I trying to learn the visitor pattern. So I am trying to implement a rather simple
and stupid example, so no need to point that out. Instead of separating the
classes into different file, its rather a small class so I just put everything
into one file. Here is the main.cpp :
#include <iostream>
#include "Print.h"
using namespace Print; //template print functions
using namespace std;
class PrintVisitor;
class Char;
class Integer;
class Float;
struct VisitElem;
struct VisitElem {
virtual void visit(const PrintVisitor& pv)const = 0;
};
class Char : public VisitElem{
char ch;
public:
Char(): ch(0){}
Char(char c) : ch(c){}
char elem(){ return ch; }
void visit(const PrintVisitor& pv)const{ pv.visit(*this); }
};
class Integer{
int i;
public:
Integer() : i(0){}
Integer(int in) : i(in){}
int elem(){ return i; }
void visit(const PrintVisitor& pv)const{ pv.visit(*this); }
};
class Float{
float fl;
public:
Float() : fl(0.0f){}
Float(float f) : fl(f){};
float elem(){ return fl; }
void visit(const PrintVisitor& pv)const{ pv.visit(*this); }
};
class PrintVisitor{
void visit(Char ch)const{ print(ch.elem());}
void visit(Integer i)const{ print(i.elem());}
void visit(Float fl)const{ print(fl.elem());}
};
int main()
{
return 0;
}
It gives me some errors because of the visit(...) method for each class. Here is the errors :
error C2027: use of undefined type 'PrintVisitor'
error C2228: left of '.visit' must have class/struct/union
I see why the error msg is. Its because the compiler does not know yet that
PrintVisitor has a visit method. But I am not sure how to solve this problem.
Any help is appreciated.
