C ++模板，函数在类中定义？

Question

Class.h

template<class T>
  struct AStruct
  {
     //stuff
  };

class aClass
{
  template<class T>
  void setStruct(const AStruct<T>& s)
  {
    theStruct = s; 
  }

private:
  template<class T>
  AStruct<T> theStruct;  //this is not liked.  "multiple template parameter lists are not allowed" are one of the errors I get... 
}; 

Quite the mess but still, I'd like to know what can be done about it... I've tried playing around a bit but with no luck... Also, only standard library please!

Answer 1

template<class T>
struct AStruct{
};

template<class T>         //<-- the template must be here
class aClass {
public:
    void setStruct(const AStruct<T>& s){
         theStruct = s; 
    }
private:
    AStruct<T> theStruct; //<-- To construct this variable
};

Answer 2

Remove the template<class T>

template<class T>
struct AStruct{
 //stuff
};

template<class T>
class aClass{

 void setStruct(const AStruct<T>& s){
  theStruct = s; 
}

private:
AStruct<T> theStruct;   
}; 

You already defined AStruct to be a template

Answer 3

If you are holding a member that is a class template, then you either need a class template, or you need to provide a type for the template parameter. It seems like you need the former:

template<class T>
class aClass
{
  void setStruct(const AStruct<T>& s){
   theStruct = s; 
  }

private:
  AStruct<T> theStruct; // data member is class template
};