[Tutor] class question

[Alan Gauld]

"Dick Moores" <rdm at rcblue.com> wrote 

> Thanks. You've clarified it for me completely. 
> 
> Your second way seems to make more sense. 
> And instead of raising the error, why not just print it:

Because that would make the class much less reusable. 
It would be limited to applications using stdout. A GUI 
banking program would be unable to use the BankAccount 
class. But by raising an exception the user gets to decide 
what to do, either pop up a dialog, print a message or send 
an email to the banks client.

Its a primary design goal for reuse to de-couple business 
logic - like the bank account - from the user interface.

There is a bit more discussion around this in my 
Case Study topic where I convert it from command 
line to GUI and again in my InterProcess Comms topic 
where I turn the AddressBook into a client-server app.


HTH,

-- 
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld