Re: Constructor Behavior

I am learning Design Patterns so I pulled this piece of code off the
ng (decorator) . Now I am going through it with the debugger and
seeing what does what and I have found something I just don't
understand.

The constructor for CCoffeeDecorator has this in the list
CCoffeeComponent().


I see it hitting the CCoffeeComponent() constructor ... but I can't
figure out what this accomplishes. The only thing I can think of, is
that this sets the pointer type to CCoffeeComponent ... but I don't
understand the mechanics are behind it.

Randy

#include <iostream>
#include <string>

using namespace std;

/*
*******************************************************************************************************
   abstract base class ** normal - any class can be decorated.
   hide constructor prevent construction of a plain component
*
********************************************************************************************************/
class CCoffeeComponent {
public:
 virtual string Info() = 0;

protected:
 CCoffeeComponent () {};
 string m_Info;
};

/*
*******************************************************************************************************
   Furthermore we need a decorator class that "is-a" component and
stores a
   pointer to a passed component object:
   NOTE: the default NULL-pointer that is used as an end-marker of
the component chain
*
********************************************************************************************************/
class CCoffeeDecorator : public CCoffeeComponent {
public:
 CCoffeeDecorator( CCoffeeComponent* pComponent = 0) :
CCoffeeComponent(), m_pComponent( pComponent ) {};

public:
 virtual string Info() {
                          if( !m_pComponent )
                            return string("");

                           return m_pComponent->Info();
                         }; // delegate info call to actual
implementation

protected:
 CCoffeeComponent* m_pComponent;

};
[..]