variableWordSubclass:

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Joaquin Sitte a écrit :
> Please can someone explain the behaviour described below?
> I wish to create a subclass of FloatArray for a dynamic system
> simulation. When creating the class with #subclass: the method is
> automatically changed to #variableWordSubclass: as follows
 > [...]

In my opinion, this is the kind of questions you will more likely find
answers in squeak-dev.
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hi-

> So far I've seen the hierarchy of FloatArray the method "new:" isn't on the class side anywhere. This is the reason because you get an error.  

i'm a real rookie here, but what does it mean - "new:" isn't on the
class side anywhere?  where is "new:" then?

john cummings

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>>dv2 _ DynamicVariable new: 2
>  
> So far I've seen the hierarchy of FloatArray the method "new:" isn't on
> the class side anywhere. This is the reason because you get an error.  

#new: is implemented in Behavior which is the superclass of Class.

FloatArray new: 5

is correct for example
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 > where is "new:" then?

The method whose selector is #new: is implemented on the instance side
of Behavior and on the class side of some other classes (String, Set,
Array...).
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Hi John,



>> So far I've seen the hierarchy of FloatArray the method "new:"
>> isn't on the class side anywhere. This is the reason because you
>> get an error.  

cre> i'm a real rookie here, but what does it mean - "new:" isn't on the
cre> class side anywhere?  where is "new:" then?

if you can't find new: up the hierarchy the things to look for are
metaclsses and the class Behaviour. In the free books Stephane Ducasse
collected Hopkins Horan provides a chapter on this topic.

It's a bit brain twisting and when reading I decided I could get by
without really knowing about this detail :-))

Maybe someone else can shed more light on this, otherwise retry on
squeak-dev.

Cheers,

Herbert                            mailto:[hidden email]

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  Joaquin,

  I tried this and didn't get any error.  I managed to create an
instance of DynamicVariable with two slots.

> And, by the way, the method #variableWordSubclass cannot be found with Method Finder. Why?

  I'm not sure how you did this, but if you select from the "v" to "s"
above and press Ctrl-w (or Alt-Shift-w), you'll see the selectors that
contains the selected string as a part.

-- Yoshiki
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To understand a little bit more: When you execute (FloatArray new: 2), you send message #new: to class FloatArray with argument 2. message #new: is looked up in the receiver class methodDictionary, that is (FloatArray class) here. Note that FloatArray class is a an instance of Metaclass, which is a kind of Behavior. FloatArray class class. FloatArray class class superclass superclass. If #new: is not implemented in (FloatArray class), it must be in one of the superclass. FloatArray class allSuperclasses. You got an OrderedCollection(ArrayedCollection class SequenceableCollection class Collection class Object class ProtoObject class Class ClassDescription Behavior Object ProtoObject) What is causing you trouble is that the hierarchy browser is hiding this hierarchy... >From the Browser, FloatArray browseHierarchy you can only see: FloatArray allSuperclasses. And this one only show you a HierarchyBrowser on Metaclass: FloatArray class browseHierarchy. I remember from a browser showing the whole Metaclass hierarchy once (was it parcplace st-80 v2.3 ?). Maybe it would help newbies understand better this subtle part of Smalltalk. Hope it helps. Nicolas

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Sorry to repost, my webmail interface was using html instead of plain text...


To understand a little bit more:

When you execute (FloatArray new: 2), you send message #new: to class FloatArray with argument 2.

Message #new: is looked up in the receiver class methodDictionary, that is (FloatArray class) here.

Note that (FloatArray class) is a an instance of Metaclass:
FloatArray class class.
which is a kind of Behavior:
FloatArray class class superclass superclass.

If #new: is not implemented in (FloatArray class), it must be in one of its successive superclasses.
FloatArray class allSuperclasses.
You get
an OrderedCollection(ArrayedCollection class SequenceableCollection class Collection class Object class ProtoObject class Class ClassDescrip tion Behavior Object ProtoObject)

What is causing you trouble is that the hierarchy browser is hiding this hierarchy...
>From the Browser,
FloatArray browseHierarchy.
you can only see:
FloatArray allSuperclasses.
And this one only show you a HierarchyBrowser on Metaclass:
FloatArray class browseHierarchy.

I remember from a browser showing the whole Metaclass hierarchy once...
(was it parcplace st-80 v2.3 ?).
Maybe it would help newbies understand better this subtle part of Smalltalk.

Hope it helps.

Nicolas


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Many thanks to all who replied with advice.

Here is an update on the matter for those interested.

DynamicVariable is a subclass (variableWordSubclass) of FloatArray.
FloatArray new: 2  works!
Therefore because DynamicVariable is a subclass of FloatArray
DynamicVariable new: 2
should work, but id didn’t for me.

A partial solution to my problem was provided by Yoshiki Ohshima who
reported getting no error when executing

dv2 _ DynamicVariable new: 2

with DynamicVariable variable defined as a subclass of FloatArray.

That means I am doing something wrong. I tried to define another class
DynamicVariable2 in the same way, and do not get an error message when doing


dv2 _ DynamicVariable new: 2

Great!

But still my identically defined DynamicVariable  still does not understand
#new: (tried both Squeak 3.7 and 3.8 with identical results)

Obviously something is wrong somewhere in my system. Don’t know yet what.


 Thanks again


Joaquin

 

Dr. Joaquin Sitte,  Associate Professor.
School of Software Engineering and Data Communication Faculty of Information
Technology
Queensland University of Technology
GPO Box 2434, Brisbane, Q 4001 Australia
Phone +61 7 3864 2755
Fax +61 7 3864 1801
e-mail: [hidden email]
homepage http://www.fit.qut.edu.au/~sitte
 



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G'day Joaquin,

on Sun, 02 Jul 2006 14:39:07 +0200, wrote:
...
> But still my identically defined DynamicVariable  still does not  
> understand
> #new: (tried both Squeak 3.7 and 3.8 with identical results)
>
> Obviously something is wrong somewhere in my system. Don’t know yet what.
...

We can find out for you: just after you encounter the error, Squeak writes  
a file named SqueakDebug.log into its current directory. Feel free to post  
the contents of the file here and I'll see that I find you the bug.

/Klaus

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