Missing concepts behind StringArray in Script Contribution

Hi guys.

Suppose I have a custom component, and made an API in order to get ids of boxes that are in my component.

I want the designer to be able to parse all the ids I will send him, so in my .ztl file, I've made

StringArray getBoxesId() {*     return this.sendBoxesIdToRuntime;
*}

The value returned from sendBoxesIdToRuntime is like so :

"["id1","id2",...]"

Note the "" encapsulating the [ ] because actually properties can't hold plain javascript array, so it is "stringifyied".

In the Dialog Window of Script Text, when calling

var value = COMPONENT.getBoxesId();

I receive a StringArray (this is why DS is telling why when I hover above value variable), but I'm not able to call split method on it for example, as exepected in the documentation.

If I change StringArray to String in the .ztl, then doing a

APPLICATION.alert(value);

is showing me the right string (and in this case, DS offers me to call split method on it) :

["id1","id2",...]

Any idea why I'm not able to call methods that are supposed to be exposed for StringArray type ?

Is there something more I need to do in my .ztl file ?

Thanks.

Br,

Vincent