Re: Outline and Table back to front
Re: Outline and Table back to front
- Subject: Re: Outline and Table back to front
- From: Andreas Mayer <email@hidden>
- Date: Mon, 20 Jun 2005 20:47:18 +0200
Am 20.06.2005 um 20:05 Uhr schrieb Thomas Davie:
No subclass should ever add functionality, because this breaks the
"is a" relationsip...
I'm sorry, but this is utter - um... - nonsense.
Subclasses *refine* the descriptions of their superclasses. They
always do so by *adding* functionality.
A such refined class usually restricts the set of objects that
adheres to the class, because those objects need to be able to
understand *more* messages than objects of the superclass.
NSOutlineView being a subclass of NSTableView is a perfect example.
And, of course, an outline view *is* a table view. It has rows and
columns. But a table view is *not* an outline view, since it can't
collapse it's rows.
Andreas
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