[Laszlo-dev] referencing nodes by id, how to set global vars?

[P T Withington]

I only suggest the conditional wrapping for performance reasons...  
'with' does not come for free. And the compiler is already doing the  
necessary analysis.

On Feb 9, 2008, at 10:15, Donald Anderson <dda at ddanderson.com> wrote:

> Why not wrap every function's contents with 'with (global)' ?
>
> And can user code do this with top level vars?
>
>   var blah = globalvar;
>
> That would need to be fully qualified (either by smart compiler or  
> user).
>
> On Feb 9, 2008, at 7:32 AM, P T Withington wrote:
>
>> This is probably the right time to bite the bullet and stop using  
>> the global namespace.  It has already cause problems with name  
>> collisions.  Per my comment, "global" should probably only mean "in  
>> this canvas's scope".  So, yes create an object that holds these  
>> global names.  Heck, you could even call it `global`... :)
>>
>> Our compiler already analyzes each method to determine if there are  
>> free references in the method.  We could use this analysis to  
>> insert a `with (global)` block around any such code, so that no  
>> user code would have to change.
>>
>> On 2008-02-08, at 23:31 EST, Henry Minsky wrote:
>>
>>> In DHTML and AS2, we get away with doing this for setting node  
>>> id's to
>>> be global vars:
>>>
>>> function setID ( id ){
>>>  //support for current system
>>>  if ((typeof(id) == 'string') && id.length) {
>>>      if ($debug) {
>>>          if (global[id] && global[id] !== this) {
>>>              Debug.warn('Redefining #%s from %w to %w',
>>>                         id, global[id], this);
>>>          }
>>>      }
>>>      this.id = id;
>>>      // TODO: [2006-03-22 ptw] Should id's really go in the
>>> user/canvas module?
>>>      global[ id ] = this;
>>>  } else {
>>>      if ($debug) {
>>>          // id is permitted to be null or undefined, meaning
>>>          // "don't id me"
>>>          if (id) {
>>>              Debug.error('Invalid id %w for %w', id, this);
>>>          }
>>>      }
>>>   }
>>>  //namespace system
>>>  //app[ id ] = this;
>>>  //local reference
>>>
>>> }
>>>
>>> This works because we aliased "global" to _root in AS2, and to
>>> "window" in DHTML.
>>>
>>> I don't see any way to do this in AS3. There doesn't seem to be any
>>> magic object whose properties
>>> become global vars. I'm not even sure how to get the runtime to set
>>> global id variables by name procedurally during
>>> instantiation even if we declare them.  I hacked the tag compiler to
>>> emit a list of top level var declarations for all id's, but
>>> I don't see how to emit the code for the instantiator to bind to  
>>> them
>>> when the nodes are created, because what can you put on the
>>> left side of the assignment?
>>>
>>> One solution would be to make an API change, and require all  
>>> globally
>>> named nodes to be referenced via some object
>>> like "lz", which we already are kind of pushing for class names.   
>>> Tons
>>> of user code would  have to be updated.
>>>
>>> To add one more twist of the knife, for the debugger eval mechanism,
>>> if we want to use globals, we need to have a list of them
>>> someplace to compile in to the little debugger stub template app,
>>> because that code is compiled independent of the application code.
>>>
>>>
>>>
>>>
>>>
>>>
>>> -- 
>>> Henry Minsky
>>> Software Architect
>>> hminsky at laszlosystems.com
>>
>
>
> --
>
> Don Anderson
> Java/C/C++, Berkeley DB, systems consultant
>
> voice: 617-547-7881
> email: dda at ddanderson.com
> www: http://www.ddanderson.com
>
>
>
>