# Yahoo! UI Library

### base 3.0.0b1

Yahoo! UI Library > base > Base.js (source view)
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        /**
         * The base module provides the Base class, which objects requiring attribute and custom event support can extend.
         * The module also provides two ways to reuse code - An augmentable Plugin.Host interface which provides plugin support
         * (which is augmented to the Base class) and Base.build which provides a way to
         * build custom classes using extensions.
         *
         * @module base
         */

        /**
         * The base-base submodule provides the Base class and augmentable Plugin.Host implementation,
         * without the extension support provided by Base.build.
         *
         * @module base
         * @submodule base-base
         */
        var O = Y.Object,
            DOT = ".",
            DESTROY = "destroy",
            INIT = "init",
            INITIALIZED = "initialized",
            DESTROYED = "destroyed",
            INITIALIZER = "initializer",
            OBJECT_CONSTRUCTOR = Object.prototype.constructor,
            DEEP = "deep",
            SHALLOW = "shallow",
            VALUE = "value",
            DESTRUCTOR = "destructor";

        /**
         * <p>
         * A base class which objects requiring attributes and custom event support can
         * extend. Base also handles the chaining of initializer and destructor methods across
         * the hierarchy as part of object construction and destruction. Additionally, attributes configured
         * through the static <a href="#property_Base.ATTRS">ATTRS</a> property for each class
         * in the hierarchy will be initialized by Base.
         * </p>
         *
         * <p>
         * The static <a href="#property_Base.NAME">NAME</a> property of each class extending
         * from Base will be used as the identifier for the class, and is used by Base to prefix
         * all events fired by instances of that class.
         * </p>
         * @class Base
         * @constructor
         * @uses Attribute
         * @uses Plugin.Host
         *
         * @param {Object} config Object with configuration property name/value pairs
         */
        function Base() {
            Y.log('constructor called', 'life', 'base');

            Y.Attribute.call(this);
            Y.Plugin.Host.call(this);

            this._silentInit = this._silentInit || false;
            if (this._lazyAddAttrs !== false) { this._lazyAddAttrs = true; }

            this.init.apply(this, arguments);
        }

        /**
         * The list of properties which can be configured for
         * each attribute (e.g. setter, getter, writeOnce, readOnly etc.)
         *
         * @property Base._ATTR_CFG
         * @type Array
         * @static
         * @private
         */
        Base._ATTR_CFG = Y.Attribute._ATTR_CFG.concat("cloneDefaultValue");

        /**
         * <p>
         * The string to be used to identify instances of
         * this class, for example in prefixing events.
         * </p>
         * <p>
         * Classes extending Base, should define their own
         * static NAME property, which should be camelCase by
         * convention (e.g. MyClass.NAME = "myClass";).
         * </p>
         * @property Base.NAME
         * @type String
         * @static
         */
        Base.NAME = 'base';

        /**
         * The default set of attributes which will be available for instances of this class, and
         * their configuration. In addition to the configuration properties listed by
         * Attribute's <a href="Attribute.html#method_addAttr">addAttr</a> method, the attribute
         * can also be configured with a "cloneDefaultValue" property, which defines how the statically
         * defined value field should be protected ("shallow", "deep" and false are supported values).
         *
         * By default if the value is an object literal or an array it will be "shallow" cloned, to
         * protect the default value.
         *
         * @property Base.ATTRS
         * @type Object
         * @static
         */
        Base.ATTRS = {
            /**
             * Flag indicating whether or not this object
             * has been through the init lifecycle phase.
             *
             * @attribute initialized
             * @readonly
             * @default false
             * @type boolean
             */
            initialized: {
                readOnly:true,
                value:false
            },

            /**
             * Flag indicating whether or not this object
             * has been through the destroy lifecycle phase.
             *
             * @attribute destroyed
             * @readonly
             * @default false
             * @type boolean
             */
            destroyed: {
                readOnly:true,
                value:false
            }
        };

        Base.prototype = {

            /**
             * Init lifecycle method, invoked during construction.
             * Fires the init event prior to setting up attributes and
             * invoking initializers for the class hierarchy.
             *
             * @method init
             * @final
             * @chainable
             * @param {Object} config Object with configuration property name/value pairs
             * @return {Base} A reference to this object
             */
            init: function(config) {
                Y.log('init called', 'life', 'base');

                /**
                 * The string used to identify the class of this object.
                 *
                 * @deprecated Use this.constructor.NAME
                 * @property name
                 * @type String
                 */
                this._yuievt.config.prefix = this.name = this.constructor.NAME;

                /**
                 * <p>
                 * Lifecycle event for the init phase, fired prior to initialization.
                 * Invoking the preventDefault() method on the event object provided
                 * to subscribers will prevent initialization from occuring.
                 * </p>
                 * <p>
                 * Subscribers to the "after" momemt of this event, will be notified
                 * after initialization of the object is complete (and therefore
                 * cannot prevent initialization).
                 * </p>
                 *
                 * @event init
                 * @preventable _defInitFn
                 * @param {EventFacade} e Event object, with a cfg property which
                 * refers to the configuration object passed to the constructor.
                 */
                if (!this._silentInit) {
                    this.publish(INIT, {
                        queuable:false,
                        defaultFn:this._defInitFn
                    });
                }

                if (config) {
                    if (config.on) {
                        this.on(config.on);
                    }
                    if (config.after) {
                        this.after(config.after);
                    }
                }

                if (!this._silentInit) {
                    this.fire(INIT, {cfg: config});
                } else {
                    this._defInitFn({cfg: config});
                }

                return this;
            },

            /**
             * <p>
             * Destroy lifecycle method. Fires the destroy
             * event, prior to invoking destructors for the
             * class hierarchy.
             * </p>
             * <p>
             * Subscribers to the destroy
             * event can invoke preventDefault on the event object, to prevent destruction
             * from proceeding.
             * </p>
             * @method destroy
             * @return {Base} A reference to this object
             * @final
             * @chainable
             */
            destroy: function() {
                Y.log('destroy called', 'life', 'base');

                /**
                 * <p>
                 * Lifecycle event for the destroy phase,
                 * fired prior to destruction. Invoking the preventDefault
                 * method on the event object provided to subscribers will
                 * prevent destruction from proceeding.
                 * </p>
                 * <p>
                 * Subscribers to the "after" moment of this event, will be notified
                 * after destruction is complete (and as a result cannot prevent
                 * destruction).
                 * </p>
                 * @event destroy
                 * @preventable _defDestroyFn
                 * @param {EventFacade} e Event object
                 */
                this.publish(DESTROY, {
                    queuable:false,
                    defaultFn: this._defDestroyFn
                });
                this.fire(DESTROY);
                return this;
            },

            /**
             * Default init event handler
             *
             * @method _defInitFn
             * @param {EventFacade} e Event object, with a cfg property which
             * refers to the configuration object passed to the constructor.
             * @protected
             */
            _defInitFn : function(e) {
                this._initHierarchy(e.cfg);
                this._initPlugins(e.cfg);

                if (!this._silentInit) {
                    this._set(INITIALIZED, true);
                } else {
                    this._conf.add(INITIALIZED, VALUE, true);
                }
            },

            /**
             * Default destroy event handler
             *
             * @method _defDestroyFn
             * @param {EventFacade} e Event object
             * @protected
             */
            _defDestroyFn : function(e) {
                this._destroyHierarchy();
                this._destroyPlugins();
                this._set(DESTROYED, true);
            },

            /**
             * Returns the class hierarchy for this object, with Base being the last class in the array.
             *
             * @method _getClasses
             * @protected
             * @return {Function[]} An array of classes (constructor functions), making up the class hierarchy for this object.
             * This value is cached the first time the method, or _getAttrCfgs, is invoked. Subsequent invocations return the
             * cached value.
             */
            _getClasses : function() {
                if (!this._classes) {
                    this._initHierarchyData();
                }
                return this._classes;
            },

            /**
             * Returns an aggregated set of attribute configurations, by traversing the class hierarchy.
             *
             * @method _getAttrCfgs
             * @protected
             * @return {Object} The hash of attribute configurations, aggregated across classes in the hierarchy
             * This value is cached the first time the method, or _getClasses, is invoked. Subsequent invocations return
             * the cached value.
             */
            _getAttrCfgs : function() {
                if (!this._attrs) {
                    this._initHierarchyData();
                }
                return this._attrs;
            },

            /**
             * A helper method used when processing ATTRS across the class hierarchy during
             * initialization. Returns a disposable object with the attributes defined for
             * the provided class, extracted from the set of all attributes passed in .
             *
             * @method _filterAttrCfs
             * @private
             *
             * @param {Function} clazz The class for which the desired attributes are required.
             * @param {Object} allCfgs The set of all attribute configurations for this instance.
             * Attributes will be removed from this set, if they belong to the filtered class, so
             * that by the time all classes are processed, allCfgs will be empty.
             *
             * @return {Object} The set of attributes belonging to the class passed in, in the form
             * of an object with attribute name/configuration pairs.
             */
            _filterAttrCfgs : function(clazz, allCfgs) {
                var cfgs = null, attr, attrs = clazz.ATTRS;

                if (attrs) {
                    for (attr in attrs) {
                        if (attrs.hasOwnProperty(attr) && allCfgs[attr]) {
                            cfgs = cfgs || {};
                            cfgs[attr] = allCfgs[attr];
                            delete allCfgs[attr];
                        }
                    }
                }

                return cfgs;
            },

            /**
             * A helper method used by _getClasses and _getAttrCfgs, which determines both
             * the array of classes and aggregate set of attribute configurations
             * across the class hierarchy for the instance.
             *
             * @method _initHierarchyData
             * @private
             */
            _initHierarchyData : function() {
                var c = this.constructor,
                    classes = [],
                    attrs = [];

                while (c) {
                    // Add to classes
                    classes[classes.length] = c;

                    // Add to attributes
                    if (c.ATTRS) {
                        attrs[attrs.length] = c.ATTRS;
                    }
                    c = c.superclass ? c.superclass.constructor : null;
                }

                this._classes = classes;
                this._attrs = this._aggregateAttrs(attrs);
            },

            /**
             * A helper method, used by _initHierarchyData to aggregate
             * attribute configuration across the instances class hierarchy.
             *
             * The method will potect the attribute configuration value to protect the statically defined
             * default value in ATTRS if required (if the value is an object literal, array or the
             * attribute configuration has cloneDefaultValue set to shallow or deep).
             *
             * @method _aggregateAttrs
             * @private
             * @param {Array} allAttrs An array of ATTRS definitions across classes in the hierarchy
             * (subclass first, Base last)
             * @return {Object} The aggregate set of ATTRS definitions for the instance
             */
            _aggregateAttrs : function(allAttrs) {
                var attr,
                    attrs,
                    cfg,
                    val,
                    path,
                    i,
                    clone,
                    cfgProps = Base._ATTR_CFG,
                    aggAttrs = {};

                if (allAttrs) {
                    for (i = allAttrs.length-1; i >= 0; --i) {
                        attrs = allAttrs[i];

                        for (attr in attrs) {
                            if (attrs.hasOwnProperty(attr)) {

                                // Protect config passed in
                                cfg = Y.mix({}, attrs[attr], true, cfgProps);

                                val = cfg.value;
                                clone = cfg.cloneDefaultValue;

                                if (val) {
                                    if ( (clone === undefined && (OBJECT_CONSTRUCTOR === val.constructor || L.isArray(val))) || clone === DEEP || clone === true) {
                                        Y.log('Cloning default value for attribute:' + attr, 'info', 'base');
                                        cfg.value = Y.clone(val);
                                    } else if (clone === SHALLOW) {
                                        Y.log('Merging default value for attribute:' + attr, 'info', 'base');
                                        cfg.value = Y.merge(val);
                                    }
                                    // else if (clone === false), don't clone the static default value.
                                    // It's intended to be used by reference.
                                }

                                path = null;
                                if (attr.indexOf(DOT) !== -1) {
                                    path = attr.split(DOT);
                                    attr = path.shift();
                                }

                                if (path && aggAttrs[attr] && aggAttrs[attr].value) {
                                    O.setValue(aggAttrs[attr].value, path, val);
                                } else if (!path){
                                    if (!aggAttrs[attr]) {
                                        aggAttrs[attr] = cfg;
                                    } else {
                                        Y.mix(aggAttrs[attr], cfg, true, cfgProps);
                                    }
                                }
                            }
                        }
                    }
                }

                return aggAttrs;
            },

            /**
             * Initializes the class hierarchy for the instance, which includes
             * initializing attributes for each class defined in the class's
             * static <a href="#property_Base.ATTRS">ATTRS</a> property and
             * invoking the initializer method on the prototype of each class in the hierarchy.
             *
             * @method _initHierarchy
             * @param {Object} userVals Object with configuration property name/value pairs
             * @private
             */
            _initHierarchy : function(userVals) {
                var lazy = this._lazyAddAttrs,
                    constr,
                    constrProto,
                    ci,
                    ei,
                    el,
                    classes = this._getClasses(),
                    attrCfgs = this._getAttrCfgs();

                for (ci = classes.length-1; ci >= 0; ci--) {

                    constr = classes[ci];
                    constrProto = constr.prototype;

                    if (constr._yuibuild && constr._yuibuild.exts && !constr._yuibuild.dynamic) {
                        for (ei = 0, el = constr._yuibuild.exts.length; ei < el; ei++) {
                            constr._yuibuild.exts[ei].apply(this, arguments);
                        }
                    }

                    this.addAttrs(this._filterAttrCfgs(constr, attrCfgs), userVals, lazy);

                    if (constrProto.hasOwnProperty(INITIALIZER)) {
                        constrProto.initializer.apply(this, arguments);
                    }
                }
            },

            /**
             * Destroys the class hierarchy for this instance by invoking
             * the descructor method on the prototype of each class in the hierarchy.
             *
             * @method _destroyHierarchy
             * @private
             */
            _destroyHierarchy : function() {
                var constr,
                    constrProto,
                    ci, cl,
                    classes = this._getClasses();

                for (ci = 0, cl = classes.length; ci < cl; ci++) {
                    constr = classes[ci];
                    constrProto = constr.prototype;
                    if (constrProto.hasOwnProperty(DESTRUCTOR)) {
                        constrProto.destructor.apply(this, arguments);
                    }
                }
            },

            /**
             * Default toString implementation. Provides the constructor NAME
             * and the instance ID.
             *
             * @method toString
             * @return {String} String representation for this object
             */
            toString: function() {
                return this.constructor.NAME + "[" + Y.stamp(this) + "]";
            }
        };

        // Straightup augment, no wrapper functions
        Y.mix(Base, Y.Attribute, false, null, 1);
        Y.mix(Base, PluginHost, false, null, 1);

        /**
         * Alias for <a href="Plugin.Host.html#method_Plugin.Host.plug">Plugin.Host.plug</a>. See aliased
         * method for argument and return value details.
         *
         * @method Base.plug
         * @static
         */
        Base.plug = PluginHost.plug;

        /**
         * Alias for <a href="Plugin.Host.html#method_Plugin.Host.unplug">Plugin.Host.unplug</a>. See the
         * aliased method for argument and return value details.
         *
         * @method Base.unplug
         * @static
         */
        Base.unplug = PluginHost.unplug;

        // Fix constructor
        Base.prototype.constructor = Base;

        Y.Base = Base;

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