| Language Version: | ActionScript 3.0 |
The Proxy class lets you
override the default behavior of ActionScript operations
(such as retrieving and modifying properties) on an object.
The Proxy class has no constructor, and you should not attempt to instantiate Proxy.
Instead, subclass the Proxy class to override methods such as
getProperty
and provide custom behavior. If you try to use a method of
the Proxy class without overriding the method, an exception is thrown.
And, keep in mind, your own code overriding the methods of the Proxy class can throw
exceptions unintentionally. Throwing exceptions when using these methods causes problems because
the calling code (using operators like
in
,
is
,
delete
and others)
does not expect exceptions. Unless you're already sure your overriding method does not throw exceptions,
Adobe recommends using
try..catch
statements around your implementation of the Proxy class
to avoid fatal errors when operators call your methods. For example:
dynamic class MyProxy extends Proxy {
flash_proxy override function callProperty(name:*, ...rest):* {
try {
// custom code here
}
catch (e:Error) {
// respond to error here
}
}
The Proxy class is a replacement for the
Object.__resolve
and
Object.addProperty
features of ActionScript 2.0, which are no longer
available in ActionScript 3.0. The
Object.addProperty()
feature allowed you to
dynamically create get and set methods in ActionScript 2.0. Although ActionScript 3.0
provides get and set methods at compile time, you cannot dynamically assign one
to an object unless you use the Proxy class.
To avoid collisions with the
public
namespace,
the methods of the Proxy class are in the
flash_proxy
namespace.
Where methods of the Proxy class take a
name
argument,
name
can be either a String or
a QName object (if namespaces are being used).
View the examples
flash_proxy function callProperty(name:*, ... rest):*| Language Version: | ActionScript 3.0 |
Overrides the behavior of an object property that can be called as a function. When a method of
the object is invoked, this method is called. While some objects can be called as functions,
some object properties can also be called as functions.
Parameters
| name:* — The name of the method being invoked. |
| |
| ... rest — An array specifying the arguments to the
called method. |
Returns | * — The return value of the called method. |
See also
flash_proxy function deleteProperty(name:*):Boolean| Language Version: | ActionScript 3.0 |
Overrides the request to delete a property. When a property is deleted
with the
delete
operator, this
method is called to perform the deletion.
Parameters
| name:* — The name of the property to delete. |
Returns | Boolean —
If the property was deleted,
true
; otherwise
false
.
|
See also
flash_proxy function getDescendants(name:*):*| Language Version: | ActionScript 3.0 |
Overrides the use of the
descendant
operator.
When the
descendant
operator is used, this method
is invoked.
Parameters
| name:* — The name of the property to descend
into the object and search for. |
Returns | * —
The results of the
descendant
operator.
|
See also
flash_proxy function getProperty(name:*):*| Language Version: | ActionScript 3.0 |
Overrides any request for a property's value. If the property can't be found, the method
returns
undefined
. For more information on this behavior, see
the ECMA-262 Language Specification, 3rd Edition, section 8.6.2.1.
Parameters
| name:* — The name of the property to retrieve. |
Returns | * —
The specified property or
undefined
if the property is not found.
|
See also
flash_proxy function hasProperty(name:*):Boolean| Language Version: | ActionScript 3.0 |
Overrides a request to check whether an object has a particular property by name.
Parameters
| name:* — The name of the property to check for. |
Returns | Boolean —
If the property exists,
true
; otherwise
false
.
|
See also
flash_proxy function isAttribute(name:*):Boolean| Language Version: | ActionScript 3.0 |
Checks whether a supplied QName is also marked as an attribute.
Parameters
| name:* — The name of the property to check. |
Returns | Boolean —
Returns
true
if the argument for
name
is a QName that is also
marked as an attribute.
|
See also
flash_proxy function nextName(index:int):String| Language Version: | ActionScript 3.0 |
Allows enumeration of the proxied object's properties by index number to
retrieve property names. However, you cannot
enumerate the properties of the Proxy class themselves.
This function supports implementing
for...in
and
for each..in
loops on the object to retrieve the desired names.
For example (with code from
Proxy.nextNameIndex()
):
protected var _item:Array; // array of object's properties
override flash_proxy function nextNameIndex (index:int):int {
// initial call
if (index == 0) {
_item = new Array();
for (var x:* in _target) {
_item.push(x);
}
}
if (index < _item.length) {
return index + 1;
} else {
return 0;
}
}
override flash_proxy function nextName(index:int):String {
return _item[index - 1];
} Parameters
| index:int — The zero-based index value of the object's property. |
Returns | String — String The property's name. |
See also
flash_proxy function nextNameIndex(index:int):int| Language Version: | ActionScript 3.0 |
Allows enumeration of the proxied object's properties by index number. Hhowever, you cannot
enumerate the properties of the Proxy class themselves.
This function supports implementing
for...in
and
for each..in
loops on the object to retrieve property index values.
For example:
protected var _item:Array; // array of object's properties
override flash_proxy function nextNameIndex (index:int):int {
// initial call
if (index == 0) {
_item = new Array();
for (var x:* in _target) {
_item.push(x);
}
}
if (index < _item.length) {
return index + 1;
} else {
return 0;
}
}
override flash_proxy function nextName(index:int):String {
return _item[index - 1];
} Parameters
| index:int — The zero-based index value where the enumeration begins. |
Returns | int — The property's index value. |
See also
flash_proxy function nextValue(index:int):*| Language Version: | ActionScript 3.0 |
Allows enumeration of the proxied object's properties by index number to
retrieve property values. However, you cannot
enumerate the properties of the Proxy class themselves.
This function supports implementing
for...in
and
for each..in
loops on the object to retrieve the desired values.
For example (with code from
Proxy.nextNameIndex()
):
protected var _item:Array; // array of object's properties
override flash_proxy function nextNameIndex (index:int):int {
// initial call
if (index == 0) {
_item = new Array();
for (var x:* in _target) {
_item.push(x);
}
}
if (index < _item.length) {
return index + 1;
} else {
return 0;
}
}
override flash_proxy function nextName(index:int):String {
return _item[index - 1];
} Parameters
| index:int — The zero-based index value of the object's property. |
Returns | * — The property's value. |
See also
flash_proxy function setProperty(name:*, value:*):void| Language Version: | ActionScript 3.0 |
Overrides a call to change a property's value. If the property can't be found, this method
creates a property with the specified name and value.
Parameters
| name:* — The name of the property to modify. |
| |
| value:* — The value to set the property to. |
See also
package {
import flash.display.Sprite;
public class ProxyExample extends Sprite {
public function ProxyExample() {
var arr:ProxyArray = new ProxyArray();
arr.push(1);
arr.push(-2);
arr.push(3);
arr.push(4);
arr.push("five");
trace(arr.length); // 5
trace(arr[0]); // 1
trace(arr[1]); // -2
trace(arr[2]); // 3
trace(arr[3]); // 4
trace(arr.sum()); // 6
arr.clear();
trace(arr); // (empty string)
arr[0] = "zero";
trace(arr); // zero
}
}
}
import flash.utils.Proxy;
import flash.utils.flash_proxy;
dynamic class ProxyArray extends Proxy {
private var _item:Array;
public function ProxyArray() {
_item = new Array();
}
override flash_proxy function callProperty(methodName:*, ... args):* {
var res:*;
switch (methodName.toString()) {
case 'clear':
_item = new Array();
break;
case 'sum':
var sum:Number = 0;
for each (var i:* in _item) {
// ignore non-numeric values
if (!isNaN(i)) {
sum += i;
}
}
res = sum;
break;
default:
res = _item[methodName].apply(_item, args);
break;
}
return res;
}
override flash_proxy function getProperty(name:*):* {
return _item[name];
}
override flash_proxy function setProperty(name:*, value:*):void {
_item[name] = value;
}
}
© 2004-2008 Adobe Systems Incorporated. All rights reserved.
Sun Oct 19 2008, 07:03 PM -07:00 
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