[fpc-devel] Interface delegation fix: backport to FPC 2.4.2 ...?

[Marco van de Voort]

In our previous episode, Michael Van Canneyt said:
> >> Observable and Observer go hand in hand. We're talking about both.
> >> Specifically, I want to add observable to TPersistent.
> >
> > People having object frameworks based on that class will really thank you
> > for slowing their systems.
> 
> Why would it slow down?
> 
> I'm not adding any calls to it. Just a call and a property which - when used in a
> descendent - may instantiate an auxiliary object. By default, nothing is
> called, and therefor there is no speed impact.

How do you detect in an observable that the state changed ? Usually this is
done by setting a flag at any write operation to the object.