This guide is intended to explain the @properties annotation through some simple examples.

Creating a Class with CocktailJS

To create a class in CocktailJS from scratch, we need to define a class constructor variable that will be used as a subject into the mix. The very basic structure looks like this:

MyClass.js

var cocktail = require('cocktail'),
    MyClass = function(){};

cocktail.mix(MyClass, {
    // ....
});

module.exports = MyClass;

Here we have created and exported our class MyClass. Right now there is nothing done in the mix since the option object is just an empty object. Let’s start adding some behavior to our class. In the following example we have added a simple method to display a message in the console which we called sayHello:

MyClass.js

var cocktail = require('cocktail'),
    MyClass = function(){};

cocktail.mix(MyClass, {

    sayHello: function(){
        console.log('Hello cocktail!');
    }

});

module.exports = MyClass;

Defining Properties

CocktailJS has a handy annotation @properties which helps you to define properties and their getters and setter. We are going to add a property named greeting into our MyClass so we can change the message on sayHello method.

First, we have to define the greeting property:

'@properties' : {
    greeting: 'Hello'
}

And then change the sayHello method to use the getter.

sayHello: function(){
    var greeting = this.getGreeting();

    console.log(greeting + ' cocktail!');
}

MyClass class will look like the following:

MyClass.js

var cocktail = require('cocktail'),
    MyClass = function(){};

cocktail.mix(MyClass, {

    '@properties' : {
        greeting: 'Hello'
    },

    sayHello: function(){
        var greeting = this.getGreeting();

        console.log(greeting + ' cocktail!');
    }

});

module.exports = MyClass;

Now we can use MyClass to produce different messages:

index.js

var MyClass = require('./MyClass'),
    obj;

obj = new MyClass();

obj.sayHello(); // prints "Hello cocktail!" since the default value is Hello

obj.setGreeting('Ahoy');
obj.sayHello(); // prints "Ahoy cocktail!"

obj.setGreeting('Yo');
obj.sayHello(); // prints "Yo cocktail!"

The ‘@properties’ annotation creates the getter and setter for you. It also adds the property to the subject (or subject’s prototype in case of classes). An special case is made when the defined property is a boolean. Here, instead of having a getter an isXXX method is created.

MyClass.js

var cocktail = require('cocktail'),
    MyClass = function(){};

cocktail.mix(MyClass, {

    '@properties' : {
        greeting: 'Hello',
        silent: false
    },

    sayHello: function(){
        var greeting = this.getGreeting();
        
        if(!this.isSilent()){
            console.log(greeting + ' cocktail!');    
        }
        
    }

});

module.exports = MyClass;

In the example above, we have added a property silent which defines if the sayHello() method will print the message to the console or not. Since silent is declared as false it is assumed as a boolean property then an isSilent method is created instead of getSilent.