MooTools Class Creation Tips II

A while back I shared a few MooTools class creation tips that I live by. More experience in creating MooTools plugins has given me some new guidelines to share.

Code "Inline" First, Then Class-ize; Don't Force It

The number one tip I give to MooTools Class rookies is this: create the desired class functionality before turning it into a class. Once you have the code working using "inline" MooTools JavaScript, evaluate what you have. You may decide that your functionality is too specific to the task at hand that making a Class isn't the right choice.

If you do think you should turn the code into a class, take a look at all of your initial "var {key} = {value}" declarations -- those will likely be your arguments and options. Take any repeated code and turn them into class methods. Do the same for specific functionalities the Class should have. Here's a very basic example:

window.addEvent('domready',function() {
	/* settings */
	var showDuration = 3000;
	var container = $('slideshow-container');
	var images = container.getElements('img');
	var currentIndex = 0;
	var interval;
	var toc = [];
	var tocWidth = 20;
	var tocActive = 'toc-active';
	
	/* new: starts the show */
	var start = function() { interval = show.periodical(showDuration); };
	var stop = function() { $clear(interval); };
	/* worker */
	var show = function(to) {
		images[currentIndex].fade('out');
		toc[currentIndex].removeClass(tocActive);
		images[currentIndex = ($defined(to) ? to : (currentIndex < images.length - 1 ? currentIndex+1 : 0))].fade('in');
		toc[currentIndex].addClass(tocActive);
	};
	
	/* new: control: table of contents */
	images.each(function(img,i){
		toc.push(new Element('a',{
			text: i+1,
			href: '#',
			'class': 'toc' + (i == 0 ? ' ' + tocActive : ''),
			events: {
				click: function(e) {
					if(e) e.stop();
					stop();
					show(i);
				}
			},
			styles: {
				left: ((i + 1) * (tocWidth + 10))
			}
		}).inject(container));
		if(i > 0) { img.set('opacity',0); }
	});
	
	/* new: control: next and previous */
	var next = new Element('a',{
		href: '#',
		id: 'next',
		text: '>>',
		events: {
			click: function(e) {
				if(e) e.stop();
				stop(); show();
			}
		}
	}).inject(container);
	var previous = new Element('a',{
		href: '#',
		id: 'previous',
		text: '<<',
		events: {
			click: function(e) {
				if(e) e.stop();
				stop(); show(currentIndex != 0 ? currentIndex -1 : images.length-1);
			}
		}
	}).inject(container);
	
	/* new: control: start/stop on mouseover/mouseout */
	container.addEvents({
		mouseenter: function() { stop(); },
		mouseleave: function() { start(); }
	});
	
	/* start once the page is finished loading */
	window.addEvent('load',function(){
		start();
	});
});

And now the Class version:

var SimpleSlideshow = new Class({
	options: {
		showControls: true,
		showDuration: 3000,
		showTOC: true,
		tocWidth: 20,
		tocClass: 'toc',
		tocActiveClass: 'toc-active'
	},
	Implements: [Options,Events],
	initialize: function(container,elements,options) {
		//settings
		this.container = $(container);
		this.elements = $$(elements);
		this.currentIndex = 0;
		this.interval = '';
		if(this.options.showTOC) this.toc = [];
		
		//assign
		this.elements.each(function(el,i){
			if(this.options.showTOC) {
				this.toc.push(new Element('a',{
					text: i+1,
					href: '#',
					'class': this.options.tocClass + '' + (i == 0 ? ' ' + this.options.tocActiveClass : ''),
					events: {
						click: function(e) {
							if(e) e.stop();
							this.stop();
							this.show(i);
						}.bind(this)
					},
					styles: {
						left: ((i + 1) * (this.options.tocWidth + 10))
					}
				}).inject(this.container));
			}
			if(i > 0) el.set('opacity',0);
		},this);
		
		//next,previous links
		if(this.options.showControls) {
			this.createControls();
			
		}
		//events
		this.container.addEvents({
			mouseenter: function() { this.stop(); }.bind(this),
			mouseleave: function() { this.start(); }.bind(this)
		});

	},
	show: function(to) {
		this.elements[this.currentIndex].fade('out');
		if(this.options.showTOC) this.toc[this.currentIndex].removeClass(this.options.tocActiveClass);
		this.elements[this.currentIndex = ($defined(to) ? to : (this.currentIndex < this.elements.length - 1 ? this.currentIndex+1 : 0))].fade('in');
		if(this.options.showTOC) this.toc[this.currentIndex].addClass(this.options.tocActiveClass);
	},
	start: function() {
		this.interval = this.show.bind(this).periodical(this.options.showDuration);
	},
	stop: function() {
		$clear(this.interval);
	},
	//"private"
	createControls: function() {
		var next = new Element('a',{
			href: '#',
			id: 'next',
			text: '>>',
			events: {
				click: function(e) {
					if(e) e.stop();
					this.stop(); 
					this.show();
				}.bind(this)
			}
		}).inject(this.container);
		var previous = new Element('a',{
			href: '#',
			id: 'previous',
			text: '<<',
			events: {
				click: function(e) {
					if(e) e.stop();
					this.stop(); 
					this.show(this.currentIndex != 0 ? this.currentIndex -1 : this.elements.length-1);
				}.bind(this)
			}
		}).inject(this.container);
	}
});

See how easy the transition is when you have the inline code in front of you? Simple!

Add Events When Possible

Adding events to your classes gives a completely new level of control over the class functionality. Consider my Overlay class. I spent 95% of the time creating the plugin functionality and 5% implementing events but I consider events essential to the Overlay. Here's a quick example of implementing events:

//.....
Implements: [Options,Events],
open: function() {
	this.fireEvent('open');
	//do stuff
},
//.....

Now my Overlay class allows you fire events at 4 different times. More flexible and a perfect usage of events.

Evaluate Options vs. Arguments

Judge your list of options and your class' primary responsibilities to determine if all of the options should be kept as options and not as arguments, and visa versa. When I come to a 50/50 decision I choose to make the parameter an option. If the class cannot live without the given option/argument and there's no suitable default, keep it as an argument.

Chaining: return this;

One of the great advantages of using a JavaScript frameworks and classes is the ability to chain method class to make your code shorter. And implementing that type of functionality is so easy!

//.....
store: function(key,value) {
	this.data[key] = value;
	return this;
}
//.....

Don't let your methods end with nothing -- return this!

Put it in the Forge!

Share your awesome plugin by posting it in the MooTools Forge. Sharing your plugins in the Forge allows you to easily get feedback, improvements, and requests.

There you have it. Feel free to share any of your tips!