Method Chaining in MooTools and PHP

One of the great parts of most every JavaScript and PHP framework these days is the ability to chain class methods. I've gotten quite a few question about how this is possible so I want to cover the basics of allowing chaining in your own custom classes.

Lets first start by implementing some new methods on the MooTools Element class:

/* implement functionality */
Element.implement({
	doTaskA: function() {
		/* do stuff */
	},
	doTaskB: function() {
		/* do stuff */
	}
});

What the above methods actually do really isn't very important per this post. Now that you have these methods in place, you try the following:

/* Example */
$('myElement').doTaskA().doTaskB();

Good? Nope. You'll end up with the following error:

$('myElement').doTaskA() is undefined

What? doTaskA() definitely exists!! Why is this error occuring? While doTaskA() does exist, the method doesn't return anything.

The strategy for method chaining is returning a reference to the current object. How? Lets update the doTaskA() and doTaskB() methods to allow for method chaining:

Element.implement({
	doTaskA: function() {
		/* do stuff */
		return this;
	},
	doTaskB: function() {
		/* do stuff */
		return this;
	}
});

Returning this keeps the reference which in turn keeps the ability to chain alive. You can do the same thing in PHP:

public function doTaskA() {
	return $this;
}

public function doTaskB() {
	return $this;
}

/* usage */
$myObject->doTaskA()->doTaskB();

Class method chaining is a great way to keep your code condensed. Don't get too carried away with chaining though -- be sure to balance chaining with readability.