CODEWITHSUNDEEP
javascripteventsdojo
Allen Lin
Allen Lin

Reputation: 1209

Dojo Evented - "load" event is not fired/caught

I have a class that inherits dojo/Evented. I call the myClass.emit("load",{}) in my code. and listen to it by myClassInstance.on("load",function(){console.log("fired!")});

However, it's not fired. But interestingly, if I change to myClass.emit("myClass-load",{}) and listen by myClassInstance.on("myClass-load",function(){console.log("fire")}); the event get fired!

What did I miss here? Is it because other objects also listen to "load" event so it's not caught by myClassInstance?

Generally, what happens if two events, fired by two objects have the same name? Is it better to name each event uniquely?

Thanks, Allen

Upvotes: 0

Views: 168

Answers (1)

Ken Franqueiro
Ken Franqueiro

Reputation: 10559

If your class is inheriting dijit/_WidgetBase, there are a couple of differences in its treatment of on and emit that I might suspect are causing your issue.

Firstly, _WidgetBase won't emit DOM events before the widget has startup called or after/while it is destroyed. In other words, it won't emit DOM events during its constructor, postscript, buildRendering, and postCreate.

Secondly, _WidgetBase contains some admittedly convoluted logic for backwards compatibility with legacy widgets which implement events via methods following the onXxx naming pattern. While _WidgetBase#emit will still fire a DOM event even if a matching onXxx method exists, _WidgetBase#on will not listen for the DOM event if it finds an onXxx method first.

Therefore, I'd suggest making sure of 2 things:

  • emit isn't being called on the widget prior to startup
  • The widget doesn't already have an onLoad method

I suppose one final thing I should point out is that you shouldn't make a class inherit both _WidgetBase and Evented, as this may cause unintended side effects in widget logic, especially if you're extending an existing Dijit widget. Extending _WidgetBase alone should suffice since it already defines its own emit and on (linked above).

Upvotes: 1

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