Public functions from within a jQuery plugin

Question

I love the jQuery plugin architecture, however, I find it frustrating (probably due to a lack of understanding on my part) when I want to retain a reference to the plugin instance to access properties or methods later on in my code.

Edit: I want to clarify that what I am really trying to do is retain a reference to the methods and properties used within the plugin, so that I can use them later

Lets take the case of a AJAX loading icon. In a more traditional OOP environment, I could do:

var myIcon = new AJAXIcon();
myIcon.start();
//some stuff
myIcon.stop();

The methods and properties of my object are stored on a variable for later use. Now if I want to have the same functionality in a jQuery plugin, I would call it from my main code somewhat like this:

$("#myId").ajaxIcon()

By convention, my plugin needs to return the original jQuery object passed to my plugin allowing for chainability, but if I do that, I loose the ability to access methods and properties of the plugin instance.

Now, I know that you can declare a public function in my plugin, somewhat along the lines of

$.fn.ajaxIcon = function(options) {
    return this.each(function () {
        //do some stuff
    }
}

$.fn.ajaxIcon.stop = function() {
    //stop stuff
}

However, without breaking the convention of returning the original jQuery object, I can't retain a reference to the specific instance of the plugin that I want to refer to.

I would like to be able to do something like this:

var myIcon = $("myId").ajaxIcon(); //myIcon = a reference to the ajaxIcon 
myIcon.start();
//some stuff
myIcon.stop();

Any thoughts?

Answer 1

If you do something like the following:

(function($){

$.fn.myPlugin = function(options) {
    // support multiple elements
    if (this.length > 1){
        this.each(function() { $(this).myPlugin(options) });
        return this;
    }

    // private variables
    var pOne = '';
    var pTwo = '';
    // ...

    // private methods
    var foo = function() {
        // do something ...
    }
    // ...

    // public methods        
    this.initialize = function() {
        // do something ...
        return this;
    };

    this.bar = function() {
        // do something ...
    };
    return this.initialize();
}
})(jQuery);

Then you can access any of your public methods:

var myPlugin = $('#id').myPlugin();

myPlugin.bar();

This is taken from this very helpful article (May 2009) from trulyevil.com which is itself an extension on this article (Oct 2007) from learningjquery.com.

Answer 2

Ok, i figured out how to do this:

Plugin Code:

$.ajaxIcon.init = function(element, options) {
    //your initialization code

    this.start = function() {
         //start code
    }

    this.stop = function() {
         //stop code
    }
}

$.fn.ajaxIcon = function(options) {
    this.each(function () {
        //This is where the magic happens
        jQuery(this).data('ajaxIcon', new jQuery.ajaxIcon.init(this, opts));
    });

return this;
}

Then to use it somewhere else in your code:

var myIcon = $("#myId").ajaxIcon.data('ajaxIcon') 
// myIcon: a reference to the 'init' object specific to this plugin instance
myIcon.start();
myIcon.stop();

voila, answered my own question :)

Answer 3

Sample plugin with all functions:

    <script type="text/javascript">
(function( $ ) {

    $.fn.PluginX = function( options ) {
        // Default variables
        // var defaults = {textColor: "#000", backgroundColor: "#fff"}
        // var opts = $.extend( {}, defaults, options );

        // Or
        var settings = $.extend( {}, $.fn.PluginX.defaults, options );

        // Private function
        var privFunc = function(txt) {
            return "Private function " + txt;
        };

        // Public function
        this.pubFunc = function(txt) {
            console.log("\r\nPublic function " + txt);
            return this;
        };

        // Public function2
        this.pubFunc2 = function(txt) {
            console.log("\r\nPublic function " + txt);

            // Private from public
            privFunc("\r\nPrivate function from public -- " + txt);
            return this;
        };

        // Our plugin implementation code goes here.
        return this.each(function() {
            // alert(opts.validate);
            $(this).on('click',function(){
                var elem = $( this );
                var markup = elem.text();                                
                console.log("\r\nElement text " + markup);

                // Function private
                console.log(privFunc(markup));

                // External func
                console.log($.fn.PluginX.format(markup));

                // External function
                console.log(external(markup));
            });

            return this;
        });
    };

    // Variable
    $.fn.PluginX.defaults = {
        validate: "username"
    };

    // External Function
    $.fn.PluginX.format = function(txt) {
        return "<strong>" + txt + "</strong>";
    };

    // External Function
    function external(txt){
        return "External " + txt;
    }

})(jQuery);

$(document).ready(function() {
    var pl = $('.txt').PluginX({validate: "words"}).pubFunc("Hello Public").pubFunc2("Hello Public2");        
});
</script>
<p class="txt">Hello Max</p>
<p class="txt">Hello Pax</p>