[fpc-devel] Interfaces documentation suggestion
graemeg at opensoft.homeip.net
Mon Aug 10 10:12:49 CEST 2009
Below is part of the Interfaces documentation. I disagree with the
documentation mentioned below.
Interfaces - section 7.1
"There are no visibility specifiers. All members are public (indeed, it
would make little sense to make them private or protected)."
Maybe it is just Joanna Carter and myself that disagree with this
statement. But here goes... Joanna and I both agree that Interfaces when
implemented in classes should rather be made private or protected
instead of public.
The reason is simple. You are supposed to (or preferred to) access the
methods via a Interface from another object instance and not the object
instance itself - in which case, even if the methods are private or
protected you will still have access to them via the Interface. Also the
object who implements the Interface will be able to access the methods
either way. But from another object instance - it is always preferred to
access those methods via a Interface.
lCriteria := nil;
if Supports(Visited, ItiFiltered, lFilter) then
if lFilter.HasCriteria then
lCriteria := lFilter.GetCriteria;
It might be worth mentioning this, instead of simply saying that there
is no point in having the Interface methods implemented as private or
protected. Also it (Borland docs) does say that there are no visibility
specifiers, but where does it say they are Public by default? That is
- Graeme -
fpGUI Toolkit - a cross-platform GUI toolkit using Free Pascal
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