(val){}\ \~Ctest(void){}\ template\<class U\>\ friend ostream & operator\<\<(ostream & os,const CTest\<U\>&rhs);\ private:\ T \_item;\ };\ template \<class T\>\ ostream & operator\<\<(ostream &os,const CTest\<T\>& rhs)\ {\ os\<\<"this is CTest:"\<\<rhs.\_item\<\<endl;\ return os;\ }\ 上面两种改法都在gcc上面编译通过

// 另一个实例

//-----------------------------------------\ template\<class Type\>\ class Matrix; // 友元类forward declaration\ template\<class Type\>\ ostream &operator \<\< ( ostream &os, Matrix\<Type\> &m ); \ template\<class Type\>\ Matrix\<Type\> &operator + ( Matrix\<Type\> &m1, Matrix\<Type\> &m2 );\ //-----------------------------------------\ template\<class elemType = int\>\ class element{\ public:\ // ![](http://www.cppblog.com/Images/dot.gif).\ friend class Matrix\<elemType\>;\ friend Matrix\<elemType\> &operator + \<elemType\>( Matrix\<elemType\> &m1, Matrix\<elemType\> &m2 );// care \<elemType\>， the same as follows\ friend ostream &operator \<\< \<elemType\>( ostream &os, Matrix\<elemType\> &m ); \ };\ //======================================================================\ template\<class Type\>\ istream &operator \>\> ( istream &is, Matrix\<Type\> &m );\ template\<class Type\>\ class Matrix{\ public:\ //![](http://www.cppblog.com/Images/dot.gif).\ friend Matrix\<Type\> &operator + \<Type\>( Matrix\<Type\> &m1, Matrix\<Type\> &m2 );\ friend ostream &operator \<\< \<Type\>( ostream &os, Matrix &m );\ friend istream &operator \>\> \<Type\>( istream &is, Matrix &m );\ };\ template\<class Type\>\ Matrix\<Type\> &\ operator + ( Matrix\<Type\> &m1, Matrix\<Type\> &m2 ){\ // 定义\ }\ template\<class Type\>\ ostream &\ operator \<\< ( ostream &os, Matrix\<Type\> &m ){\ // 定义\ }\ template\<class Type\>\ istream &operator \>\> ( istream &is, Matrix\<Type\> &m ){\ // 定义\ }

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