Hi Subbu

Squeak 2.4 had a WorldMorph class as a subclass of PasteUpMorph.
But Squeak 2.4 had no WorldState class..

In Squeak 2.5 a WorldState class was introduced and the WorldMorph
class was removed.

Squeak 2.5 has

    PasteUpMorph
    isWorldMorph

        	^ worldState notNil

Pharo (a fork of 3.8 or 3.9?) then later introduced WorldMorph as a
subclass of PasteUpMorph.

More research is need ......

Regards
Hannes



On 5/10/17, K K Subbu <kksubbu.ml at gmail.com> wrote:
> Hi,
>
> Is there any specific reason why WorldMorph is not a subclass of
> PasteUpMorph? The latter uses a variable to hold significant world state
> and rest of Morphic use isWorldMorph to check the type before calling
> methods.
>
> I would have expected subclassing and double-dispatch to yield smaller
> and cleaner code.
>
> Regards .. Subbu
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