Rails spinoffs - Mar 2006 - RE: extending an existing DOM object in a prototypeway

Gosh darn Outlook seems to have stripped some newlines from my
response... last few lines should read...

var myActiveSpanBase = new ActiveSpan({"red"});

Object.extend($(''someSpan''), myActiveSpanBase);

$(''someSpan'').setup();

Or, more concisely...

Object.extend($(''someSpan''), new
ActiveSpan({"blue"});

$(''someSpan'').setup();

-----Original Message-----
From: rails-spinoffs-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
[mailto:rails-spinoffs-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org]
On Behalf Of Ryan
Gahl
Sent: Thursday, March 09, 2006 3:38 PM
To: rails-spinoffs-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
Subject: RE: [Rails-spinoffs] extending an existing DOM object in a
prototypeway

This is a good (and common) practice. A good rule I try to stick to is,
if more than 1 element needs some specific behaviors/functionality, make
a separate class for that, and extend the element with it when needed.

There are a couple things to keep in mind. One is, you almost always
will need to have a setup() method in your behavior class which you can
call after extending the element, which will actually handle wiring up
event handlers/activating the "widget". Two, keep handles to all your
event handlers (unlike what you did in your example), which leads to..
Three, define a dispose() method to clean up resources when the widget
(or behavior) is no longer needed...

Finally, I don''t do the extending from within the controller class,
like
in your example. I reserve the contructor arguments for other things,
like behavior options, etc.. (or sometimes for passing a reference to
the parent object), then I use an instance of the controller to do the
extension from the application (or outer object) scope.

Like so...

var ActiveSpan = Class.create();
ActiveSpan.prototype = {
	initalize: function(options) {
		// setup the widget options...
		this.options = Object.extend({...default options...},
options || {});
	},
	setup: function() {
		//making this an instance method ensures you are wiring
up events to a DOM element (i.e. the element has already been extended
with this class -- "this" will now be the DOM element extended with
the
ActiveSpan methods, and not just an "ActiveSpan")
		this.registerCallbacks();
	}
	registerCallbackss: function() {
		//ALWAYS store DOM handlers in variables so you can
dispose of them (prevent memory leaks)
		this.clickHandlerPointer this.clickHandler.bindAsEventListener(this);
		Event.observe(this, ''click'', this.clickHandlerPointer);
	},
	clickHandler: function(e) {
		this.style.background = this.options.color || "red";
	},
	dispose: function() {
		//get rid of the DOM event handlers...
		Event.stopObserving(this, ''click'',
this.clickHandlerPointer);
		this.clickHandlerPointer = null;

		//...other disposal code...
	}	
};

...Then in your calling code (I''m assuming it''s another
object)...

var myActiveSpanBase = new ActiveSpan({"red"});
Object.extend($(''someSpan''), myActiveSpanBase);
$(''someSpan'').setup();

Or, more concisely...

Object.extend($(''someSpan''), new
ActiveSpan({"blue"});
$(''someSpan'').setup();


I think you can see how this allows you some flexibility. You can either
use the same base instance to extend like elements, or you can use
different instances for each element when you need some custom setup.


-----Original Message-----
From: rails-spinoffs-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
[mailto:rails-spinoffs-bounces-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org]
On Behalf Of
Jeremy Kitchen
Sent: Thursday, March 09, 2006 3:12 PM
To: rails-spinoffs-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
Subject: [Rails-spinoffs] extending an existing DOM object in a
prototype way

I want to take an existing DOM object and extend it with some
functionality.  I know there''s a way to do this with prototype.
Unfortunately, I''m not entirely sure how to do this.

Basically, I want to take an existing DOM object and turn it into a
''widget'' by adding some functionality.

say we have a span:
<span id="blah">some text here</span>

I want to be able to, in javascript, do something like this:

var whatever = new ActiveSpan("blah");

and have the ActiveSpan class extend it with some functionality (like
onclick events, attributes, etc)

here''s what I have in mind, but I''m not sure this is exactly
correct:

var ActiveSpan = Class.create();
ActiveSpan.prototype = {
	initalize: function(span) {
		Object.extend(span, this);
		this.registerCallbacks();
	},
	registerCallbackss: function() {
		Event.observe(this, ''click'',
clickHandler.bindAsEventListener(this);
	},
	clickHandler: function(e) {
		this.style.background = "red";
	}
}

does this look right?  Also, I''ll eventually want to go through the
child elements in the initalize method to set those children up as well.
 The overall goal of this is to create an enhanced table class where you
just call a function and it does all sorts of things like handling
mouseovers, mouseouts, zebra striping, etc.

If I''m completely wrong, and someone has an example they can point me
at, that would be great!  If this looks ok, though, I''ll continue on
with it :)

If this is not possible, or if I have to attach my code to the object
like: span.BLAH = new ActiveSpan .. let me know :)  I just want to do
this in an as prototype-like way as possible.

-Jeremy

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