Thanks Mirko, that does indeed seem to be a bug with the subclassing mechanism.
The code fails when the base class is set to any of the widgets that set event
handlers in their constructor (eg <$scrollable>), but works for other widgets.
I wonder if you’d kindly be able to create a GitHub ticket?
Many thanks,
Jeremy
> On 23 Dec 2020, at 13:35, Mirko Richter <compago...@gmail.com> wrote:
>
>
> Hi,
>
> i tried to sublass the navigator as described in "WidgetSubclassingMechanism"
> like so:
>
>
> (function(){
>
> /*jslint node: true, browser: true */
> /*global $tw: false */
> "use strict";
>
> exports.baseClass = "navigator";
>
> // Specify a different name to make the subclass available as a new
> widget instead of overwriting the baseclass:
> exports.name = "limited-stack-navigator";
>
> exports.constructor = function(parseTreeNode,options) {
> this.initialise(parseTreeNode,options);
> };
>
> exports.prototype = {};
>
> exports.prototype.handleNavigateEvent = function(event) {
> /*event = $tw.hooks.invokeHook("th-navigating",event);
> if(event.navigateTo) {
> this.addToStory(event.navigateTo,event.navigateFromTitle);
> if(!event.navigateSuppressNavigation) {
>
> this.addToHistory(event.navigateTo,event.navigateFromClientRect);
> }
> }*/
> console.log("HANDLE");
> return false;
> };
>
> })();
>
> I get the following error: "this.eventListeners is undefined". It seems that
> the constructor of widget (the baseclass of navigator) is not called
> beforehand (which registers this.eventListeners ). So my basic questions here
> are:
> is this a design flaw? (e.g. the registration for the events inside of the
> navigator-constructor is a bad idea ;) )
> is it not intended to subclass navigator from some reason?
> am i doing something else (more trivial) wrong in my overwrite-trial above?
>
> Thanks for your help,
> Mirko
>
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