Re: how to maximize reusability?

David Wilkinson <>
Thu, 11 Oct 2007 07:32:28 -0400
Jack wrote:

I wonder what are the general methods to reuse a class component as much as
Like the case I showed you guys a few days ago

class CPerson : public CPathFinder

class CSupervisor : public CPerson

I'd like to declare and define once for one single method...
Some behaviours of classes are common, but don't know if I should put it in
the base class or derived class....
For example:
class CPathFinder

Render() is used in CPerson and CSupervisor. But Render() in CPathFinder
doesn't make sense cos it is not a tangiable object at all. How do I do
classifications and encapsulations here? also if I put render in CPerson, Do
all classes derived from CPerson needn't to declare and define the same
method again? That should be what is meant by "reusable"? No???


I'm not sure if I understand your question, but new virtual functions
can be introduced at any level of a class hierarchy, and then
overridden/implemented in classes derived from that level as necessary.
Not all the virtual functions have to be members of the ultimate base
class (here CPathFinder).

class CPathFinder

class CPerson : public CPathFinder
   virtual void Render() = 0;

class CSupervisor : public CPerson
   virtual void Render();

Of course CPathFinder has to provide some functionality (or interface)
used by CPerson, or the derivation does not make sense.

David Wilkinson
Visual C++ MVP

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