SDK Custom Component - Change Attribute value

Hey,

I have an problem with my SDK Component; basically I have an image and on click I change an attribute("selection"). But when I use getSelection() in the Design Studio I don't get the expected value, but the old one.

My code is

 this.$().click(function() {           that.selection = "new value";            that.firePropertiesChanged(["selection"]);     that.fireEvent("onclick");
 }); 
this.selection = function(value){           if (value === undefined) {                return selection;           }else{                this.selection = value;                return this;           }
}; 

Do you have any idea, how to do it?

Thanks,

Philipp =)