Just to tell that I like this discussion. Now I have to digest it.
Because I still do not like classVariable, even if the life time is a 
good criteria.


On jeudi, novembre 28, 2002, at 03:05  am, Richard A. O'Keefe wrote:

> Roel Wuyts <roel.wuyts at iam.unibe.ch> wrote:
> 	I like the idea, but not these names, they are way to generic.
>
> Exactly so.
> 	Especially the 'knows' is really too much, and it is also a form of
> 	sharing (it just has a different scope). So maybe something like this?
> 	
> 	>> Morph
> 	>>     subclass: #MyMorph
> 	>>     has: ' myTarget lastTime '
> 	>>     instancesShare: ' CloseBoxImage '
> 	>>     poolsShare: ' Colors '
> 	>>     category: 'Morphic-Samples'!
> 	
> For me, 'has' is a relation between objects (THIS ordered collection
> _has_ THIS array as one of its parts) or a relation between classes
> (AN INSTANCE OF OrderedCollection _has_ AN INSTANCE OF Array).
> 	
> 'has' is not just "way too generic", it suggests the wrong thing.
>
> The most salient thing about #myTarget and #lastTime is that they
> are VARIABLE NAMES.  What on earth is wrong with using the word
> 'variable' here?
>
> The next most salient thing about these things is what their LIFETIME
> is.  Their lifetime is the lifetime of an instance.  So the most
> intention revealing name here is something that says
> 'variable with lifetime of instance', possibly in fewer words.
> I know, we could say 'instanceVariables:' and that would convey
> the meaning concisely and accurately.  It doesn't matter if it's
> a bit long because nobody ever types it.
>
> Now let's look at 'instancesShare'.  Let's find an example of instances
> sharing something.
>
>     x := 'boojum' copy.
>     y := Array with: x.
>     z := Array with: x.
>
> Now we have two instances (y, z) of Array sharing something.
> What they share is a String.
>
> Object sharing is FAR too important a concept in OO to abuse the
> word to refer to the scope of variable names.
>
> What's the most important thing about 'CloseBoxImage' here?
> The fact that it names a variable.
> What's the second most important thing about it?
> The fact that it has the same lifetime as the class.
> A good intention-revealing name would be something along the lines of
> 'variable with lifetime of class', possibly in fewer words.
> I know, we could use 'classVariables:' and that would convey
> the meaning concisely and accurately.  It doesn't matter if it's
> a bit long because nobody ever types it.
>
> Now let's look at 'poolsShare'.  Well, it's just plain WRONG.
> 'Colors' is not the name of something that some pools share',
> it is the name of a pool.  It would have to be 'poolsShared'.
> However, what's a pool?  Especially for beginners, you need
> a bit of help here.  A pool is a Dictionary, so we need a
> name something along the lines of
> 'dictionary of infinite extent variables whose scope may be
> shared with other not hierarchically related classes'.
> Since the things named aren't variables but dictionaries,
> we want something that says "xxxDictionaries:".  Anyone who
> knows/remembers Fortran would appreciate my preference,
> 'commonDictionaries:'.  "Pool" is the least obvious part of
> the name, so why retain the one bit that _isn't_ very helpful
> and jettison the part that _is_ helpful?
>
> 'instanceVariables:' and 'classVariables:' are well-nigh perfect
> intention-revealing names, once you grasp that the important 
> distinction
> is not whether they are "shared" or not (ALL Smalltalk variables can be
> "shared" in _some_ sense) but what their lifetime is.
>
> Remember that NOBODY types these names in by hand.
> Smalltalk makes the template for you, and you just fill in the
> different bits.
>
> Instead of messing about with the names (and thereby greatly 
> diminishing
> the utility of those wonderful free Smalltalk books), if anyone is
> seriously bothered about whether beginners understand these words or
> not, they could do something REALLY practical and potentially useful:
>
>     MAKE
> 	Class class>>templateForSubclassOf:category:
>     GENERATE A TEMPLATE THAT CONTAINS HELPFUL COMMENTS.
>
> So instead of seeing
>
>     Object subclass: #NameOfSubclass"
> 	instanceVariableNames: ''
> 	classVariableNames: ;;
> 	poolDictionaries: ''
> 	category: 'Collections-Text'
>
> a beginner would see
>
>     "Edit this template to create a new class."
>
>     Object subclass: #NameOfSubclass"
> 	instanceVariableNames: ''
> 	classVariableNames: ;;
> 	poolDictionaries: ''
> 	category: 'Collections-Text'
>
>     "Change Object to the name of the existing parent class.
>      Change NameOfSubclass to the name you want the new child class
>      to have.  Do not remove the # sign, it is important.
>      Instance variables are variables that live inside objects;
>      when an instance is made, the variable comes into existence;
>      when an instance disappears, the variable disappears.
>      To declare such variables, put their names, separated by spaces,
>      inside the string after instanceVariableNames:.
>      Class variables are variables associated with classes rather
>      than instances; when a class is created or loaded, they come
>      into existence, when the class is destroyed they go out of
>      existence, and they keep their values no matter how many
>      instances there are.
>      To declare class variables, put their names, separated by
>      spaces, inside the string after classVariableNames:.
>      Pool dictionaries are an advanced feature you don't need to use,
>      so leave that line untouched."
>
> I'm not picky about the wording.  It should certainly be localised.
> Basically, there is NO perfect set of words you can use here which
> will be instantly obvious to all people.  ESPECIALLY if you change
> the words so that they can't use any existing book!  Generating some
> kind of helpful comment, even if it's just
>     "Click on this link for a tutorial about creating classes."
> has got to be FAR more helpful.
>
>
Dr. Stéphane DUCASSE (ducasse at iam.unibe.ch) 
http://www.iam.unibe.ch/~ducasse/
  "if you knew today was your last day on earth, what would you do
  different? ... especially if, by doing something different, today
  might not be your last day on earth" Calvin&Hobbes