extending of adding method?

[Bjoern Schliessmann]

Gerardo Herzig wrote:

> Hi all. I have a question about design. The general question would
> be: Where is the line beteween extending a class and adding new
> methods to that class?

What do you mean by "extending"? The Java "extends", which is really
inheritance?
 
> And the particular case im involved is:
> 
> I have a class (say USERCLASS) who implements a user interface.
> One of his methods is called `login'. Later on i got the order of
> implementing a `single login', which off course means a single
> user cant login if a session is already started for that user.
> Extending comes to my mind at first (it works good, actually). But
> now im thinikng if there some problem in adding a method to the
> USERCLASS class named single_login(), who will take care of
> applying the rules of single sign on.
> 
> Which one you guys will pick up? USERCLASS().single_login() or
> SINGLELOGINUSERCLASS().login()

Depends. Inheritance is, IMHO, only good if it makes code reusal
and/or maintainability easier. I've once read that inheritance
often only is wise in "is a" relationships, e. g. "car is a
vehicle", which means class "car" should inherit from
class "vehicle".

Regards,


Björn

-- 
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routing problems on the neural net