# ease.js

ease.js is a basic collection of CommonJS modules intended to "ease" the
transition into JavaScript from other Object-Oriented languages. It provides an
intuitive means of achieving classical inheritance and has planned support
traits/mixins.

Current support includes:

* Simple and intuitive class definitions
* Classical inheritance
* Abstract classes and methods
* Interfaces
* Visibility (public, protected and private members)
* Static, constant and final members

While the current focus of the project is Object-Oriented design, it is likely
that ease.js will expand to other paradigms in the future.

**This project is still under development. Please read the manual for more
information.**

## Why ease.js?
There are already plenty of other means of achieving each of this project's
goals, so what's the point of ease.js? The aim of the project is to provide a
lightweight library in a CommonJS format which also addresses ES5 issues and is
an all-inclusive solution to OO techniques. It satisfies primarily a personal
itch.


## How to Use
Please note that, as the project is under active development, the API may change
until the first release.

ease.js uses the [CommonJS](http://commonjs.org) module format. In the
examples below, [Node.js](http://nodejs.org) is used.

### Defining Classes
The constructor is provided as the `__construct()` method (influenced by
[PHP](http://php.net)).

````javascript
    var Class = require( 'easejs' ).Class;

    // anonymous class definition
    var Dog = Class(
    {
        'private _name': '',

        'public __construct': function( name )
        {
            this._name = name;
        },

        'public bark': function()
        {
            console.log( 'Woof!' );
        },

        'public getName': function()
        {
            return this._name;
        }
    });
````

The above creates an anonymous class and stores it in the variable ``Dog``. You
have the option of naming class in order to provide more useful error messages
and toString() output:

````javascript
    var Dog = Class( 'Dog',
    {
        // ...
    });
````

### Extending Classes
Classes may inherit from one-another. If the supertype was created using
`Class.extend()`, a convenience `extend()` method has been added to it. Classes
that were not created via `Class.extend()` can still be extended by passing it
as the first argument to `Class.extend()`.

Multiple inheritance is not supported. ease.js is very generous with the options
it provides to developers as alternatives, so pick whichever flavor your are
most comfortable with: interfaces, traits or mixins. Multiple inheritance will
not be added in the future due to its problems which have been addressed by
interfaces and traits.

**Note that interfaces, traits and mixins are not yet available. They are
planned features and should be available shortly.**

````javascript
    var SubFoo = Foo.extend(
    {
        'public anotherMethod': function()
        {
        },
    });

    // if Foo was not created via Class.extend(), this option may be used (has
    // the same effect as above, even if Foo was created using Class.extend())
    var SubFoo = Class.extend( Foo,
    {
        'public anotherMethod': function()
        {
        },
    });
````

### Abstract Classes
Abstract classes require that their subtypes implement certain methods. They
cannot be instantiated. Classes are considered to be abstract if they contain
one or more abstract methods and are declared using `AbstractClass` rather than
`Class`. If a class contains abstract methods but is not declared abstract, an
error will result. Similarily, if a class is declared to be abstract and
contains *no* abstract methods, an error will be thrown.

````javascript
    var AbstractClass = require( 'easejs' ).AbstractClass;

    var AbstractFoo = AbstractClass(
    {
        // a function may be provided if you wish the subtypes to implement a
        // certain number of arguments
        'abstract public fooBar': [ 'arg' ],

        // alternatively, you needn't supply implementation details
        'abstract public fooBar2': [],
    });
````

If the abstract method provides implementation details (as shown by
`fooBar()`, subtypes must implement at least that many arguments or an exception
will be thrown. This ensures consistency between supertypes and their subtypes.

Abstract classes can be extended from just as an other class. In order for its
subtype to be instantiated, it must provide concrete implementations of each
abstract method. If any methods are left as abstract, then the subtype too will
be considered abstract and must be declared as such.

````javascript
    // can be instantiated because concrete methods are supplied for both
    // abstract methods
    var ConcreteFoo = Class.extend( AbstractFoo,
    {
        'public fooBar': function( arg )
        {
        },

        'public fooBar2': function()
        {
        },
    });

    // cannot be instantiated because one abstract method remains
    var StillAbstractFoo = AbstractClass.extend( AbstractFoo,
    {
        'public fooBar': function( arg )
        {
        },
    });
````

### Interfaces
Interfaces can be declared in a very similar manner to classes. All members of
an interface must be declared as abstract.

````javascript
    var MyType = Interface(
    {
        'abstract public foo': []
    });
````

To implement an interface, use the `implement()` class method:

````javascript
    var ConcreteType = Class.implement( MyType ).extend(
    {
        'public foo': function() {}
    });
````

Note that, if a concrete implementation for each method is not provided, the
implementing type must be declared abstract.


## Use of Reserved Words
Though JavaScript doesn't currently implement classes, interfaces, etc, it does
reserve the keywords. In an effort to ensure that ease.js will not clash, the
following precautions are taken:

* `Class` is used with a capital 'C'
* `Interface` is used with a capital 'I'
* Reserved keywords are quoted when used (e.g. in property strings)