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woo@ornl.gov(John W. Wooten) writes:

>I have an app in which I have a lot of elements, which may have
>many different geometrical shapes, but are subclassed from a general  
>element object which is a subclass of View.  As I build them, they are  
>stored in a list.

>I want them to be drawn in a View (myView) in myWindow.  Each element   
>subclass has a drawSelf method and each instance has it, of course.

>When my controller does a [myView display], the background appears, but  
>does each element have to be individually sent a [myElement drawSelf]?
>It then seems that they each have to be a subView of the original View.

>Somehow it should be simpler than this, so I think I'm missing  
>something.



>--
>-----------------
>J. W. Wooten

Well, {myView display] will only send display to myView and myView's subviews
which have been set up via view's addSubview.  Thus you should create a 
allGraphicsPerform method  and have it send a display to each element in the list.
Actually you can pass the method you wish to have executed as a parameter and
thus generalise even further.

Check out Summer NeXTWORLD , 1992 in Charles L. Perkins Article on Composition
makeSquaresPerform:

The code looks like 

- makeSquaresPerform:(SEL) aMessage {
return [[self viewList] makeObjectsPerform:aMessage];
}

If you wish to set up something that uses parameter passing. then you 
could try this.

- makeSquaresPerform:(SEL) aMessage with: anObject {
return [[self viewList] makeObjectsPerform:aMessage with: anObject];
}

Basically its makes use of behaviour already in List. 

replace [self viewList] with your list's reference or method
to retrieve its reference.

Hope this helps.

This code assumes that all your objects will perform "aMessage" perhaps
it might be worthwhile to check using Object's respondsTo: first.

ede978e@monu6.cc.monash.edu.au (Robert D. Nicholson) writes:
>woo@ornl.gov(John W. Wooten) writes:
>>I want them [list of varying elements] to be drawn in a View (myView) in
>>myWindow.  Each element subclass has a drawSelf method and each instance
>>has it, of course.

[Robert Nicholson's suggestion deleted, because it is essentially the same
as my own]

Or you could do it the way draw does it; when the myView is called on to draw
itself, it sends the draw method to the entire list.  Check out GraphicView,
in the Draw example source code.  All the elements are subclasses of Graphic.



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