This is a pretty basic question and I'm sure there's an answer somewhere but for the life of me I can't find it. Anyways, I had a lot of variables of a new instance of an object to change and, for fun mostly, I thought I'd try and shorten the syntax or chain it together. But I can't. Here's some example code:
var text = new TextObjectThing(0, 0, 500, "Text");
text.color = 0xFFFFFFFF;
text.size = 26;
text.scrollFactor.x = 0;
text.scrollFactor.y = 0;
as you can see you have to do that "text.property" thing several times. This is fine in a practical sense, but I was just wondering if anyone knew how to re-organise that a bit.
EDIT: I guess this would be important if you wanted/needed to have an anonymous object for some reason. You can't set those variables like that if it's anonymous.
You can use a trick to chain call without modify your Object :
var shape : Shape = new Shape;
// Chain property init
Initializer.init(shape).x(100).y(100).alpha(.5);
// Chain function call
Initializer.init(shape.graphics).beginFill( 0xFF0000 ).drawCircle( 100, 100, 50).endFill().beginFill( 0xFFFFFF ).drawCircle( 100, 100, 10).endFill();
addChild(shape);
And the initializer class :
package
{
import flash.utils.Proxy;
import flash.utils.flash_proxy;
public dynamic class Initializer extends Proxy
{
// To avoid new instance
private static var _instance : Initializer = new Initializer(null);;
// Current target Object
private var _target : Object;
// Constructor
public function Initializer(target : Object){
_target = target;
}
// Call it to avoid new Initizer instance
public static function init(target : Object) : Initializer{
_instance._target = target;
return _instance;
}
// Catch function call and return initializer to chain call
override flash_proxy function callProperty(name:*, ... rest):* {
if(_target)
{
// Emulate function setter
if(_target.hasOwnProperty(name) && !(_target[name] is Function))
_target[name] = rest[0];
// If not a property, call as a classic function
else
_target[name].apply(_target, rest);
}
return this;
}
}
}
It is just for fun because proxy call add a very small time for each call, if you want to use it very very often (ex: 10000 per frame), it will be faster to use classic approach.
You can also use "with" keyword like (please note the ; char after constructor):
var tf : TextField = new TextField(); with(tf) {
text = "Hello";
alpha = .5;
setTextFormat( new TextFormat( "Verdana", 16, 0xFF0000) );
}
Or chain when values are the same :
var text = new TextObjectThing(0, 0, 500, "Text");
text.scrollFactor.x = text.scrollFactor.y = 0;
If you make methods return this, you can chain it.
public method setColor(hex:uint):this
public method setSize(size:Number):this
and then you can make
text.setColor(0xFFFFFF).setSize(26);
you can also make one method that will take many arguments, and to leave the default arguments unchanged
You can organize the relative properties together as a new data struct.
For example flash.text.TextFormat. It contains the properties could be used in text.
You could pass the data struct object instead of several separate properties.It will make your code more simple and clearer. For example, you want to copy same text style for from another text, you just need to get the textFormat of target text and set it to your text.
Related
I want to know whether in ActionScript 3 there's a way to share a same function (method) between the instances of a class definition, only referencing the same function everytime... i.e., this example should log true, but logged false (note: I'd want this to reduce duplicating functions).
class A {
function f() {}
}
trace(
(new A).f === (new A).f
)
An ActionScript 3 language specification appears to say that a prototype attribute exists, but not implemented. I've understood that individual classes have a prototype object. I've specially found a prototype property (probably inherited from Class/Object) and wonder if classes use meta functions in order to be constructed (since their type is "object"... when I test with typeof: trace(typeof A, typeof Class, typeof Object)).
My last try:
class A {}
A.prototype.f = function() {}
trace(
(new A).f === (new A).f
)
It says that f doesn't exist. I could define this class as a function instead (in order to move methods to the prototype object):
function A() {}
A.prototype.f = function() {}
, but in this way I can't control access of instance members.
AS3 uses Bound methods to ensure that inside your functions, this always points to original instance object by default.
Imagine that you pass a function f of an instance a to some other object b. When then object b calls function f, the this name still points to a inside scope of the function - this reference has to be store somewhere.
Well, you could assign function to static property of your class:
package adnss.projects.evTest
{
public class A {
private var x:Number = 5;
private var _y:Number = 0;
public function A(){}
static public const f = function (p:Number):Number {
this._y = p;
return this.x*p;
}
public function get y():Number { return _y; }
}
}
And then have access to private properties of the instance of A in that static function by explicitly using this:
var instance:A = new A();
trace("return:", A.f.call(instance, 3)); //return: 15
trace("instace:", instance.y); //instance: 3
But that is kind of tricky for possible benefits (if any).
And about prototypes. You basically don't use them in AS3. Is't there like a souvenir :) - read this for more info
So, i've been working with ByteArrays a lot recently and i'm running into some annoying problems that make me want to rip my hair out.
basically, i'm trying to save project data for an application that i'm making to compile characters for a game into one file. the project consists of custom objects, vectors, vectors of vectors, and even vectors of vectors of custom objects! i figured the best way to write all this data properly would be to use the IExternalizable interface with the readExternal and writeExternal commands. so here's what i'm doing.
i write all the project data to an object, then write that object into a ByteArray, and save it to a file:
// probject means project object !
mProbject= { };
// Register vector as class, just to prevent any errors about that just in case
registerClassAlias("vec_core.timeline.KeyFrame", Vector.<KeyFrame> as Class);
// single KeyFrame Object
mProbject.currentFrame = Main.getInstance().animationList.selectedItem.currentKeyFrame;
// a Vector.<Vector.<KeyFrame>>
mProbject.frames = Main.getInstance().animationList.keyFrameVectorVector;
// an unsigned int
mProbject.selectedItemIndex = Main.getInstance().animationList.entries.indexOf(Main.getInstance().animationList.selectedItem);
// Vector.<String>
mProbject.animationNames = Main.getInstance().animationList.animationNames;
// String
mProbject.projectPath = nativePath;
//String
mProbject.projectName = name;
mByteArray = new ByteArray();
mByteArray.writeObject(mProbject);
mByteArray.compress();
return mByteArray;
inside the KeyFrame class though, there is two more vectors of custom objects:
private var mHitboxes:Vector.<Hitbox>;
private var mHitboxSprites:Vector.<HitboxSprite>;
so i set up both of those classes and my KeyFrame class to use IExternalizable:
public class HitboxSprite extends Sprite implements IExternalizable
{
public function readExternal(input:IDataInput):void
{
trueBounds.x = input.readFloat();
trueBounds.y = input.readFloat();
trueBounds.width = input.readFloat();
trueBounds.height = input.readFloat();
mHitbox = input.readObject();
}
public function writeExternal(output:IDataOutput):void
{
output.writeFloat(trueBounds.x);
output.writeFloat(trueBounds.y);
output.writeFloat(trueBounds.width);
output.writeFloat(trueBounds.height);
output.writeObject(mHitbox);
}
}
public class Hitbox implements IExternalizable
{
public function readExternal(input:IDataInput):void
{
mName = input.readUTF();
mType = input.readUnsignedInt();
mEnabled = input.readBoolean();
mKnockback = input.readBoolean();
x = input.readFloat();
y = input.readFloat();
width = input.readFloat();
height = input.readFloat();
addMultipleTags(input.readUTF());
}
public function writeExternal(output:IDataOutput):void
{
output.writeUTF(mName);
output.writeUnsignedInt(mType);
output.writeBoolean(mEnabled);
output.writeBoolean(mKnockback);
output.writeFloat(mX);
output.writeFloat(mY);
output.writeFloat(mWidth);
output.writeFloat(mHeight);
output.writeUTF(getAllTags());
}
}
public class KeyFrame implements IExternalizable
{
public function readExternal(input:IDataInput):void
{
mID = input.readUnsignedInt();
mLabel = input.readUTF();
}
public function writeExternal(output:IDataOutput):void
{
output.writeUnsignedInt(mID);
output.writeUTF(mLabel);
}
}
but when it gets to the writeObject() method of the "root" ByteArray, i get the error:
[Fault] exception, information=ArgumentError: Error #2004: One of the parameters is invalid.
this is probably the single most annoying problem i've ever had. it seems like i've tried everything and nothing is working.
does anyone else have experience with this? am i doing something wrong??
i'd appreciate any help i can get on this. i just wanna continue making my game :<
Like mentioned in the comment section, you were looking for this. What rang the bell for me was the "Sprite" class you extended. That made me suspicious in the matter that you were trying to externalize visualizable content.
This is a hard question to do, but I'll try to explain.
I have the Class and the parameters of its contructor as an object. What I need to do is a function that returns an instance of this class, passing this parameters to the constructor.
This is the code:
Some random and unmodifiable class:
public Foo {
public function Foo(a:int, b:String) {
// constructor
}
}
And some function (in some another class):
function bar(params:Object):* {
var baz:Foo = new Foo(params.a, params.b);
return baz;
}
What I need to do is make this function generic, without pass params as parameter to Foo constructor because I can't modify it. Something like:
function bar2(clazz:Class, params:Object):* {
var baz:* = new clazz(/*some magic way to transform params in comma separated parameters*/);
return baz;
}
Anyone can help me?
Thanks a lot.
This is called parameterized factory. First I thought about Function.apply, but it doesn't apply to constructors (he-he). So, people are making factories like this:
function create(what:Class, args:Array):* {
switch (args.length) {
case 0: return new what();
case 1: return new what(args[0]);
case 2: return new what(args[0], args[1]);
...
//PROFIT!
}
throw new Error("Need moar cases!");
}
what about using ByteArrayto copy the object ?
function clone(source:Object):* {
var copier:ByteArray = new ByteArray();
copier.writeObject(source);
copier.position = 0;
return(copier.readObject());
}
newObjectCopy = clone(originalObject);
source
If you have the option of not using a constructor, but adding an initialise() function to each class which can be constructed instead, you could use Function.apply - something like in the example below.
public class ThingCreator
{
public static function createTheThing(c:Class, params:Array):Object
{
var the_thing:Object = new c();
the_thing.initialise.apply(the_thing, params);
return the_thing;
}
}
As alxx pointed out above, Function.apply and AS3 reflection in this case does not seem to work with AS3's constructors.
If an AS3 method returns a reference to a complex type, is there any way to make that 'readonly', like how you can have const member functions in C++? An architecture I want to use calls for a class building itself from a passed template object... and really the template object should not be modifiable. I'm currently forced to add call-back enumerators and/or lots of extra accessor methods.
Flex has an ObjectUtil.clone() method that will make a deep copy. The copy will still by modifiable, but since it's a copy, the changes won't propagate back to the original.
The method is no complicated so if you're not using Flex, just add this to a util class:
public static function copy(value:Object):Object
{
var buffer:ByteArray = new ByteArray();
buffer.writeObject(value);
buffer.position = 0;
var result:Object = buffer.readObject();
return result;
}
There is no way to do that in AS3, there is Sam's way of doing it, but it still requires copying that object before you return it, depending on the complexity of that object, it can impact the performance.
Immutable interfaces are a near-equivillant to const-correctness. Here's an example:
interface CPoint {
function get x():Number;
function get y():Number;
}
class Point implements CPoint {
private var _x:Number;
private var _y:Number;
public function get x():Number { return _x; }
public function get y():Number { return _y; }
public function set x(val:Number) { _x = val; }
public function set y(val:Number) { _y = val; }
public function normalize():void {
var length:Number = Math.sqrt(_x*_x + _y*_y);
_x /= length;
_y /= length;
}
public function Point(x:Number, y:Number) {
_x = x; _y = y;
}
}
If you return a Point as a CPoint reference, then its fields cannot be altered. You can do an explicit cast to a Point from a CPoint to force access, but you can do the same thing with const casting in C++.
Unfortunately, AS3 doesn't support covariance like it should, so things get unnecessarily difficult for const sub-objects. For example, if you had a Line class that was made up of two points, you might want to say line.start.x = 47; if you have full access to the line, but allow reading of line.start.x through an immutable interface. You could do this if there was covariance, but instead you'll need to add separate get properties for mutable and immutable properties. So, you'd end up instead with line.cstart.x for reads from a CLine. Something like this:
interface CLine {
function get cstart():CPoint;
function get cend():CPoint;
}
class Line implements CLine {
private var _end:Point;
private var _start:Point;
public function get cend():CPoint { return _end; }
public function get cstart():CPoint { return _start; }
public function get end():Point { return _end; }
public function get start():Point { return _start; }
public function Line(x1:Number, y1:Number, x2:Number, y2:Number) {
_start = new Point(x1, y1);
_end = new Point(x2, y2);
}
}
I would create a flash.utils.proxy object. You could create a proxy object that has read only implementation of a child that is passed in.
Here is the documentation for creating a proxy object. http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/flash/utils/Proxy.html
Note: Proxy is pretty damn slow, since you'll be bypassing native object checking, and replacing it with a function call -- which when using a lot will be slow. I would do some simple performance testing first.
note: This is pseudo-code.
use namespace flash_proxy;
dynamic class ReadOnly extends flash.utils.Proxy {
private var target:Object;
public function ReadOnly(target:Object) {
this.target = target;
}
flash_proxy function getProperty(name:*):*
return target[name];
}
flash_proxy function setProperty(name:*, value:*):void
// throw an error or do nothing
}
}
You could then do:
var readOnly:ReadOnly = new ReadOnly(stage.loaderInfo.parameters);
readOnly.someparameter = 'newvalue';
trace(readOnly.someparameter); // should be old value
Ok here is what I am currently trying to do. I have a class called vdata.as which takes 2 paramaters both are strings sent from the main stage. Parameter one is the location for an XML file that I need to open and read. The second parameter is the name of the video I am currently looking for.
Now I can get the data from the XML file and display it with out any issue if its called from my class but when I try to access any of it from the stage I get undefined.
import flash.net.*;
import flash.display.*;
import flash.events.*;
public class videoData
{
private var mName:String;
private var mLink:String;
private var mCategory:String;
public static var elementArray:Array;
// Constructor
public function videoData(xmlPath:String,xmlVidSrc:String,pMC:MovieClip)
{
pXmlPath = xmlPath;
pXmlVidSrc = xmlVidSrc;
xmlloader = new URLLoader();
elementArray = new Array();
}
public function getXML()
{
XMLData();
}
private function XMLData()
{
xmlloader.load(new URLRequest(pXmlPath));
xmlloader.addEventListener(Event.COMPLETE,parseXMLData);
}
private function parseXMLData():void
{
var x:XML = new XML(xmlloader.data);
Init(x);
}
private function Init(m:XML):*
{
var i:Number;
for(i=0; i<m.videos.videoname.length(); i++)
{
if(m.videos.videoname[i].#name == pXmlVidSrc)
{
videoData.elementArray.push(m.videos.videoname[i].#name);
videoData.elementArray.push(m.videos.videoname[i].#category);
videoData.elementArray.push(m.videos.videoname[i].link.#url);
}
}
}
}
When I call it from the main stage the code is as follows.
var xData:videoData = new videoData(xmlPath,vidSrc,this);
xData.getXML();
then when I try to access any elements of videoData.elementArray they come up undefined...
Im just smacking my head on my desk trying to figure this out any help would be great.
Why is elementArray a static var, you only need to make it public to use it outside the function.
I'm quite confusing but you may want to try a debugging tool like "De MonsterDebugger", I would start by tracing xmlloader.data in the parseXMLData function.
"addEventListener" doesn't "fire"...the event does. You'll need to add a boolean to state for the stage that elementArray has been populated and set that after the init function.
Is elementArray something that needs to be true across all instances of videoData? If not, it shouldn't be static. You can use MovieClip(this.root).xData to access that instance of the video class from one of your other classes.
If the event has completed and the array is still empty - then it wasn't populated by your parser. You can also do checks to see if the elementArray.length > 0.
EDIT in response to comment:
as a public member or preferably a read-only property make a boolean variable:
var parseComplete:Boolean;
Set it to false in your constructor.
Then, after your call to "Init" in your Event.COMPLETE callback set:
parseComplete=true;
Then make sure parseComplete == true before you ever access elementArray. If you're waiting for the parser to complete you might want to set a timeout or some sort of try/catch mechanism just in case there are any unforeseen errors that would cause some sort of:
while( !xData.parseComplete ) { }
To loop indefinitely. It all depends on the usage. Personally I'd probably add a callback from the event listener to the stage to trigger whatever is supposed to happen next.