Classes, inheritance and over-riding

I've C knowledge, but newish to C++. I am trying to learn Orge 3D, which heavily uses OOP.

Can anyone explain the constructor of the following class?

Code:

class CameraTrackListener: public ExampleFrameListener
{
protected:
public:
    CameraTrackListener(RenderWindow* win, Camera* cam)
        : ExampleFrameListener(win, cam)
    {
    }

    bool frameStarted(const FrameEvent& evt)
    {

        mAnimState->addTime(evt.timeSinceLastFrame);

        // Call default
        return ExampleFrameListener::frameStarted(evt);
        

    }
};

Run this code and see what happens:

Code:

class A
{
public:
    A(int n) {cout << "A constructor - " << n << endl;}
};

class B : public A
{
public:
    B(int n) : A(n) {cout << "B constructor - " << n << endl;}
};

int main()
{
   B b(5);

   return 0;
}

Then, get yourself a good C++ book. You're halfway there if you already know C.

gg

Cheers dude, can you recommend a book?

I've read the tutorials on this site, but they didn;t address this particular question

Originally posted by charliemouse
I've C knowledge, but newish to C++. I am trying to learn Orge 3D, which heavily uses OOP.

Can anyone explain the constructor of the following class?

Code:

class CameraTrackListener: public ExampleFrameListener
{
protected:
public:
    CameraTrackListener(RenderWindow* win, Camera* cam)
        : ExampleFrameListener(win, cam)
    {
    }

    bool frameStarted(const FrameEvent& evt)
    {

        mAnimState->addTime(evt.timeSinceLastFrame);

        // Call default
        return ExampleFrameListener::frameStarted(evt);
        

    }
};

The constructor of CameraTrackListener is calling a constructor of
ExampleFrameListener (which is a base class that has its own
constructors) in its initialization stage... I'm thinking, anyway.

Cheers, I got constructors sorted.

Next, I thought functions from parent classes got inhirited?

If so, can somebody correct the following code snipit please

Code:

#include <iostream.h>

class mploygon
{
   public:
   mploygon ()
   {
   }
   mploygon(int a, int b)
   {
      cout << "Total = " << a + b << endl;
   }

   bool Area(int a, int b)
   {
      cout << "Area = " << a * b << endl;
      return (1);
   }
};

class mTriangle : mploygon
{
   public:
   mTriangle(int a, int b) : mploygon (a,b)
   {
      cout << "This is the triangle constructor" << endl;
   }
};

int main()
{
   mTriangle * b = new mTriangle(5,5);
   b->Area(5,5);

   return(0);
}

The dodgy line is ;

Code:

b->Area(5,5);

class mTriangle : mploygon

this means

class mTriangle : private mploygon

This means is implemented in terms of. It does not imply in any way that a mTriangle IS A mploygon.

btw polygon is spelt like that and not ploygon.

• "mploygon" => "mPolygon"? mVarName is usually used for hungarian notation for a member variable, not class name
• "class mTriangle : mploygon" == "class mTriangle : private mploygon" - which means you can't access mploygon members through an instance of mTriangle.
• "mTriangle * b = new mTriangle(5,5);" - You better delete that!!

Cheers dudes.

As you can tell i'm a serious noobie, but this is a very friendly forum!!!

Dont use any form f hungarian notation because it is counterintuitive. It actually makes for less readable code. Common practice these days to distinguish member vars from nonmember vars is that member vars have either prepended or appended an underscore('_'). More and more these days we see this appended and not prepended because the compiler reserves many underscore-prepended names for its own use.