root/trunk/openlayers/lib/OpenLayers/BaseTypes/Class.js

/* Copyright (c) 2006-2010 by OpenLayers Contributors (see authors.txt for 
 * full list of contributors). Published under the Clear BSD license.  
 * See http://svn.openlayers.org/trunk/openlayers/license.txt for the
 * full text of the license. */

/**
 * Constructor: OpenLayers.Class
 * Base class used to construct all other classes. Includes support for 
 *     multiple inheritance. 
 *     
 * This constructor is new in OpenLayers 2.5.  At OpenLayers 3.0, the old 
 *     syntax for creating classes and dealing with inheritance 
 *     will be removed.
 * 
 * To create a new OpenLayers-style class, use the following syntax:
 * > var MyClass = OpenLayers.Class(prototype);
 *
 * To create a new OpenLayers-style class with multiple inheritance, use the
 *     following syntax:
 * > var MyClass = OpenLayers.Class(Class1, Class2, prototype);
 * Note that instanceof reflection will only reveil Class1 as superclass.
 * Class2 ff are mixins.
 *
 */
OpenLayers.Class = function() {
    var Class = function() {
        /**
         * This following condition can be removed at 3.0 - this is only for
         * backwards compatibility while the Class.inherit method is still
         * in use.  So at 3.0, the following three lines would be replaced with
         * simply:
         * this.initialize.apply(this, arguments);
         */
        if (arguments && arguments[0] != OpenLayers.Class.isPrototype) {
            this.initialize.apply(this, arguments);
        }
    };
    var extended = {};
    var parent, initialize, Type;
    for(var i=0, len=arguments.length; i<len; ++i) {
        Type = arguments[i];
        if(typeof Type == "function") {
            // make the class passed as the first argument the superclass
            if(i == 0 && len > 1) {
                initialize = Type.prototype.initialize;
                // replace the initialize method with an empty function,
                // because we do not want to create a real instance here
                Type.prototype.initialize = function() {};
                // the line below makes sure that the new class has a
                // superclass
                extended = new Type();
                // restore the original initialize method
                if(initialize === undefined) {
                    delete Type.prototype.initialize;
                } else {
                    Type.prototype.initialize = initialize;
                }
            }
            // get the prototype of the superclass
            parent = Type.prototype;
        } else {
            // in this case we're extending with the prototype
            parent = Type;
        }
        OpenLayers.Util.extend(extended, parent);
    }
    Class.prototype = extended;
    return Class;
};

/**
 * Property: isPrototype
 * *Deprecated*.  This is no longer needed and will be removed at 3.0.
 */
OpenLayers.Class.isPrototype = function () {};

/**
 * APIFunction: OpenLayers.create
 * *Deprecated*.  Old method to create an OpenLayers style class.  Use the
 *     <OpenLayers.Class> constructor instead.
 *
 * Returns:
 * An OpenLayers class
 */
OpenLayers.Class.create = function() {
    return function() {
        if (arguments && arguments[0] != OpenLayers.Class.isPrototype) {
            this.initialize.apply(this, arguments);
        }
    };
};


/**
 * APIFunction: inherit
 * *Deprecated*.  Old method to inherit from one or more OpenLayers style
 *     classes.  Use the <OpenLayers.Class> constructor instead.
 *
 * Parameters:
 * class - One or more classes can be provided as arguments
 *
 * Returns:
 * An object prototype
 */
OpenLayers.Class.inherit = function () {
    var superClass = arguments[0];
    var proto = new superClass(OpenLayers.Class.isPrototype);
    for (var i=1, len=arguments.length; i<len; i++) {
        if (typeof arguments[i] == "function") {
            var mixin = arguments[i];
            arguments[i] = new mixin(OpenLayers.Class.isPrototype);
        }
        OpenLayers.Util.extend(proto, arguments[i]);
    }
    return proto;
};