[fpc-devel] Assigning to inherited property calls setter of the child class
nc-gaertnma at netcologne.de
Fri May 1 17:39:43 CEST 2009
On Sat, 2 May 2009 02:17:48 +1100
Alexander Klenin <klenin at gmail.com> wrote:
> On Sat, May 2, 2009 at 01:56, Mattias Gaertner
> <nc-gaertnma at netcologne.de> wrote:
> >> 4) If it has setter named "SetP", do the equivalent of "inherited
> >> SetP".
> > Why?
> Because this surprises developers and leads to bugs.
> See the issue http://bugs.freepascal.org/view.php?id=13418
> (linked from the discussed one) for a recent example.
As Jonas already noted:
'That entirely depends on what you expect. "inherited property" now
means "use the property as declared in the parent class", which in a sense is logical.'
You can create a bug report for the documentation that only mentions
methods and maybe this is the reason for the confusion.
TAncestor = class
procedure SetP1(const AValue: integer); virtual;
property P: integer write SetP1;
TClassA = class(TAncestor)
procedure SetP1(const AValue: integer); override;
procedure SetP2(const AValue: char);
property P: char write SetP2;
inherited P:=3; // use property P of the ancestor,
// which calls SetP1, which is overridden in TClassA
// It does *not* call SetP1 of the ancestor
// To call the ancestor SetP1 use
> > "inherited P" should look up P in the ancestor class.
> > The setter of P belongs to the internal implementation of
> > the class. If you want to access the inherited setter, call it with
> > inherited SetP.
> Alternative solution would be to issue a warning if
> TInherited.SetP contains "inherited P := V" and SetP is virtual.
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