[Laszlo-dev] Detecting classes

[P T Withington]

Could we see an example of your debug output?  That might give an  
insight.

Also, it seems the subclass test could be simplified to:

   childClass.prototype is lz.Pane

The 'is' operator understands mixins, whereas 'isPrototypeOf' does not.

On Jan 17, 2010, at 23:21, Rami Ojares / AMG <rami.ojares at archon.fi>  
wrote:

> Hi Tucker,
> When 4.7 was released the restructuring of tagname etc. forced me to  
> detect Pane tags as per your suggestion.
> Currently I can´t get it to work.
>
> Here's the situation:
>
> I have a createChildren method overridden in SplitPane class
> And from there I am calling the method you said would detect Pane  
> classes
> (I only changed c.class to c['class'] because compiler told me to.  
> And I put the declaration
> of variable outside of if statement)
>
> Now the isPane seems to return false everytime.
> Since I don't really understand what is going on in here I ask for  
> your guidance and assistance.
> <method name="createChildren" args="children"><![CDATA[
>      var splitpaneChildren = [];
>   var paneCount = 0;
>      for(var i=0; i<children.length; i++) {
>              var pane = children[i];
>       var divider;
>              if (isPane(pane)) {
>                      divider = {
>               'class': lz.Divider,
>               attrs: {
>                   width: this.dividerWidth,
>                   index: paneCount
>               }
>           };
>                      // add index attribute also to Pane
>           pane.attrs.index = paneCount;
>                      splitpaneChildren.push(divider);
>           splitpaneChildren.push(pane);
>           paneCount++;
>       }
>       else splitpaneChildren.push(pane);
>          }
>   super.createChildren(splitpaneChildren);
>   ]]></method>
>
> <method name="isPane" args="c"><![CDATA[
>   Debug.debug("c = %w", c);
>      var childClass;
>   if (c.name) childClass = lz[c.name];
>   else childClass = c['class'];
>      Debug.debug("childClass = %w", childClass);
>      var ret = lz['Pane'].prototype.isPrototypeOf 
> (childClass.prototype);
>   Debug.debug("returning %w", ret);
>   return ret;
> ]]></method>
>
> - rami
>> If you are trying to detect instances of <Pane> (even anonymous  
>> ones, which would be subclasses), the recommended approach would be  
>> to use the `is` operator as above.  But I see where your problem  
>> lies, you are trying to sort the child "specifications" before they  
>> have been instantiated.  To be totally accurate, that means you  
>> would have to look for `name` _or_ `class`, and that you would need  
>> to know if the tag or class is a subclass of the tag's class you  
>> are sorting on.
>>
>> Something like:
>>
>> function isPane(c) {
>>  if (c.name) {
>>    var childClass = lz[c.name];
>>  } else {
>>    var childClass = c.class;
>>  }
>>  return lz['Pane'].prototype.isPrototypeOf(childClass.prototype);
>> }
>>
>> [That last line is pretty obscure, we should probably offer a built- 
>> in `extends` or `isSubclassOf` predicate.]
>