I have a class inheriting from Tpersistent:
type
TCondition=class( TPersistent, ICondition)
var
aCondition : TCondition;
but surprisingly, when I call
aCondition.FPOAttachObserver(someobj);
I discovered that nothing was executed.
I used debugger to step through this line and nothing was executed.
As a result, when this aCondition is destroyed, it won't notify the
observers.
I checked the source code "persist.inc", it is indeed implemented!
procedure TPersistent.FPOAttachObserver(AObserver: TObject);
Var
I : IFPObserver;
begin
If Not AObserver.GetInterface(SGUIDObserver,I) then
Raise EObserver.CreateFmt(SErrNotObserver,[AObserver.ClassName]);
If not Assigned(FObservers) then
FObservers:=TFPList.Create;
FObservers.Add(I);
end;
What is wrong? I am using FPC 3.1.1 trunk downloaded a few days ago.
From the documentation, there is this line:
TPersistent implements the IFPObserved
<http://www.freepascal.org/docs-html/rtl/classes/ifpobserved.html>
interface for the benefit of descendent classes, but does not call
IFPObserved.FPONotifyObservers
<http://www.freepascal.org/docs-html/rtl/classes/ifpobserved.fponotifyobservers.html>.
Descendents such as TStrings
<http://www.freepascal.org/docs-html/rtl/classes/tstrings.html> and
TCollection
<http://www.freepascal.org/docs-html/rtl/classes/tcollection.html> and
TCollectionItem
<http://www.freepascal.org/docs-html/rtl/classes/tcollectionitem.html>
do use it.
But the source code DOES CALL IFPObserved.FPONotifyObservers
<http://www.freepascal.org/docs-html/rtl/classes/ifpobserved.fponotifyobservers.html>!
destructor TPersistent.Destroy;
begin
If Assigned(FObservers) then
begin
FPONotifyObservers(Self,ooFree,Nil);
FreeAndNil(FObservers);
end;
inherited Destroy;
end;
Why did the documentation say that? Why was those code seemed not
linked at all? Some compiler options I messed up?
Dennis
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