ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Using native JSON functionality
Parsing example
The following example shows a strategy for reviving objects parsed from JSON strings. This example defines two
classes: JSONGenericDictExample and JSONDictionaryExtnExample. Class JSONGenericDictExample is a custom
dictionary class. Each record contains a person’s name and birthday, as well as a unique ID. Each time the
JSONGenericDictExample constructor is called, it adds the newly created object to an internal static array with a
statically incrementing integer as its ID. Class JSONGenericDictExample also defines a revive() method that extracts
just the integer portion from the longer id member. The revive() method uses this integer to look up and return the
correct revivable object.
Class JSONDictionaryExtnExample extends the ActionScript Dictionary class. Its records have no set structure and
can contain any data. Data is assigned after a JSONDictionaryExtnExample object is constructed, rather than as classdefined
properties. JSONDictionaryExtnExample records use JSONGenericDictExample objects as keys. When a
JSONDictionaryExtnExample object is revived, the JSONGenericDictExample.revive() function uses the ID
associated with JSONDictionaryExtnExample to retrieve the correct key object.
Most importantly, the JSONDictionaryExtnExample.toJSON() method returns a marker string in addition to the
JSONDictionaryExtnExample object. This string identifies the JSON output as belonging to the
JSONDictionaryExtnExample class. This marker leaves no doubt as to which object type is being processed during
JSON.parse().
package {
// Generic dictionary example:
public class JSONGenericDictExample {
static var revivableObjects = [];
static var nextId = 10000;
public var id;
public var dname:String;
public var birthday;
}
}
public function JSONGenericDictExample(name, birthday) {
revivableObjects[nextId] = this;
this.id = "id_class_JSONGenericDictExample_" + nextId;
this.dname = name;
this.birthday = birthday;
nextId++;
}
public function toString():String { return this.dname; }
public static function revive(id:String):JSONGenericDictExample {
var r:RegExp = /^id_class_JSONGenericDictExample_([0-9]*)$/;
var res = r.exec(id);
return JSONGenericDictExample.revivableObjects[res[1]];
}
package {
import flash.utils.Dictionary;
import flash.utils.ByteArray;
// For this extension of dictionary, we serialize the contents of the
// dictionary by using toJSON
public final class JSONDictionaryExtnExample extends Dictionary {
public function toJSON(k):* {
var contents = {};
for (var a in this) {
Last updated 6/6/2012
121