[Laszlo-dev] Is this the idiom people use to set the initial value of an attribute in a class declaration?

[Elliot Winard]

I always assumed that, unless $once{} was used, I was declaring a static 
attribute.  I thought that was noted in the docs.

Maybe not?
-e


On Mon, Jul 9, 2007 at  7:55 AM, P T Withington wrote:

> The bug we have is that we don't treat every instance initializer as 
> an expression, so you can't say `value="new Array"` to get around the 
> sharing, you have to say `value="${new Array}"`.  I think this is an 
> FAQ that Antun covers.
>
> And yes, you are right.  This would be solved by moving attribute 
> initializers into the class initializer.
>
> But if we fix this bug, we'll need to provide a way to share in the 
> cases where you _do_ want to share, perhaps by providing an LZX way to 
> declare a static attribute?
>
> On 2007-07-08, at 22:25 EDT, Henry Minsky wrote:
>
>> I've been hacking on an app this week, and realizing it's been 
>> awhile since
>> I tried
>> to actually program anything in Laszlo.
>>
>> There's this huge "gotcha" when setting the initial value of 
>> attributes to
>> an object in a class
>> declaration, like this
>>
>>
>> <class name="foo">
>>  <attribute name="pets" value="[]"/>
>>
>> Which screws you since that object will now be shared among all 
>> instances.
>>
>> The idiom I think I remember people using is
>>
>> <class name="foo">
>>  <attribute name="pets" value="$once{[]}"/>
>>
>> Or more readably
>>
>> <class name="foo">
>>  <attribute name="pets" value="$once{new Array()}"/>
>>
>> Is that what we recommend to do now? I guess we going to quietly  fix 
>> this
>> issue if and when we get
>> our node initialization rewritten as a compile-time-generated 
>> initializer
>> function?
>>
>>
>> -- 
>> Henry Minsky
>> Software Architect
>> hminsky at laszlosystems.com


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Elliot Winard
Sr. Software Engineer
Webtop Team
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