[Laszlo-user] create a class by name

[P T Withington]

Thanks Eliot!  You are correct.  (I was thinking in Javascript,  
thanks for spotting this.)

If you define a class:

   <class name="TestClass" ...

This will define a Javascript class in the `lz` package.  So yes, if  
you are trying to dynamically instantiate the LZX class `TestClass`  
in script, my examples should read:

   new lz.TestClass();

Or:

   var theclass = lz.TestClass;
   ...
   new theclass();

Or:

   var theclassname = "TestClass";
   ...
   new lz[theclassname]();

---

For backwards compatibility with LPS 3, we also define LZX classes  
globally (if they do not conflict with an existing global  
definition).  That will eventually be phased out, so the above is  
more correct.

On 2007-10-12, at 15:39 EDT, Elliot Winard wrote:

> I thought it was preferable to use class objects that are in 'lz'  
> object rather than global[classname]
>
> Are the lz.* potentially going to go away?
> -e
>
> P T Withington wrote:
>> eval is very limited in the swf runtime.  It can only evaluate var  
>> and member expressions.
>>
>> Are you just trying to create a particular class, or do you need  
>> the class to be variable, or do you need the name of the class to  
>> be a variable?  E.g., you can just say:
>>
>>   new TestClass();
>>
>> Or:
>>
>>   var theclass = TestClass;
>>   ...
>>   new theclass();
>>
>> Or:
>>
>>   var theclassname = "TextClass";
>>   ...
>>   new global[theclassname]();
>>
>> All of these work.  Your mechanism is what is used to evaluate a  
>> general expression, and is required because of the limited nature  
>> of eval in the swf runtime.  It is basically calling back to the  
>> server, having the server compile the expression, and then loading  
>> the compiled code to evaluate it.
>>
>> In the DHTML runtime, eval is fully-featured, but remember it is a  
>> security hole.  If you allow arbitrary user input to be evalled,  
>> you really have no control...
>>
>>
>> On 2007-10-12, at 14:12 EDT, Ruben Reusser wrote:
>>
>>> Hi:
>>>
>>> Is it possible to create a class by name in OpenLaszlo? I tried:
>>>
>>> eval("new TestClass()");
>>>
>>> but this does not work. The only solution I could find was the  
>>> following:
>>>
>>> loader.request( { lz_load : false,lzt : "eval",proxied: true,url:  
>>> "__debugger.lzx",lz_script : "#file interactive-eval-0\nnew  
>>> TestClass()"} );
>>>
>>> not my favorite approach.
>>>
>>> Ruben
>>>
>>