Class.Attributes

Provides simple attributes definition with setters, getters, validators and change event handlers

How to use

All you have to do is add Attributes defenition to your class

#JS
var Employee = new Class({

	Attributes: {
		name: {
			value: 'Unnamed',
			validator: function(val) {
				return val.trim().length > 2;
			}
		},
		salary: {
			getter: function(val) {
				return this.get('currency') + val;
			}
		},
		currency: {
			value: '$'
		}
	},

	initialize: function(attributes) {
		this.setAttributes(attributes);
	}

});

Now you're able to create instance with initial attributes (like options)

#JS
var bob = new Employee({
	name: 'Bob',
	salary: 10000
});

Add events to listen attributes changes

#JS
bob.addEvent('salaryChange', function(event) {
	alert('Old salary: {oldVal}, new salary: {newVal}'.substitute(event));
});

Set attributes

#JS
bob.set('salary', 12000); // alert text: 'Old salary: 10000, new salary: 12000';

Get attributes

#JS
bob.get('salary'); // '$12000' - since we defined getter

Validate attributes

#JS
bob.set('name', 'B'); // Will not set name since we have length validator

Non-existing attributes

If you try to access non-existing attribute with .get() - by it will return undefined, if try to set it .set(attr, value) - nothing will happen. But you're able to control accessing non-existing attributes by $getter and $setter that will be called for such attributes

#JS
var Employee = new Class({

	Attributes: {
	    $getter: function(name) {
	        return Cookie.read(name);
	    },

	    $setter: function(name, value) {
	        Cookie.write(name, value)
	    },

		name: {
			value: 'Unnamed',
			validator: function(val) {
				return val.trim().length > 2;
			}
		}
	}

});

...

instance.get('age'); // -> returns Cookie 'age' as we defined such behaviour at $getter
instance.set('age', 1); // -> write 'age' to Cookies

Attribute properties

Attribute can have following properties:

• value - default value of the attribute
• valueFn - function that will run instead of simple value. Could be used if your value depends on other instance values. The difference with setter it that valueFn is executed only at the very first getter call.
• setter - method that will process value and store it when you use instance.set(attr, value)
• getter - method that will process stored value and return it when you use instance.get(attr)
• readOnly - if true setter won't change the value

Also when value is changed (in case it successfully validated) the instance fires attrChange event, e.g.: nameChange, salaryChange, etc. Event handler gets one parameter - object with newVal and oldVal properties.