On Wed, Aug 19, 2009 at 4:19 PM, Ronald Spengler <ron.spengler at gmail.com>wrote:

> When I (for example,) in a workspace, Command-P the text 'morph3874 color:
> Color red' and see 'aMorph(2413)', what does the number mean? I'm guessing
> it's some kind of object pointer. An OOP perhaps, I've heard people speak of
> those? This has been bugging me for a year, and I can't seem to construct a
> Google string that finds me an answer to the question. Can I use that number
> to find the object in the object memory?
> Why I ask:
>
> I'm presently trying to understand...
>
> http://bugs.squeak.org/bug_view_page.php?bug_id=456
>
>
Look at the code in Morph>>printOn:

Morph>>printOn: aStream
    | aName |
    super printOn: aStream.
    (aName := self knownName) notNil
        ifTrue: [aStream nextPutAll: '<' , aName , '>'].
    aStream nextPutAll: '('.
    aStream
        print: self identityHash;
        nextPutAll: ')'

This gets called when you do alt-p on a morph in a workspace. The
second-to-last line is of interest; this is the number that you're seeing.
It's an "identityHash". I'm not going to explain hashing here; Wikipedia can
teach you more if you're curious.

If you look at the implementation of ProtoObject>>identityHash, it is
primitive 75. If you look at the implementation of Object>>asOop, it is also
primitive 75. So, coincidentally, yes, it is an OOP (object pointer).

The intention however was just to print out a number that is unique for each
different instance so that you can see whether two variables are pointing to
the same morph. This is useful for debugging. In my own images, I often
modify printOn: methods to print out hashes or oops for the same reason.

I'm not sure how you'd convert an oop to an object. I guess you could search
through all objects in the image looking for the right one.

Gulik.

-- 
http://gulik.pbwiki.com/
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