datachanged event no workie for me.

[donalconlon]

Im trying to add a listener to my dataModel when it's reloaded with new data. But it doesn't seem to fire.

var dataModel;
        this.dataModel = new YAHOO.ext.grid.XMLDataModel(schema);
		this.dataModel.onLoad.subscribe(this.onLoad.createDelegate(this));
        
		this.dataModel.addListener('datachanged',this.dataChanged);

I'm just trying to fire a simple alert

	dataChanged : function(){
		alert('rows:' + this.dataModel.getRowCount())
	},

I"m trying to call the method after I reload the data using :

search : function(e){
        getEl('load-ind').show();
        var params = {"list" : "New%20RFC's","keyField":"SVP%5Fx0020%5FApprover","query": e};

		this.dataModel.load(...,,this.clearIndicator);

And another thing. If I put an alert() in 'clearIndicator', it does not fire. Why is this?

 clearIndicator : function(file){
        getEl('load-ind').hide();
alert('dataLoaded');
    },

[jack.slocum]

You are looking for the 'load' event, not datachanged. I don't think datachanged is ever fired internally, it's there for subclasses to have a way to notify observers (like the grid) that the entire data has changed and needs to be rerendered (for example if you overwrite the "data" internal variable).

An XHR load fires a sequence of events - rowsdeleted, rowsinserted and then load.

[donalconlon]

Thanks Jack.

I did actuall try 'load', but I was using:

this.dataModel.addListener('load',this.onLoad);

but if I use:

this.dataModel.addListener('load',this.onLoad.createDelegate(this));

it works. No sure why the first doesn't.

[jack.slocum]

The best way is:

this.dataModel.on('load',this.onLoad, this, true);

This way you only bind the scope once (I also like the shorter "on").

[Animal]

Thanks Jack.

I did actuall try 'load', but I was using:

this.dataModel.addListener('load',this.onLoad);

but if I use:

this.dataModel.addListener('load',this.onLoad.createDelegate(this));

it works. No sure why the first doesn't.

I've been tring to explain this to my colleague who I have trying to create a Date/time input widget+JSP tag.

Think of the function parameter as being a C function pointer. All the addListener function receives is a function pointer. It has no concept of what the "this" should be at the time in the future that that function will be called. By default, in browsers it is the "window" object.

That's why the next parameter to addListener is "scope", and the next again is override. That means override the default scope with the passed scope.

createDelegate is another way to bind a scope to a function.