# Class Ext.util.Observable

Package: | Ext.util
Defined In: | Observable-more.js
Class: | Observable
Subclasses: | Component, Direct, History, Resizable, SplitBar, Updater, Connection, DataProxy, Node, Store, Tree, DragTracker, Provider, BasicForm, AbstractSelectionModel, ColumnModel, GridView, PropertyStore, ColumnResizer, Sorter, DefaultSelectionModel, MultiSelectionModel, TreeLoader, ClickRepeater, MixedCollection
Extends: | Object

Base class that provides a common interface for publishing events. Subclasses are expected to to have a property "events" with all the events defined, and, optionally, a property "listeners" with configured listeners defined.
For example:

    Employee = Ext.extend(Ext.util.Observable, {
        constructor: function(config){
            this.name = config.name;
            this.addEvents({
                "fired" : true,
                "quit" : true
            });

            // Copy configured listeners into *this* object so that the base class's
            // constructor will add them.
            this.listeners = config.listeners;

            // Call our superclass constructor to complete construction process.
            Employee.superclass.constructor.call(this, config)
        }
    });

This could then be used like this:

    var newEmployee = new Employee({
        name: employeeName,
        listeners: {
            quit: function() {
                // By default, "this" will be the object that fired the event.
                alert(this.name + " has quit!");
            }
        }
    });

## Config Options

Config Options | Defined By
--- | ---
| listeners : Object A config object containing one or more event handlers to be added to this object during initialization. This should ... A config object containing one or more event handlers to be added to this object during initialization. This should be a valid listeners config object as specified in the addListener example for attaching multiple handlers at once. DOM events from ExtJs Components While some ExtJs Component classes export selected DOM events (e.g. "click", "mouseover" etc), this is usually only done when extra value can be added. For example the DataView's `click` event passing the node clicked on. To access DOM events directly from a Component's HTMLElement, listeners must be added to the Element after the Component has been rendered. A plugin can simplify this step:
    // Plugin is configured with a listeners config object.
    // The Component is appended to the argument list of all handler functions.
    Ext.DomObserver = Ext.extend(Object, {
        constructor: function(config) {
            this.listeners = config.listeners ? config.listeners : config;
        },

        // Component passes itself into plugin's init method
        init: function(c) {
            var p, l = this.listeners;
            for (p in l) {
                if (Ext.isFunction(l[p])) {
                    l[p] = this.createHandler(l[p], c);
                } else {
                    l[p].fn = this.createHandler(l[p].fn, c);
                }
            }

            // Add the listeners to the Element immediately following the render call
            c.render = c.render.createSequence(function() {
                var e = c.getEl();
                if (e) {
                    e.on(l);
                }
            });
        },

        createHandler: function(fn, c) {
            return function(e) {
                fn.call(this, e, c);
            };
        }
    });

    var combo = new Ext.form.ComboBox({

        // Collapse combo when its element is clicked on
        plugins: [ new Ext.DomObserver({
            click: function(evt, comp) {
                comp.collapse();
            }
        })],
        store: myStore,
        typeAhead: true,
        mode: 'local',
        triggerAction: 'all'
    });
| Observable

## Public Properties

This class has no public properties.

## Public Methods

Method | Defined By
--- | ---
| Observable.capture( Observable o, Function fn, [Object scope] ) : void <static> Starts capture on the specified Observable. All events will be passed to the supplied function with the event name + ... <static> Starts capture on the specified Observable. All events will be passed to the supplied function with the event name + standard signature of the event before the event is fired. If the supplied function returns false, the event will not fire. Parameters: `o` : Observable The Observable to capture events from. `fn` : Function The function to call when an event is fired. `scope` : Object (optional) The scope (`this` reference) in which the function is executed. Defaults to the Observable firing the event. Returns: void | Observable
| Observable.observeClass( Function c, Object listeners ) : void <static> Sets observability on the passed class constructor. This makes any event fired on any instance of the passed class al... <static> Sets observability on the passed class constructor. This makes any event fired on any instance of the passed class also fire a single event through the class allowing for central handling of events on many instances at once. Usage:
    Ext.util.Observable.observeClass(Ext.data.Connection);
    Ext.data.Connection.on('beforerequest', function(con, options) {
        console.log('Ajax request made to ' + options.url);
    });
Parameters: `c` : Function The class constructor to make observable. `listeners` : Object An object containing a series of listeners to add. See addListener. Returns: void | Observable
| Observable.releaseCapture( Observable o ) : void <static> Removes all added captures from the Observable. <static> Removes all added captures from the Observable. Parameters: `o` : Observable The Observable to release Returns: void | Observable
- | addEvents( Object|String o, string Optional. ) : void Adds the specified events to the list of events which this Observable may fire. Adds the specified events to the list of events which this Observable may fire. Parameters: `o` : Object|String Either an object with event names as properties with a value of `true` or the first event name string if multiple event names are being passed as separate parameters. `Optional.` : string Event name if multiple event names are being passed as separate parameters. Usage:
      this.addEvents('storeloaded', 'storecleared');
Returns: void | Observable
- | addListener( String eventName, Function handler, [Object scope], [Object options] ) : void Appends an event handler to this object. Appends an event handler to this object. Parameters: `eventName` : String The name of the event to listen for. `handler` : Function The method the event invokes. `scope` : Object (optional) The scope (`this` reference) in which the handler function is executed. If omitted, defaults to the object which fired the event. `options` : Object (optional) An object containing handler configuration. properties. This may contain any of the following properties: scope : Object The scope (`this` reference) in which the handler function is executed. If omitted, defaults to the object which fired the event. delay : Number The number of milliseconds to delay the invocation of the handler after the event fires. single : Boolean True to add a handler to handle just the next firing of the event, and then remove itself. buffer : Number Causes the handler to be scheduled to run in an Ext.util.DelayedTask delayed by the specified number of milliseconds. If the event fires again within that time, the original handler is not invoked, but the new handler is scheduled in its place. target : Observable Only call the handler if the event was fired on the target Observable, not if the event was bubbled up from a child Observable. Combining Options Using the options argument, it is possible to combine different types of listeners: A delayed, one-time listener.
      myDataView.on('click', this.onClick, this, {
      single: true,
      delay: 100
      });
  Attaching multiple handlers in 1 call The method also allows for a single argument to be passed which is a config object containing properties which specify multiple handlers.
      myGridPanel.on({
      'click' : {
          fn: this.onClick,
          scope: this,
          delay: 100
      },
      'mouseover' : {
          fn: this.onMouseOver,
          scope: this
      },
      'mouseout' : {
          fn: this.onMouseOut,
          scope: this
      }
      });
  Or a shorthand syntax:
      myGridPanel.on({
      'click' : this.onClick,
      'mouseover' : this.onMouseOver,
      'mouseout' : this.onMouseOut,
       scope: this
      });
Returns: void | Observable
| enableBubble( String/Array events ) : void Enables events fired by this Observable to bubble up an owner hierarchy by calling this.getBubbleTarget() if present.... Enables events fired by this Observable to bubble up an owner hierarchy by calling `this.getBubbleTarget()` if present. There is no implementation in the Observable base class. This is commonly used by Ext.Components to bubble events to owner Containers. See Ext.Component.getBubbleTarget. The default implementation in Ext.Component returns the Component's immediate owner. But if a known target is required, this can be overridden to access the required target more quickly. Example:
    Ext.override(Ext.form.Field, {
        //  Add functionality to Field's initComponent to enable the change event to bubble
        initComponent : Ext.form.Field.prototype.initComponent.createSequence(function() {
            this.enableBubble('change');
        }),

        //  We know that we want Field's events to bubble directly to the FormPanel.
        getBubbleTarget : function() {
            if (!this.formPanel) {
                this.formPanel = this.findParentByType('form');
            }
            return this.formPanel;
        }
    });

    var myForm = new Ext.formPanel({
        title: 'User Details',
        items: [{
            ...
        }],
        listeners: {
            change: function() {
                // Title goes red if form has been modified.
                myForm.header.setStyle('color', 'red');
            }
        }
    });
Parameters: `events` : String/Array The event name to bubble, or an Array of event names. Returns: void | Observable
| fireEvent( String eventName, Object... args ) : Boolean Fires the specified event with the passed parameters (minus the event name). An event may be set to bubble up an Obse... Fires the specified event with the passed parameters (minus the event name). An event may be set to bubble up an Observable parent hierarchy (See Ext.Component.getBubbleTarget) by calling enableBubble. Parameters: `eventName` : String The name of the event to fire. `args` : Object... Variable number of parameters are passed to handlers. Returns: `Boolean` returns false if any of the handlers return false otherwise it returns true. | Observable
| hasListener( String eventName ) : Boolean Checks to see if this object has any listeners for a specified event Checks to see if this object has any listeners for a specified event Parameters: `eventName` : String The name of the event to check for Returns: `Boolean` True if the event is being listened for, else false | Observable
| on( String eventName, Function handler, [Object scope], [Object options] ) : void Appends an event handler to this object (shorthand for addListener.) Appends an event handler to this object (shorthand for addListener.) Parameters: `eventName` : String The type of event to listen for `handler` : Function The method the event invokes `scope` : Object (optional) The scope (`this` reference) in which the handler function is executed. If omitted, defaults to the object which fired the event. `options` : Object (optional) An object containing handler configuration. Returns: void | Observable
| purgeListeners() : void Removes all listeners for this object Removes all listeners for this object Parameters: None. Returns: void | Observable
| relayEvents( Object o, Array events ) : void Relays selected events from the specified Observable as if the events were fired by this. Relays selected events from the specified Observable as if the events were fired by `this`. Parameters: `o` : Object The Observable whose events this object is to relay. `events` : Array Array of event names to relay. Returns: void | Observable
| removeListener( String eventName, Function handler, [Object scope] ) : void Removes an event handler. Removes an event handler. Parameters: `eventName` : String The type of event the handler was associated with. `handler` : Function The handler to remove. This must be a reference to the function passed into the addListener call. `scope` : Object (optional) The scope originally specified for the handler. Returns: void | Observable
| resumeEvents() : void Resume firing events. (see suspendEvents) If events were suspended using the queueSuspended parameter, then all event... Resume firing events. (see suspendEvents) If events were suspended using the `queueSuspended` parameter, then all events fired during event suspension will be sent to any listeners now. Parameters: None. Returns: void | Observable
| suspendEvents( Boolean queueSuspended ) : void Suspend the firing of all events. (see resumeEvents) Suspend the firing of all events. (see resumeEvents) Parameters: `queueSuspended` : Boolean Pass as true to queue up suspended events to be fired after the resumeEvents call instead of discarding all suspended events; Returns: void | Observable
| un( String eventName, Function handler, [Object scope] ) : void Removes an event handler (shorthand for removeListener.) Removes an event handler (shorthand for removeListener.) Parameters: `eventName` : String The type of event the handler was associated with. `handler` : Function The handler to remove. This must be a reference to the function passed into the addListener call. `scope` : Object (optional) The scope originally specified for the handler. Returns: void | Observable

## Public Events

This class has no public events.