The task was meant to be quite simple: I needed to initialize variable with new keyword dynamically, depending on it's type. For example:
public var object:Sprite;
...
object = new Sprite();
In this case type is Sprite, but it could be anything and a method which actually instantiates it with new, doesn't know with what type it was declared. Of course I could store type (or class name) in string variable and instantiate object with it. But I just wonder if I could get that type info from the object itself, 'cause it's declared in a class and logically thinking it's type info might be stored somewhere and be retrievable.
Yes, you can, but the variable must be public (or have accessor methods), and you need its name as a String:
Use describeType() to get an XML Description of your class, then get accessors and variables as XMLList, iterate until you find your variable's name, and get the class by calling getDefinitionByName(). Here's an example:
var className : String = "";
var type:XML = describeType (this);
var variables:XMLList = type..variable;
for each (var variable:XML in variables) {
if (variable.#name == myVariableName) {
className = variable.#type;
break;
}
}
if (className == "") {
var accessors:XMLList = type..accessor;
for each (var accessor:XML in accessors) {
if (accessor.#name == myVariableName) {
className = accessor.#type;
break;
}
}
}
if (className=="") {
trace ("no such variable");
return;
}
var ClassReference : Class = getDefinitionByName( className.replace ("::", ".") ) as Class;
myVariable = new ClassReference( );
I can't figure out how to "reply" to an answer, otherwise I would add this to the current top answer.
If you have a list of known types that the object could be, you could test against those types using typeof.
switch(typeof unknownVar)
{
case typeof Function:
unknownVar = new Function();
break;
case typeof String:
unknownVar = "Bruce Lee";
break;
case typeof Number:
unknownVar = 3.14;
break;
default:
trace(typeof unknownVar); // This is not normally helpful...
}
In short no, you can't get the type of an uninitialised variable.
Sounds like this is kind of a factory pattern implementation. Your best bet is to pass a reference of the Class to the method
method:
public function create(class:Class) : void
{
return new class();
}
calling code:
public var object:Sprite;
...
object = createObject(Sprite)
Related
When using ObjectUtil there is a method called, toString() that takes an object. If you pass it a class named, "Person" it will return the string "[class Person]".
var person:Person = new Person();
trace(ObjectUtil.toString(person));//UPDATE I'm not using ObjectUtil.toString()
// traces [class Person]
Is there a toObject() method? Something that takes the same format toString outputs and creates an instance like so:
var person:Person = ObjectUtil.toObject("[class Person]");
UPDATE:
Sorry. This is incorrect. I thought I was using ObjectUtil.toString(). I was not. When I use that method it returns something like:
(com.printui.assets.skins::fontList)#0
accessibilityDescription = ""
accessibilityEnabled = true
accessibilityImplementation = (null)
In my code somewhere it is returning "[class Person]" like I was described. This is the line:
var currentValue:* = target[property];
popUpValueInput.text = currentValue;
I thought it was using instance.toString() but toString() is not returning anything close to that:
var f:fontList = new fontList();
var f1:fontList = new fontList();
trace("" + f);
trace("" + f1);
trace(f1.toString());
Results in:
fontList2
fontList5
fontList5
In general you should do this:
In your Person class add this method:
public function toString():String
{
return "Person" ;
}
So to make an instance of the class by name use this code:
var p = new (getDefinitionByName( ObjectUtils.toString(person)))
or it can be used a regex in general for all classes (thanks to 1.21 gigawatts ):
var p = new (getDefinitionByName( ObjectUtil.toString(Person).match(/\((.*)\)/)[1] ) );
So im creating something that now is finished and i want not to create every time elements, but to Pool them (ObjectPooling)
The problem comes that my object from the pool doesnt have the variable from the class it mimics, or at least i understand it that way, cause it doesnt do what it should.
Can someone tell me does this
var myNewBox:Box = Pool_myBox.getSprite() as Box;
mean that all the proparties and parameters that the class Box() has will be given and can be used by the new variable myNewBox or it`s a little more tricky that this?
or in other words is var myNewBox:Box = new Box();
the same as
var myNewBox:Box = Pool_myBox.getSprite() as Box;
------------EDIT-----------
so i do private var Pool_myBox:SpritePool; in the Main Class .
and set Pool_myBox = new SpritePool(Bullet,20); so in the 1st moment it has generated 20 objects.
The whole SpritePool class is this
package {
import flash.display.DisplayObject;
public class SpritePool {
private var pool:Array;
private var counter:int;
private var classRef:Class;
public function SpritePool(type:Class, len:int) {
pool = new Array();
counter = len;
classRef = type;
var i:int = len;
while (--i > -1) {
pool[i] = new type();
}
}
public function getSprite():DisplayObject {
if (counter > 0) {
return pool[--counter];
} else {
increasePool(10);
return getSprite();
}
}
public function increasePool(amount:int):void {
counter += amount;
while( --amount > -1 )
pool.unshift ( new classRef() );
}
public function returnSprite(s:DisplayObject):void {
pool[counter++] = s;
//trace(pool.length)
}
}
}
Absolutely not. If your getSprite() method does not return a Box instance (or some descendant of it), it will not 'inherit' the properties of Box. as is not performing any kind of internal magic - it is simply casting and telling the compiler that you know what you are doing and that the object indeed is a XXX instance (fill in). You should use casting only when going from a more general type to a more specific type, let's assume this:
var child:Sprite = parent.getChildAt(0); //what does this return? A display object instance => compiler will throw an error as Sprite is not DisplayObject
/*
Implicit coercion of a value with static type flash.display:DisplayObject to a possibly unrelated type flash.display:Sprite.
*/
//so you cast it:
var child:Sprite = parent.getChildAt(0) as Sprite; //this won't throw anything cos you casted it correctly
Also note that:
myObj as MyObj
is the same as:
MyObj(myObj)
if Pool_myBox.getSprite returns only Box objects, then you don't need to cast. The getSprite function should be look something like:
public function getSprite():Box {
var recycled_box:Box = ... // get box from pool
return recycled_box;
}
var myNewBox = Pool_myBox.getSprite();
Then, myNewBox will look and act like a Box. Note that any initialization or processing that happened on previous Box instances must be undone when it's returned to the pool if you need a "fresh" instance of Box.
OK, given the pool class, it looks like it should work with casting. Note that your text says you're passing in "Bullet" as the Class, while your code seems to want Box's (I assume this is either a typo, or Bullet is a superclass of Box?). If it works on the first 20, but not after you start recycling, then check what may need to be undone (as above).
What behavior are you seeing that makes you think it's not returning the right Class?
The Ancestor class does, indeed, have a function called (for the sake of example) "foo".
public static function callAncestorStaticMethod() : void
{
var ancestorClassName : String = getQualifiedSuperclassName(Descendant);
var ancestorClass : Class = Class(getDefinitionByName(ancestorClassName));
ancestorClass.foo(); // <---- runtime error here: foo is not a function
}
Examining ancestorClass finds it an Object with no visible properties (ancestorClass.prototype does not either).
So, how do I call a static function on a class when I only have its name as a string at runtime ?
I was able to call a static function in the superclass using the following code:
var c:ChildClass = new ChildClass();
var s:String = getQualifiedSuperclassName(c);
var cl:Class = getDefinitionByName(s) as Class;
cl.foo.call();
//cl["foo"].call();
A Class object has all of the static properties and methods of the Class, so this should be reliable. cl.foo returns a Function object that you can then .call().
You can get a reference to the instance's own class using the constructor property, but to access the ancestor classes, you have to use describeType and getDefinitionByName. These are powerful, but costly - so make sure you don't overuse this:
function callStaticAncestorProperty( instance:Object, staticProperty:String ):* {
var type:XML = describeType( instance );
var ret:* = instance.constructor[staticProperty];
for each(var extend:XML in type.extendsClass)
ret = ret ? ret : getStaticPropertyOrUndefined( extend, staticProperty );
return ret;
}
function getStaticPropertyOrUndefined( extend:XML, staticProperty:String ):* {
var clazz:Class = getDefinitionByName( extend.#type.toString().replace( "::", "." ) ) as Class;
return clazz[staticProperty] ? clazz[staticProperty] : undefined;
}
This checks if the class itself has the property, and then iterates over each super type. Note that the first value to be found will be returned, i.e. if both the subclass and a super class have this property, that of the subclass will be returned.
Edit
I only just realized you were asking about method calls, not properties. That works pretty much the same way:
function callStaticAncestorMethod( instance:Object, staticMethod:String ):void {
var type:XML = describeType( instance );
var method:Function = instance.constructor[staticMethod];
for each(var extend:XML in type.extendsClass)
method = method ? method : getStaticMethodOrUndefined( extend, staticMethod );
if (method) method();
}
function getStaticMethodOrUndefined( extend:XML, staticMethod:String ):Function {
var clazz:Class = getDefinitionByName( extend.#type.toString().replace( "::", "." ) ) as Class;
return clazz[staticMethod] ? clazz[staticMethod] : undefined;
}
Or (Based on Sam DeHaan answer's):
If Superclass and Descendant have both a String id property...
(getDefinitionByName(getQualifiedSuperclassName(Descendant))as Class).foo();
trace((getDefinitionByName(getQualifiedSuperclassName(Descendant))as Class).id);
Where :
// trace (Descendant.id);
// if private : compile time Error.
// 1178: Attempted access of inaccessible property id through a reference with static type Class.
var d:Descendant;
trace((getDefinitionByName("Descendant") as Class).id);
// output undefined if private : the value if public. But don't throw compile time Error.
(getDefinitionByName("Descendant") as Class).foo();
// Call static foo() from Descendant. // Throw a compile time Error if method is private
// trace (Superclass.id);
// if private : compile time Error.
// 1178: Attempted access of inaccessible property id through a reference with static type Class.
var s:Superclass;
trace((getDefinitionByName("Superclass") as Class).id);
// output undefined if private : the value if public. But don't throw compile time Error.
(getDefinitionByName("Superclass") as Class).foo();
// Call static foo() from Superclass. // Throw a compile time Error if method is private
I have a game with a variety of ship types. My Ship class has a static array holding one of each of the types in it. Whenever I make a new Ship (other than when initializing this array), I want to make it a clone of one of the existing Ship objects in my prototype array.
1 - How can I run through all the properties in one Ship object and assign them to a second Ship object?
2 - How can I see if a property is an object or a basic type like String or int? Some of the objects in my Ship class need to be cloned, and some are just references that need to stay the same.
One option, arguably the most agile, would be to define clone methods for each class that you need to clone, such as:
class Ship
{
public var prop1:Number;
public var otherClassInstance:OtherClass;
public function clone():Ship
{
var result:Ship = new Ship();
result.prop1 = this.prop1;
result.otherClassInstance = this.otherClassInstance.clone()
}
}
class OtherClass
{
public var prop1:Number;
public function clone():OtherClass
{
var result:OtherClass = new OtherClass();
result.prop1 = this.prop1;
}
}
Another option is to clone an object by using the ByteArray class like this example from the Adobe documentation:
function clone( source:Object ):*
{
var myBA:ByteArray = new ByteArray();
myBA.writeObject( source );
myBA.position = 0;
return( myBA.readObject() );
}
I've seen instances where this approach does not work for cloning instances of custom classes, specifically view classes like Sprites.
Another approach is to use describeType from the flash.utils package. With describeType you can iterate through the properties of an object.
Here is an example of using describeType to inspect the properties of an object that is a part of a utils lib I wrote.
As for checking the type of the property, you can use describeType or you can also use the is operator like this:
if( myObj is SomeClass )
{
}
if( myObj is OtherClass )
{
}
To run through all the properties of one ship object and assign them to a second:
shipobj1:Ship = new Ship();
//set values for all shipobj1 properties
shipobj2:Ship = new Ship();
for (item in shipobj2)
item = shipobj1[item];
Checking if a property value is an object you could use typeof. The limitation of this is that there are only 6 possible types returned: boolean, function, number, object, string, and xml. So for example if you need to know if a property is an array you can't really do that with typeof since that would actually return "object" since "array" isn't one of the 6 options, but if you're just concerned with identifying simple types like numbers and strings versus other stuff it should do the trick:
if(typeof item == "object")
// do whatever with object
else if(typeof item == "string")
// do whatever with string
//etc, etc.
EDIT: Replaced variable "var" with "item" since var is a reserved word.
I am trying to understand the way the AsyncToken works in actionscript. How can I call a remote service and ensure that a specific parameter is available in the result or fault event functions? I think it is the async functionality I want to use.
The following code will hopefully explain what I am trying to do. Feel free to modify the code block as your explanation.
Thanks.
public function testSerivceCall(data:Object, callBackCommand:String):void
{
// Assume callBackCommand == "FOO";
// How can I pass in callBackCommand as a parameter to the result or fault events?
// How do I create an async token here?
var remoteObject:RemoteObject;
remoteObject = new RemoteObject();
remoteObject.destination = "zend";
remoteObject.source = "MyService";
remoteObject.endpoint = "http://example.com/service";
remoteObject.test.addEventListener(ResultEvent.RESULT, _handleTestResult);
remoteObject.test.addEventListener(FaultEvent.FAULT, _handleTestFault);
remoteObject.test(data);
}
private function _handleTestResult( event:ResultEvent ) : void
{
// How do I get the async token value?
// How can I get the value of callBackCommand in this code block?
if (callBackCommand == "FOO")
{
// do something related to "FOO"
}
else
{
// do something else with the result event
}
}
private function _handleTestFault( event:FaultEvent ) : void
{
// How do I get the async token value?
// How can I get the value of callBackCommand in this code block?
}
An edit to make this question more clear:
Assume I make the following method call somewhere in my code:
testSerivceCall(personObject, "LoginCommand");
How do I get access to the actual string "LoginCommand" inside the _handleTestResult function block?
The reason I want to do this is because I want to dynamically call back certain functions and hand off the result data to specific commands that I know ahead of time when I am making the service call.
I am just having a time grokking the AsyncToken syntax and functionality.
I did not even need closures. I added a class as below which I called externally.
The call was like this:
public class MyClass
{
...
var adminServerRO:AdminServerRO = new AdminServerRO();
adminServerRO.testSerivceCall("FOO",cptyId);
}
public class AdminServerRO
{
private function extResult( event:ResultEvent, token:Object ) : void
{
//the token is now accessed from the paremeter
var tmp:String = "in here";
}
private function extFault( event:FaultEvent ) : void
{
var tmp:String = "in here";
}
public function testSerivceCall(callBackCommand:String, cptyId:String):void
{
var remoteObject:RemoteObject = new RemoteObject();
remoteObject.destination = "adminServer";
var token:AsyncToken = remoteObject.getCounterpartyLimitMonitorItemNode(cptyId);
token.addResponder(new AsyncResponder(extResult,extFault,cptyId));
}
}
While the accepted answer will accomplish what the original submitter wants it does not actually answer the question which was asked. An AsyncToken is created as a result of a remote method call and is accessible from the ResultEvent. Since AsyncToken is a dynamic class you can add whatever property to it that you want. The code below should demonstrate this:
public function testSerivceCall(data:Object, callBackCommand:String):void
{
var remoteObject:RemoteObject;
remoteObject = new RemoteObject();
remoteObject.destination = "zend";
remoteObject.source = "MyService";
remoteObject.endpoint = "http://example.com/service";
remoteObject.test.addEventListener(ResultEvent.RESULT, _handleTestResult);
remoteObject.test.addEventListener(FaultEvent.FAULT, _handleTestFault);
var token:AsyncToken = remoteObject.test(data);
token.callBackCommand = callBackCommand;
}
private function _handleTestResult( event:ResultEvent ) : void
{
if (event.token.callBackCommand == "FOO")
{
// do something related to "FOO"
}
else
{
// do something else with the result event
}
}
private function _handleTestFault( event:FaultEvent ) : void
{
//event.token.callBackCommand should be populated here too
}
If you want to access the properties used during the remote call (parameters to the call and/or AsycToken), you can make use of closures. Just define the result event handler inside the calling method as a closure. It can then access any variable in the calling function.
public function testSerivceCall(data:Object, callBackCommand:String):void
{
var _handleTestResult:Function = function( event:ResultEvent ) : void
{
// token is visible here now
if (callBackCommand == "FOO")
{
// do something related to "FOO"
}
else
{
// do something else with the result event
}
}
var remoteObject:RemoteObject;
remoteObject = new RemoteObject();
remoteObject.destination = "zend";
remoteObject.source = "MyService";
remoteObject.endpoint = "http://example.com/service";
remoteObject.test.addEventListener(ResultEvent.RESULT, _handleTestResult);
remoteObject.test.addEventListener(FaultEvent.FAULT, _handleTestFault);
var token = remoteObject.test(data);
}
If I'm reading your question correctly, you're trying to figure out how to access the actual data returned by the ResultEvent ?
If so, assuming you've made the call correctly and you've gotten data back in a format you're expecting:
private function _handleTestResult( event:ResultEvent ) : void
{
// you get the result from the result property on the event object
// edit: assuming the class Person exists with a property called name
// which has the value "John"
var person : Person = event.result as Person;
if (person.name == "John")
{
Alert.show("John: " + person.name);
}
else
{
Alert.show("Not John: " + person.name);
}
}
private function _handleTestFault( event:FaultEvent ) : void
{
// Maybe you know the type of the returned fault
var expectedFault : Object = event.fault as MyPredefinedType
if (expectedFault.myPredefinedTypesPredefinedMethod() == "BAR")
{
// something here
}
}
The ResultEvent has a property called result which will hold an instance of the object returned by the result (it might be the output of an XML file if using a web service, or a serialized object if using AMF, for example). This is what you want to access. Similarly, FaultEvent has a fault property that returns the fault information.
Edit: Changed code in _handleTestResult() in response to Gordon Potter's comment.