# Yahoo! UI Library

### base 3.0.0b1

Yahoo! UI Library > base > PluginHost.js (source view)
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        /**
         * <p>
         * An augmentable class, which provides the augmented class with the ability to host plugins.
         * It adds <a href="#method_plug">plug</a> and <a href="#method_unplug">unplug</a> methods to the augmented class, which can
         * be used to add or remove plugins from instances of the class.
         * </p>
         *
         * <p>Plugins can also be added through the constructor configuration object passed to the host class' constructor using
         * the "plugins" property. Supported values for the "plugins" property are those defined by the <a href="#method_plug">plug</a> method.
         *
         * For example the following code would add the AnimPlugin and IOPlugin to Overlay (the plugin host):
         * <xmp>
         * var o = new Overlay({plugins: [ AnimPlugin, {fn:IOPlugin, cfg:{section:"header"}}]});
         * </xmp>
         * </p>
         * <p>
         * Plug.Host's protected <a href="#method_initPlugins">_initPlugins</a> and <a href="#method_destroyPlugins">_destroyPlugins</a>
         * methods should be invoked by the host class at the appropriate point in the host's lifecyle. This is done by default for
         * the Base class, so developers extending Base or Widget don't need to do anything to enable plugin support.
         * </p>
         *
         * @class Plugin.Host
         */

        var L = Y.Lang;

        function PluginHost(config) {
            this._plugins = {};
        }

        PluginHost.prototype = {

            /**
             * Adds a plugin to the host object. This will instantiate the
             * plugin and attach it to the configured namespace on the host object.
             *
             * @method plug
             * @chainable
             * @param p {Function | Object |Array} Accepts the plugin class, or an
             * object with a "fn" property specifying the plugin class and
             * a "cfg" property specifying the configuration for the Plugin.
             * <p>
             * Additionally an Array can also be passed in, with the above function or
             * object values, allowing the user to add multiple plugins in a single call.
             * </p>
             * @param config (Optional) If the first argument is the plugin class, the second argument
             * can be the configuration for the plugin.
             * @return {Base} A reference to the host object
             */

            plug: function(p, config) {
                if (p) {
                    if (L.isFunction(p)) {
                        this._plug(p, config);
                    } else if (L.isArray(p)) {
                        for (var i = 0, ln = p.length; i < ln; i++) {
                            this.plug(p[i]);
                        }
                    } else {
                        this._plug(p.fn, p.cfg);
                    }
                }
                return this;
            },

            /**
             * Removes a plugin from the host object. This will destroy the
             * plugin instance and delete the namepsace from the host object.
             *
             * @method unplug
             * @param {String | Function} plugin The namespace of the plugin, or the plugin class with the static NS namespace property defined. If not provided,
             * all registered plugins are unplugged.
             * @return {Base} A reference to the host object
             * @chainable
             */
            unplug: function(plugin) {
                if (plugin) {
                    this._unplug(plugin);
                } else {
                    var ns;
                    for (ns in this._plugins) {
                        if (this._plugins.hasOwnProperty(ns)) {
                            this._unplug(ns);
                        }
                    }
                }
                return this;
            },

            /**
             * Determines if a plugin has plugged into this host.
             *
             * @method hasPlugin
             * @param {String} ns The plugin's namespace
             * @return {boolean} returns true, if the plugin has been plugged into this host, false otherwise.
             */
            hasPlugin : function(ns) {
                return (this._plugins[ns] && this[ns]);
            },

            /**
             * Initializes static plugins registered on the host (using the
             * Base.plug static method) and any plugins passed to the
             * instance through the "plugins" configuration property.
             *
             * @method _initPlugins
             * @param {Config} config The configuration object with property name/value pairs.
             * @private
             */
            _initPlugins: function(config) {

                // Class Configuration
                var classes = this._getClasses(),
                    plug = [],
                    unplug = {},
                    constructor, i, classPlug, classUnplug, pluginClassName;

                //TODO: Room for optimization. Can we apply statically/unplug in same pass?
                for (i = classes.length - 1; i >= 0; i--) {
                    constructor = classes[i];

                    classUnplug = constructor._UNPLUG;
                    if (classUnplug) {
                        // subclasses over-write
                        Y.mix(unplug, classUnplug, true);
                    }

                    classPlug = constructor._PLUG;
                    if (classPlug) {
                        // subclasses over-write
                        Y.mix(plug, classPlug, true);
                    }
                }

                for (pluginClassName in plug) {
                    if (plug.hasOwnProperty(pluginClassName)) {
                        if (!unplug[pluginClassName]) {
                            this.plug(plug[pluginClassName]);
                        }
                    }
                }

                // User Configuration
                if (config && config.plugins) {
                    this.plug(config.plugins);
                }
            },

            /**
             * Unplugs and destroys all plugins on the host
             * @method _destroyPlugins
             * @private
             */
            _destroyPlugins: function() {
                this._unplug();
            },

            /**
             * Private method used to instantiate and attach plugins to the host
             *
             * @method _plug
             * @param {Function} PluginClass The plugin class to instantiate
             * @param {Object} config The configuration object for the plugin
             * @private
             */
            _plug: function(PluginClass, config) {
                if (PluginClass && PluginClass.NS) {
                    var ns = PluginClass.NS;

                    config = config || {};
                    config.host = this;

                    if (this.hasPlugin(ns)) {
                        // Update config
                        this[ns].setAttrs(config);
                    } else {
                        // Create new instance
                        this[ns] = new PluginClass(config);
                        this._plugins[ns] = PluginClass;
                    }
                }
            },

            /**
             * Unplugs and destroys a plugin already instantiated with the host.
             *
             * @method _unplug
             * @private
             * @param {String | Function} plugin The namespace for the plugin, or a plugin class with the static NS property defined.
             */
            _unplug : function(plugin) {
                var ns = plugin,
                    plugins = this._plugins;

                if (L.isFunction(plugin)) {
                    ns = plugin.NS;
                    if (ns && (!plugins[ns] || plugins[ns] !== plugin)) {
                        ns = null;
                    }
                }

                if (ns) {
                    if (this[ns]) {
                        this[ns].destroy();
                        delete this[ns];
                    }
                    if (plugins[ns]) {
                        delete plugins[ns];
                    }
                }
            }
        };

        /**
         * Registers plugins to be instantiated at the class level (plugins
         * which should be plugged into every instance of the class by default).
         *
         * @method Plugin.Host.plug
         * @static
         *
         * @param {Function} hostClass The host class on which to register the plugins
         * @param {Function | Array} plugin Either the plugin class, an array of plugin classes or an array of objects (with fn and cfg properties defined)
         * @param {Object} config (Optional) If plugin is the plugin class, the configuration for the plugin
         */
        PluginHost.plug = function(hostClass, plugin, config) {
            // Cannot plug into Base, since Plugins derive from Base [ will cause infinite recurrsion ]
            var p, i, l, name;

            if (hostClass !== Y.Base) {
                hostClass._PLUG = hostClass._PLUG || {};

                if (!L.isArray(plugin)) {
                    if (config) {
                        plugin = {fn:plugin, cfg:config};
                    }
                    plugin = [plugin];
                }

                for (i = 0, l = plugin.length; i < l;i++) {
                    p = plugin[i];
                    name = p.NAME || p.fn.NAME;
                    hostClass._PLUG[name] = p;
                }
            }
        };

        /**
         * Unregisters any class level plugins which have been registered by the host class, or any
         * other class in the hierarchy.
         *
         * @method Plugin.Host.unplug
         * @static
         *
         * @param {Function} hostClass The host class from which to unregister the plugins
         * @param {Function | Array} plugin The plugin class, or an array of plugin classes
         */
        PluginHost.unplug = function(hostClass, plugin) {
            var p, i, l, name;

            if (hostClass !== Y.Base) {
                hostClass._UNPLUG = hostClass._UNPLUG || {};

                if (!L.isArray(plugin)) {
                    plugin = [plugin];
                }

                for (i = 0, l = plugin.length; i < l; i++) {
                    p = plugin[i];
                    name = p.NAME;
                    if (!hostClass._PLUG[name]) {
                        hostClass._UNPLUG[name] = p;
                    } else {
                        delete hostClass._PLUG[name];
                    }
                }
            }
        };

        Y.namespace("Plugin").Host = PluginHost;

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