How to catch opened event on a ComboBox with Dojo? - dojo

Question

I want to know whether a combo box has been opened and call a function that displays an progress bar while it loads the data from a store. I've check the API but no I didn't find any suitable event for what I'm doing.
EDIT
What I want to do is start a progress bar while the combobox is populated from the store. I've created a widget with the combobox and the progress bar (a custom class) and "decorate" openDropDown function with aspect.before. This is the code I've written:
postCreate: function() {
this.inherited(arguments);
aspect.before(
this.comboBox, 'openDropDown',
lang.hitch(this, function(){
this.progressBar.increase();
})
);
on(
this.comboBox,
'search',
lang.hitch(this.progressBar, 'decrease')
);
}
But it seems is not using the right progressBar object.

Answer 1

It sounds like you are looking for something like an "onOpen" event. as of Dojo 1.10 The Dijit/Combobox widget does not support an event like the one you are describing, however it does support a number of other events that might meet your requirements.
I recommend looking into the api for a list of possible events: http://dojotoolkit.org/api/
However the following code will create a custom "onOpen" event like what you are describing. I've provided a jsfiddle which demos this new event
http://jsfiddle.net/kagant15/z4nvzy44/
var comboBox = new ComboBox({
id: "stateSelect",
name: "state",
value: "California",
store: stateStore,
searchAttr: "name"
}, "stateSelect")
// grab the existing openDropDown method
var openDropDownFunction = comboBox.openDropDown;
newFunction = function(){
topic.publish("openDropDown") // add the custom "openDropDown" event trigger
return openDropDownFunction.apply(this);
}
// replace the old comBox method will our new function
comboBox.openDropDown = newFunction;
// Subscribe to the custom openDropDown event and do something when it fires
topic.subscribe("openDropDown", function(){
console.log("Open Drop Down even trigger");
});