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Hide or overwrite

Started by Ellal Nov 22, 2001 at 10:22 AM 1 replies 300+ views

Original Post

Nov 22, 2001 at 10:22 AM

What''s the difference between overwriting a base-class method(in a derived class), and hiding it? Elall "It''''s all about reading between the lines"

Fruny

Nov 22, 2001 at 11:12 AM

In C++ you declare that you want to override a method with the 'virtual' keyword. That means that, instead of calling the method that is in the parent class, all methods must call the method appropriate to the class of the object.

Here is an example :

    

class Base
{
  void Hidden() 
  { 
    cout << "Base::Hidden." << endl; 
  }
  virtual void Overriden() 
  { 
    cout << "Base::Overriden." << endl; 
  }
  void DoStuff()
  { 
    Hidden(); 
    Overriden(); 
  }
}

class Child : public Base
{
  void Hidden() 
  { 
    cout << "Child::Hidden." << endl; 
  }

  void Overriden() // already virtual from Base

  { 
    cout << "Child::Overriden." << endl; 
  }

  void DoMoreStuff()
  {
    Hidden();
    Overriden();
  }
}

.
.
.

Base B;
Child C;

B.DoStuff()
// prints out

// Base::Hidden

// Base::Overriden


C.DoStuff()
// prints out

// Base::Hidden

// Child::Overriden


C.DoMoreStuff()
// prints out

// Child::Hidden

// Child::Overriden

Edit: Fixed the typo the next post points at.

Edited by - Fruny on November 22, 2001 3:42:52 PM

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