CODEWITHSUNDEEP
c++inheritancevirtual
WinterGreen
WinterGreen

Reputation: 3

Problem implementing virtual method in derived class

Hey I was trying to multiple inherit a pure virtual function using MVS2010 Compiler. So I can run a draw for all renderable objects.

So here is the diagram

in ASCII

|Renderable            | |Entity             |
|virtual bool draw()=0;| | functions in here |

    is - a              is - a


                Shape

So it seems it wont let me inherit the pure virtual function? and implement the virtual function. Here is my code.

// Renderable.h
#ifndef H_RENDERABLE_
#define H_RENDERABLE_
class Renderable
{
 public:
    virtual bool Draw() = 0;
};
#endif


 //Shapes.h
 #ifndef H_SHAPES_
 #define H_SHAPES_
 #include "Renderable.h"
 #include "Entity.h"
 class Shapes : public Entity, public Renderable
 {
 public:
     Shapes();
     ~Shapes();

 };


 #endif

 //shapes.cpp
 #include "Shapes.h"


 Shapes::Shapes()
 {
 }


 Shapes::~Shapes()
 {
 }


 virtual void Shapes::Draw()
 {
 }

I have tried multiple things and it doesn't work also google searched.

Upvotes: 0

Views: 565

Answers (3)

ksming
ksming

Reputation: 1462

First, you need to declare the draw function again in your Shapes class. Then make sure it has the same signature as the one declared in the Renderable class.

//Shapes.h
 #ifndef H_SHAPES_
 #define H_SHAPES_
 #include "Renderable.h"
 #include "Entity.h"
 class Shapes : public Entity, public Renderable
 {
 public:
     Shapes();
     ~Shapes();

     virtual bool Draw();

 };


 #endif

 //shapes.cpp

bool Shapes::Draw()
{
}

Upvotes: 1

Vaughn Cato
Vaughn Cato

Reputation: 64308

You need to declare Draw in Shapes:

class Shapes : public Entity, public Renderable
{
  public:
    Shapes();
    ~Shapes();
    virtual void Draw(); 
};

Just defining it later is not enough.

Upvotes: 0

Björn Pollex
Björn Pollex

Reputation: 76778

Your return types are not matching. The Renderable::Draw returns bool, and you Shapes::Draw returns void. The entire function signature (including the return types) must match, otherwise the function in the derived class simply hides the function in the base class.

Upvotes: 0

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