Hi Nacho,�

The red box with two crossing yellow lines indicates that you made a mistake in the drawOn: method.

Whenever that happens, here is a tip that might help you. If you can't easily spot your error, you can debug it by evaluating:

aBall drawOn: Display getCanvas.

This will bring up the debugger and hopefully give you more information.

Best regards,

Richo

On Wed, Feb 4, 2015 at 3:00 PM, nacho <0800nacho@gmail.com> wrote:

Hi,
I have the following question:
I want to draw a bouncing ball.
First thing I do is create a class:

EllipseMorph subclass: #Ball
� � � � instanceVariableNames: 'position'
� � � � classVariableNames: ''
� � � � category: 'PBE-BouncingBall'

Then an initialization method that mostly do a super initialize.
Then the drawOn:

drawOn: aCanvas
� � � � aCanvas borderWidth:10; borderColor: Color green.

And finally a position method:

position: aPoint
� � � � super position: aPoint.

position
� � � � ^ position.

Finally in a Playground I do:

| aBall |

aBall := Ball new.
aBall position: ( 10@10 ).
aBall openInWorld.

But I get a red box with two crossing yellow lines.
What I'm missing?

Thanks in advance.
Nacho

-----
Nacho
Smalltalker apprentice.
Buenos Aires, Argentina.
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