http://pharo.org/

On 05.02.2015 17:14, nacho wrote:
Yes! Point me to those documents and I will love to read them!!!
thanks in advance


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On Thu, Feb 5, 2015 at 1:02 PM, Trygve Reenskaug [via Smalltalk] <[hidden email] </user/SendEmail.jtp?type=node&node=4804006&i=0>> wrote:


    Because your drawOn: method doesn't draw anything and needs help
    from super.
    It seems to me that you need to read more documentation :-)

    On 05.02.2015 15:53, nacho wrote:
    That work perfectly. What a silly mistake!!!
    Of course it should have been position := aPoint.
    Now, is it possible write the drawOn: method without calling
    super drawOn: a Canvas?
    I don't completely get it why I should call super drawOn: aCanvas
    thanks
    nacho


    *Lic. Ignacio Sniechowski, MBA**
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    On Thu, Feb 5, 2015 at 11:28 AM, Trygve Reenskaug [via Smalltalk]
    <[hidden email]
    <http:///user/SendEmail.jtp?type=node&node=4803979&i=0>> wrote:

        I've tested your code in Squeak and found another bug (I
        should have been more careful when I read your code. Shame on
        me.)

        In class Ball you have the methods

                position: aPoint
                        super position: aPoint.
        This does not set a value to your position variable in class Ball, but 
actually sets the upper-left corner of the bounds.
        You should have said position := aPoint.
        --------------------------------        
        The following now works in mySqueak image:
        EllipseMorph subclass: #Ball
                instanceVariableNames: 'position'
                classVariableNames: ''
                poolDictionaries: '' "this part is needed in Squeak"
                category: 'ZZZtesting'

        drawOn: aCanvas
                self borderWidth:10; borderColor: Color green.
                super drawOn: aCanvas.

        position
                ^ position.

        position: aPoint
                position := aPoint.

        I then execute the following in a workspace
            | aBall |
            aBall := Ball new.
            aBall position: ( 10@10 ).
            aBall openInWorld.

        and it seems to work. But closer scrutiny shows that it
        ignores your instance variable (position). when I move the
        ball around.
        The reason is that EllipseMorph  is a superclass of your Ball
        and cannot possibly know about an instance variable
        (position) that is defined in the subclass (Ball).

        I ignored Ball>position since the EllipseMorph doesn't use it:

        EllipseMorph subclass: #Ball
            instanceVariableNames: ''
            classVariableNames: ''
            poolDictionaries: ''
            category: 'ZZZtesting'

            position
                ^ super position.

            position: aPoint
               super position: aPoint.
        This looks better.
        I you really want to replace the EllipseMorph>position you
        must go deeper into how the EllipseMorph handles its position
        and bounds . This will not be trivial. Much easier to invent
        a new instance variable and use it in the drawOn: method.

        Good luck with your apprenticeship









        On 05.02.2015 11:56, nacho wrote:
        @Trygve
        I've checked and it doesn't work. I can't even bring the halo on to 
delete
        the morph. The debugger keeps popping.
        Thanks anyway to all
        Nacho




        -----
        Nacho
        Smalltalker apprentice.
        Buenos Aires, Argentina.
        --
        View this message in 
context:http://forum.world.st/Question-on-Morphic-drawOn-method-tp4803695p4803895.html
        Sent from the Pharo Smalltalk Users mailing list archive at Nabble.com.




--
        /The essence of object orientation is that objects
        collaborateto achieve a goal. /
        Trygve Reenskaug [hidden email]
        <http:///user/SendEmail.jtp?type=node&node=4803964&i=0>
        Morgedalsvn. 5A http://folk.uio.no/trygver/
        N-0378 Oslo http://fullOO.info
        Norway                     Tel: (+47) 22 49 57 27



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    Nacho Smalltalker apprentice. Buenos Aires, Argentina.

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    Trygve Reenskaug [hidden email]
    <http:///user/SendEmail.jtp?type=node&node=4804005&i=0>
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    Norway                     Tel: (+47) 22 49 57 27



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Nacho Smalltalker apprentice. Buenos Aires, Argentina.

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/The essence of object orientation is that objects collaborateto achieve a goal. /
Trygve Reenskaug mailto: tryg...@ifi.uio.no <mailto:%20tryg...@ifi.uio.no>
Morgedalsvn. 5A http://folk.uio.no/trygver/
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