The source code

    /**
     * @class Ext.Action
     * An Action is a piece of reusable functionality that can be abstracted out of any particular component so that it
     * can be usefully shared among multiple components.  Actions let you share handlers, configuration options and UI
     * updates across any components that support the Action interface (primarily {@link Ext.Toolbar}, {@link Ext.Button}
     * and {@link Ext.menu.Menu} components).
     * Aside from supporting the config object interface, any component that needs to use Actions must also support
     * the following method list, as these will be called as needed by the Action class: setText(string), setIconCls(string),
     * setDisabled(boolean), setVisible(boolean) and setHandler(function).
     * Example usage:

     *
    // Define the shared action.  Each component below will have the same
    // display text and icon, and will display the same message on click.
    var action = new Ext.Action({
        {@link #text}: 'Do something',
        {@link #handler}: function(){
            Ext.Msg.alert('Click', 'You did something.');
        },
        {@link #iconCls}: 'do-something',
        {@link #itemId}: 'myAction'
    });

    var panel = new Ext.Panel({
        title: 'Actions',
        width: 500,
        height: 300,
        tbar: [
            // Add the action directly to a toolbar as a menu button
            action,
            {
                text: 'Action Menu',
                // Add the action to a menu as a text item
                menu: [action]
            }
        ],
        items: [
            // Add the action to the panel body as a standard button
            new Ext.Button(action)
        ],
        renderTo: Ext.getBody()
    });

    // Change the text for all components using the action
    action.setText('Something else');

    // Reference an action through a container using the itemId
    var btn = panel.getComponent('myAction');
    var aRef = btn.baseAction;
    aRef.setText('New text');

     * @constructor
     * @param {Object} config The configuration options
     */
    Ext.Action = function(config){
        this.initialConfig = config;
        this.itemId = config.itemId = (config.itemId || config.id || Ext.id());
        this.items = [];
    }

    Ext.Action.prototype = {
        /**
         * @cfg {String} text The text to set for all components using this action (defaults to '').
         */
        /**
         * @cfg {String} iconCls
         * The CSS class selector that specifies a background image to be used as the header icon for
         * all components using this action (defaults to '').
         * An example of specifying a custom icon class would be something like:
         *
    // specify the property in the config for the class:
         ...
         iconCls: 'do-something'

    // css class that specifies background image to be used as the icon image:
    .do-something { background-image: url(../images/my-icon.gif) 0 6px no-repeat !important; }

         */
        /**
         * @cfg {Boolean} disabled True to disable all components using this action, false to enable them (defaults to false).
         */
        /**
         * @cfg {Boolean} hidden True to hide all components using this action, false to show them (defaults to false).
         */
        /**
         * @cfg {Function} handler The function that will be invoked by each component tied to this action
         * when the component's primary event is triggered (defaults to undefined).
         */
        /**
         * @cfg {String} itemId
         * See {@link Ext.Component}.{@link Ext.Component#itemId itemId}.
         */
        /**
         * @cfg {Object} scope The scope in which the {@link #handler} function will execute.
         */

        // private
        isAction : true,

        /**
         * Sets the text to be displayed by all components using this action.
         * @param {String} text The text to display
         */
        setText : function(text){
            this.initialConfig.text = text;
            this.callEach('setText', [text]);
        },

        /**
         * Gets the text currently displayed by all components using this action.
         */
        getText : function(){
            return this.initialConfig.text;
        },

        /**
         * Sets the icon CSS class for all components using this action.  The class should supply
         * a background image that will be used as the icon image.
         * @param {String} cls The CSS class supplying the icon image
         */
        setIconClass : function(cls){
            this.initialConfig.iconCls = cls;
            this.callEach('setIconClass', [cls]);
        },

        /**
         * Gets the icon CSS class currently used by all components using this action.
         */
        getIconClass : function(){
            return this.initialConfig.iconCls;
        },

        /**
         * Sets the disabled state of all components using this action.  Shortcut method
         * for {@link #enable} and {@link #disable}.
         * @param {Boolean} disabled True to disable the component, false to enable it
         */
        setDisabled : function(v){
            this.initialConfig.disabled = v;
            this.callEach('setDisabled', [v]);
        },

        /**
         * Enables all components using this action.
         */
        enable : function(){
            this.setDisabled(false);
        },

        /**
         * Disables all components using this action.
         */
        disable : function(){
            this.setDisabled(true);
        },

        /**
         * Returns true if the components using this action are currently disabled, else returns false.
         */
        isDisabled : function(){
            return this.initialConfig.disabled;
        },

        /**
         * Sets the hidden state of all components using this action.  Shortcut method
         * for {@link #hide} and {@link #show}.
         * @param {Boolean} hidden True to hide the component, false to show it
         */
        setHidden : function(v){
            this.initialConfig.hidden = v;
            this.callEach('setVisible', [!v]);
        },

        /**
         * Shows all components using this action.
         */
        show : function(){
            this.setHidden(false);
        },

        /**
         * Hides all components using this action.
         */
        hide : function(){
            this.setHidden(true);
        },

        /**
         * Returns true if the components using this action are currently hidden, else returns false.
         */
        isHidden : function(){
            return this.initialConfig.hidden;
        },

        /**
         * Sets the function that will be called by each component using this action when its primary event is triggered.
         * @param {Function} fn The function that will be invoked by the action's components.  The function
         * will be called with no arguments.
         * @param {Object} scope The scope in which the function will execute
         */
        setHandler : function(fn, scope){
            this.initialConfig.handler = fn;
            this.initialConfig.scope = scope;
            this.callEach('setHandler', [fn, scope]);
        },

        /**
         * Executes the specified function once for each component currently tied to this action.  The function passed
         * in should accept a single argument that will be an object that supports the basic Action config/method interface.
         * @param {Function} fn The function to execute for each component
         * @param {Object} scope The scope in which the function will execute
         */
        each : function(fn, scope){
            Ext.each(this.items, fn, scope);
        },

        // private
        callEach : function(fnName, args){
            var cs = this.items;
            for(var i = 0, len = cs.length; i < len; i++){
                cs[i][fnName].apply(cs[i], args);
            }
        },

        // private
        addComponent : function(comp){
            this.items.push(comp);
            comp.on('destroy', this.removeComponent, this);
        },

        // private
        removeComponent : function(comp){
            this.items.remove(comp);
        },

        /**
         * Executes this action manually using the handler function specified in the original config object
         * or the handler function set with {@link #setHandler}.  Any arguments passed to this
         * function will be passed on to the handler function.
         * @param {Mixed} arg1 (optional) Variable number of arguments passed to the handler function
         * @param {Mixed} arg2 (optional)
         * @param {Mixed} etc... (optional)
         */
        execute : function(){
            this.initialConfig.handler.apply(this.initialConfig.scope || window, arguments);
        }
    };