2014-03-20 8:43 GMT+01:00 Pharo4Stef <pharo4Stef@free.fr>:

On 20 Mar 2014, at 08:32, Yuriy Tymchuk <yuriy.tymchuk@me.com> wrote:

> Thank you all for your replies.
>
> I would say, that �Class Variable� name is a bit misleading, but now I know what is going on behind it. :)

Yes I would like to rename them to sharedVariable

It's exactly a shared variable, but that does not describe the scope.

It's a shared variable accessible in all methods of a class, its metaclass and their subclasses...
 

>
> Cheers!
> Uko
>
> On 19 Mar 2014, at 23:53, Ben Coman <btc@openinworld.com> wrote:
>
>> Yuriy Tymchuk wrote:
>>> Can anybody tell me what is the difference between the class variable on the "instance side� definition and instance variable on the �class side� definition?
>>>
>>> Thanks in advance.
>>> Uko
>>>
>>>
>> instance-variable: A variable that holds the private state of an object. In Smalltalk these can only be accessed by instance-methods.
>>
>> class-variable: An attribute of a class that is shared by that class, its subclasses, and  all  instances  of  those  classes.  Can  be  accessed  by  both  instance-methods and class-methods.
>>
>> class-instance-variable:  An attribute  of a class that  is not shared outside that specific class. Only the definition is inherited by subclasses, not the value .   Each subclass has its own private value. Accessible only by class-methods.
>>
>>
>> You will understand it best by experimenting.  Here is one I made for myself...
>>
>> ivCounter - instance variable counter
>> CVCounter - class variable counter
>> CIVCounter - class instance variable counter
>>
>> "----------"
>> Object subclass: #TestCounter
>>  instanceVariableNames: 'ivCounter iName'
>>  classVariableNames: 'CVCounter'
>>  poolDictionaries: ''
>>  category: 'MyExamples'
>>
>> TestCounter class  "accessed by clicking the <Class> button"
>>  instanceVariableNames: 'CIVCounter'
>>
>> TestCounter subclass: #TestSubCounter
>>  instanceVariableNames: ''
>>  classVariableNames: ''
>>  poolDictionaries: ''
>>  category: 'MyExamples'
>> "----------"
>> TestCounter    name: myInstanceName
>>  iName := myInstanceName.
>> TestCounter    >> next
>>  ivCounter ifNil: [ ivCounter := 0 ].
>>  CVCounter ifNil: [ CVCounter := 0 ].
>>  ivCounter := ivCounter + 1.
>>  CVCounter := CVCounter + 1.
>> TestCounter    >> printOn: aStream
>>  super printOn: aStream.
>>  aStream nextPutAll: ' ['.    aStream
>>      print: iName.
>>  aStream nextPutAll: '] ( '.    aStream
>>      nextPutAll: ' ivCounter=';
>>      print: ivCounter.
>>  aStream
>>      nextPutAll: ', CIVCounter=n/a'.
>>  aStream
>>      nextPutAll: ', CVCounter=';
>>      print: CVCounter.
>>  aStream nextPutAll: ' )'.   "----------"  TestCounter class >> next2
>>  CIVCounter ifNil: [ CIVCounter := 0 ].
>>  CVCounter ifNil: [ CVCounter := 0 ].
>>
>>  CIVCounter := CIVCounter + 1.
>>  CVCounter := CVCounter + 1.
>> TestCounter class >> printOn: aStream
>>  super printOn: aStream.
>>  aStream nextPutAll: ' ( '.    aStream
>>      nextPutAll: 'ivCounter=n/a'.
>>  aStream
>>      nextPutAll: ', CIVCounter=';
>>      print: CIVCounter.
>>  aStream
>>      nextPutAll: ', CVCounter=';
>>      print: CVCounter.
>>  aStream nextPutAll: ' )'.   TestCounter class >> reset
>>  CVCounter := nil.
>>  CIVCounter := nil.
>>
>> "---------"
>> Then from Workspace evaluate these...
>>
>> tc1 := TestCounter new.
>> tc2 := TestCounter new.
>>
>> tsc1 := TestSubCounter new.
>> tsc2 := TestSubCounter new.
>>
>> TestCounter reset.
>> TestSubCounter reset.
>>
>> tc1 next. tc2 next.
>> tc1 next.
>> tc2 next.
>>
>> tsc1 next.
>> tsc2 next.
>> tsc1 next.
>> tsc2 next.
>>
>> TestCounter next2.
>> TestCounter next2.
>> TestCounter next2.
>>
>>
>> TestSubCounter next2.
>> TestSubCounter next2.
>> TestSubCounter next2.
>>
>> cheers -ben
>>
>>
>>
>>
>>
>
>