I agree that chapter is required reading! I thought the code Mark had
written would work since views are constructed before they are
initialized (where attribute expressions would be resolved), and I
think, script blocks get executed as soon as they are constucted so that
debug code isn't particularly helpful.
In fact, I've just proved that Mark's code does work. I added
onconstruct and oninit events:
<canvas debug="true">
<class name="Bug">
<attribute name="storeView" type="expression"/>
</class>
<view name="cuteView">
<method event="onconstruct">
Debug.write('onconstruct', this);
</method>
<method event="oninit">
Debug.write('oninit', this);
</method>
</view>
<Bug name="bugInstance" storeView="$once{parent.cuteView}">
<method event="onconstruct">
Debug.write('onconstruct', this);
</method>
<method event="oninit">
Debug.write('oninit', this);
Debug.write('this.storeView', this.storeView);
</method>
</Bug>
<script>
Debug.write('script: ',bugInstance.storeView);
bugInstance.storeView.setAttribute("x",2);
</script>
</canvas>
The debugger output is:
onconstruct #cuteView
onconstruct #bugInstance
script: null
WARNING: test2.lzx:25: call to undefined method 'setAttribute'
oninit #cuteView
oninit #bugInstance
this.storeView #cuteView
On Fri, Jun 16, 2006 at 12:56 PM, Jason Stafford wrote:
> If you add the following line to the beginning of your script, you'll
> see that the view in question is not yet initialized:
> Debug.write(bugInstance.isinited);
>
> Although they claim that this chapter is optional reading, I've found
> that in my own experience I've had to read it over and over again:
>
> http://www.openlaszlo.org/lps-latest/docs/guide/initialization-and-instantiation.html
>
> Generally I try to keep my code out of script blocks except for very
> special cases. It's much better to have the code as methods of views,
> then you are much less likely to run into these sorts of problems.
>
> hope that helps.
>
> Mark Engelberg wrote:
>> I keep running into weird behavior where attributes aren't
>> initialized
>> when I expect. Here's an example that doesn't work, although it
>> seems
>> like it should. Basically, I'm storing a reference to "cuteView" in
>> the "storeView" attribute of the Bug class. Yet, you'll see that
>> bugInstance.storeView is null at the time the script is invoked. Can
>> someone please elucidate why this doesn't work?
>>
>> <canvas debug="true">
>> <class name="Bug">
>> <attribute name="storeView" type="expression"/>
>> </class>
>> <view name="cuteView"/>
>> <Bug name="bugInstance" storeView="$once{parent.cuteView}"/>
>>
>> <script>
>> Debug.write(bugInstance.storeView);
>> bugInstance.storeView.setAttribute("x",2);
>> </script>
>> </canvas>
>> _______________________________________________
>> Laszlo-user mailing list
>> [email protected]
>> http://www.openlaszlo.org/mailman/listinfo/laszlo-user
>>
>
> --
> Jason Stafford
> Principal Developer
> Inspiration Software, Inc.
> The leader in visual thinking & learning
>
> Introducing INSPIRATION(r) 8, the essential tool to visualize, think,
> organize and learn. Students use Inspiration to plan, research and
> complete projects successfully. Learn more at www.inspiration.com.
> 503-297-3004 Extension 119
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>
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