ChangeWatcher

Pakket	mx.binding.utils
Klasse	public class ChangeWatcher
Overerving	ChangeWatcher Object

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

The ChangeWatcher class defines utility methods that you can use with bindable Flex properties. These methods let you define an event handler that is executed whenever a bindable property is updated.

Meer voorbeelden

Defining binding watchers

Openbare eigenschappen

Overerfde openbare eigenschappen verbergen

Overerfde openbare eigenschappen weergeven

	Eigenschap		Gedefinieerd door
		constructor : Object Verwijzing naar het klasseobject of de constructorfunctie van een bepaalde objectinstantie.	Object
		useWeakReference : Boolean Determines whether the reference to handler is strong or weak.	ChangeWatcher

Openbare methoden

Overerfde openbare methoden verbergen

Overerfde openbare methoden weergeven

	Methode		Gedefinieerd door
		ChangeWatcher(access:Object, handler:Function, commitOnly:Boolean = false, next:ChangeWatcher = null) Constructor.	ChangeWatcher
		canWatch(host:Object, name:String, commitOnly:Boolean = false):Boolean [statisch] Lets you determine if the host exposes a data-binding event on the property.	ChangeWatcher
		getEvents(host:Object, name:String, commitOnly:Boolean = false):Object [statisch] Returns all binding events for a bindable property in the host object.	ChangeWatcher
		getValue():Object Retrieves the current value of the watched property or property chain, or null if the host object is null.	ChangeWatcher
		hasOwnProperty(name:String):Boolean Geeft aan of voor een object een opgegeven eigenschap is gedefinieerd.	Object
		isPrototypeOf(theClass:Object):Boolean Geeft aan of een instantie van de klasse Object zich in de prototypeketen van het object bevindt dat als parameter is opgegeven.	Object
		isWatching():Boolean Returns true if each watcher in the chain is attached to at least one change event.	ChangeWatcher
		propertyIsEnumerable(name:String):Boolean Geeft aan of de opgegeven eigenschap bestaat en kan worden opgesomd.	Object
		reset(newHost:Object):void Resets this ChangeWatcher instance to use a new host object.	ChangeWatcher
		setHandler(handler:Function):void Sets the handler function.	ChangeWatcher
		setPropertyIsEnumerable(name:String, isEnum:Boolean = true):void Stelt de beschikbaarheid van een dynamische eigenschap voor lusbewerkingen in.	Object
		toLocaleString():String Geeft de tekenreeksweergave van dit object weer, geformatteerd volgens de locatiespecifieke conventies.	Object
		toString():String Retourneert een tekenreeksrepresentatie van het opgegeven object.	Object
		unwatch():void Detaches this ChangeWatcher instance, and its handler function, from the current host.	ChangeWatcher
		valueOf():Object Retourneert de primitieve waarde van het opgegeven object.	Object
		watch(host:Object, chain:Object, handler:Function, commitOnly:Boolean = false, useWeakReference:Boolean = false):ChangeWatcher [statisch] Creates and starts a ChangeWatcher instance.	ChangeWatcher

Eigenschapdetails

useWeakReference

eigenschap

public var useWeakReference:Boolean

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

Determines whether the reference to handler is strong or weak. A strong reference (the default) prevents handler from being garbage-collected. A weak reference does not.

De standaardwaarde is false.

Constructordetails

()

Constructor

public function ChangeWatcher(access:Object, handler:Function, commitOnly:Boolean = false, next:ChangeWatcher = null)

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

Constructor. Not for public use. This method is called only from the watch() method. See the watch() method for parameter usage.

Parameters

	`access:Object`

	`handler:Function`

	`commitOnly:Boolean` (default = `false`)

	`next:ChangeWatcher` (default = `null`)

Methodedetails

canWatch

()

methode

public static function canWatch(host:Object, name:String, commitOnly:Boolean = false):Boolean

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

Lets you determine if the host exposes a data-binding event on the property.

NOTE: Property chains are not supported by the canWatch() method. They are supported by the watch() method.

Parameters

	`host:Object` — The host of the property. See the `watch()` method for more information.

	`name:String` — The name of the property. See the `watch()` method for more information.

	`commitOnly:Boolean` (default = `false`) — Set to `true` if the handler should be called only on committing change events. See the `watch()` method for more information.

Geretourneerde waarde

Boolean — true if host exposes any change events on name.

getEvents

()

methode

public static function getEvents(host:Object, name:String, commitOnly:Boolean = false):Object

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

Returns all binding events for a bindable property in the host object.

Parameters

	`host:Object` — The host of the property. See the `watch()` method for more information.

	`name:String` — The name of the property, or property chain. See the `watch()` method for more information.

	`commitOnly:Boolean` (default = `false`) — Controls inclusion of non-committing change events in the returned value.

Geretourneerde waarde

Object — Object of the form { eventName: isCommitting, ... } containing all change events for the property.

getValue

()

methode

public function getValue():Object

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

Retrieves the current value of the watched property or property chain, or null if the host object is null. For example:

      watch(obj, ["a","b","c"], ...).getValue() === obj.a.b.c

Geretourneerde waarde

Object — The current value of the watched property or property chain.

isWatching

()

methode

public function isWatching():Boolean

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

Returns true if each watcher in the chain is attached to at least one change event. Note that the isWatching() method varies with host, since different hosts may expose different change events for the watcher's chosen property.

Geretourneerde waarde

Boolean — true if each watcher in the chain is attached to at least one change event.

reset

()

methode

public function reset(newHost:Object):void

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

Resets this ChangeWatcher instance to use a new host object. You can call this method to reuse a watcher instance on a different host.

Parameters

newHost:Object — The new host of the property. See the watch() method for more information.

setHandler

()

methode

public function setHandler(handler:Function):void

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

Sets the handler function.

Parameters

handler:Function — The handler function. This argument must not be null.

unwatch

()

methode

public function unwatch():void

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

Detaches this ChangeWatcher instance, and its handler function, from the current host. You can use the reset() method to reattach the ChangeWatcher instance, or watch the same property or chain on a different host object.

watch

()

methode

 public static function watch(host:Object, chain:Object, handler:Function, commitOnly:Boolean = false, useWeakReference:Boolean = false):ChangeWatcher

Taalversie:

ActionScript 3.0

Productversie:

Flex 3

Runtimeversies:

Flash Player 9, AIR 1.1

Creates and starts a ChangeWatcher instance. A single ChangeWatcher instance can watch one property, or a property chain. A property chain is a sequence of properties accessible from a host object. For example, the expression obj.a.b.c contains the property chain (a, b, c).

Parameters

	`host:Object` — The object that hosts the property or property chain to be watched. You can use the use the `reset()` method to change the value of the `host` argument after creating the ChangeWatcher instance. The `host` maintains a list of `handlers` to invoke when `prop` changes.

	`chain:Object` — A value specifying the property or chain to be watched. Legal values are: A String containing the name of a public bindable property of the host object. An Object in the form: `{ name: property name, getter: function(host) { return host[name] } }`. The Object contains the name of a public bindable property, and a function which serves as a getter for that property. A non-empty Array containing any combination of the first two options. This represents a chain of bindable properties accessible from the host. For example, to watch the property `host.a.b.c`, call the method as: `watch(host, ["a","b","c"], ...)`. Note: The property or properties named in the `chain` argument must be public, because the `describeType()` method suppresses all information about non-public properties, including the bindability metadata that ChangeWatcher scans to find the change events that are exposed for a given property. However, the getter function supplied when using the `{ name, getter }` argument form described above can be used to associate an arbitrary computed value with the named (public) property.

	`handler:Function` — An event handler function called when the value of the watched property (or any property in a watched chain) is modified. The modification is signaled when any host object in the watcher chain dispatches the event that has been specified in that host object's `[Bindable]` metadata tag for the corresponding watched property. The default event is named `propertyChange`. The event object dispatched by the bindable property is passed to this handler function without modification. By default, Flex dispatches an event object of type PropertyChangeEvent. However, you can define your own event type when you use the `[Bindable]` metadata tag to define a bindable property.

	`commitOnly:Boolean` (default = `false`) — Set to `true` if the handler should be called only on committing change events; set to `false` if the handler should be called on both committing and non-committing change events. Note: the presence of non-committing change events for a property is indicated by the `[NonCommittingChangeEvent(<event-name>)]` metadata tag. Typically these tags are used to indicate fine-grained value changes, such as modifications in a text field prior to confirmation.

	`useWeakReference:Boolean` (default = `false`) — (default = false) Determines whether the reference to `handler` is strong or weak. A strong reference (the default) prevents `handler` from being garbage-collected. A weak reference does not.

Geretourneerde waarde

ChangeWatcher — The ChangeWatcher instance, if at least one property name has been specified to the chain argument; null otherwise. Note that the returned watcher is not guaranteed to have successfully discovered and attached itself to change events, since none may have been exposed on the given property or chain by the host. You can use the isWatching() method to determine the watcher's state.

Verwante API-elementen

mx.events.PropertyChangeEvent

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ChangeWatcher - AS3 Flex

Klassen x

useWeakReference

ChangeWatcher

canWatch

getEvents

getValue

isWatching

reset

setHandler

unwatch

watch