I'm learning flex/flash and I'm lost on this one. I have used the "data" in a bunch of views and it works fine. For some reason it isn't working here.
I set a field to a string here:
function LoginLoaded (e:Event):void {
trace(e.target.data);
var ServerReturn:String;
ServerReturn = new String(e.target.data);
data.UserCommonReturnData = ServerReturn;
navigator.pushView(CommonPlaces, data);
}
and here in the common places view I try to load it back:
var CommonPlacesData:String = new String();
var CurrentSelect:String = new String();
CommonPlacesData = new String(data.UserCommonReturnData);
This gives the error "Access of undefined property data" I don't get it because calling on something like data.PickUpTime (also a string) works fine in other views.
The data begins in the first view like this:
[Bindable] public var User:ObjectProxy = new ObjectProxy();
User.ID = "2314084";
navigator.pushView(TaxiNowOrLaterView, User);
then in later views I call on it like this: (works fine)
var PickUpString:String = new String(data.ID);
Any help would be great!! Thanks!!!
There are few things about your code. First, you really should make it a habit to name the identifiers as appropriate to the language. Identifiers that start with the capital letter and subsequently use minuscule letters for the rest of the logical part of the word (system alternatively known as PascalCase) is employed to only name classes. The rest of identifiers should use camelCase (similar to PascalCase, but the first letter isn't capitalized)**. This greatly reduces the effort at understanding your code. A seasoned AS3 programmer would interpret your code as follows:
// Static constant (!) ID of the class User is assigned (?) a value of "2314084"
User.ID = "2314084";
// invoke a method pushView of a local variable navigator with arguments
// of which first is the class TaxiNowOrLater, the second is the class User
navigator.pushView(TaxiNowOrLaterView, User);
while, perhaps, you didn't mean it.
new String();
In the context of AS3 makes no sense at all. Strings are never references, are immutable and have literal syntax the majority of programmers agreed upon. The code above is identical to "". In the similar way, new String(anotherString) has exact same effect as anotherString.
Your question: event.target may be many different things, some of them may have property called "data" and some may not. The general approach to this problem is that you need to cast the value of event.currentTarget or event.target to the type you expect to dispatch the event. Suppose you are expecting an event from an instance of a Button class, then:
private function clickHandler(event:MouseEvent):void {
if (Button(event.currentTarget).enabled) // do things
}
This will not protect you from an error, if the same event was dispatched by an object, which is not a button, but will make the error reporting more conscious, because it would tell you what class was it trying to cast to what other class, when it failed.
If your program logic requires that the handler be aware of events it shouldn't handle (why?) you could then write it like this:
private function clickHandler(event:MouseEvent):void {
var button:Button = event.currentTarget as Button;
if (button && button.enabled) // do things
}
event.target vs event.currentTarget - very-very rarely you would need the event.target, most of the time you need the currentTarget. I'm not saying it is wrong, but, it looks like it might be the problem. target is the object that was the first cause of the event. Events may bubble, which means they may travel the display list hierarchy up and down, first from the parent to child, then in reverse direction. In the example below, suppose there was a label on the button, which was clicked once the event was generated - in such case, even if you added a listener to the button, event.target would be the button label, not the button. currentTarget is, on the contrary, the immediate object which dispatched the event into the handler.
Few more things: ObjectProxy is an idiotic class, you probably shouldn't use at any event. It serves no purpose and, perhaps, buggy, but very few cared to discover its bugs so far. In a nutshell, what it does is as follows: it creates an object, which "watches" dynamic creation, assignment and removal of its properties and dispatches events when these events happen. This behavior is prone to a lot of errors and implicit bugs. For example, is foo.bar = "baz"; foo.bar = "baz"; a reassignment of the same property or not? Is foo.bar.baz = "fizzbuzz"; a modification of foo.bar? What if property name is not a sting? And so on.
Why you shouldn't use it: there is always a better way to treat your data. A more transparent, easier to debug, more efficient. This class is a prototype, which had never really worked. Besides having the behavior described above, it is huge in terms of lines of code that were used to write it. Debugging the errors that happen inside of it requires a lot of time and patience, which are certainly not worth it.
If you need an object to represent a user, define a class, with properties you expect the user to have and just use that class - this will make debugging and understanding your code much easier.
[Bindable] metadata is evil. I can't tell you you should avoid it, because it is used too often, but, I will. You should avoid it as much as possible. I didn't yet encounter an instance of when the use of this meta would be justified. Much in the similar spirit as ObjectProxy it is a prototype, something designed for lazy programmers w/o much consideration for either performance or corner cases. This is, again, a source of a lot of implicit bugs, typically difficult to spot due to the code generated around this meta "swallowing" the errors. The alternative to this meta is plain addEventListener(...) code with custom events.
Unfortunately, a lot of tutorial will use this kind of code to have you quickly started with the language + framework...
** there are some exceptions to this rule: constants are all upper-case and namespace names use underscores to separate the logical part of the word, but never use uppercase letters.
Related
public function starttank(event:MouseEvent):void
{
var Tankdrive:TankDrive = new TankDrive();
Tankdrive.tankstart();
}
It's saying that something in that function contains invalid data.
I have no idea what it is, i checked TankDrive and tankstart(); and both are correct, tankstart() is a public function...
I'm stumped...
EDIT: Error:
Error #2136: The SWF file file:///C|/Users/BigRed/Desktop/TankDrive/TankDrive.swf contains invalid data.
at mainmenu/starttank()
That's the error...
And above the starttank() function is still the same...
Ok, I looked over the files.
I'm puzzled by what you are trying to do.
Your Document class is TankDrive, and it creates an instance of mainmenu, which create ANOTHER instance of TankDrive when you click a button. Which is not what I think you want to do, or you think it's allowing you to access your document class. -- it's not. It's attempting to create a whole new instance of your game.
In short, your design is not making sense, and it's also causing a conflict with the document class resulting in that error.
The quick solution is to NOT have your EventListener & handler for the click in the mainmenu class, and then call the tankstart() method of your document class instead of attempting to create a new instance of TankDrive.
First move that listener into the document class and modify like this :
main.enterTank.addEventListener(MouseEvent.CLICK, starttank);
and then move your handler to the TankDrive class and modify as follows :
public function starttank(event:MouseEvent):void
{
tankstart();
}
This is not the only way to do this, and not really the way that I would do it. But I think that discussion is beyond the scope of this question.
If you want you can contact me at prototype.in.training#gmail.com for more details on that.
The problem is that you have an instance name that's also a class name (and the compiler has assumed that you meant to reference the latter). You probably meant to call your TankDrive variable 'tankDrive', so changing your code snippet to the following will probably help:
public function starttank(event:MouseEvent):void
{
var tankdrive:TankDrive = new TankDrive();
tankdrive.tankstart();
}
It's common and recommended to start all public variable names with a lower case letter, private variables with an underscore, and class names with a capital, though this isn't enforced by the language itself, so this kind of thing can happen.
Here are some guides on conventional variable and function naming that can help you keep track of what each of your vars and functions are supposed to do:
http://www.adobe.com/devnet/actionscript/learning/as3-fundamentals/variables.html
http://www.adobe.com/devnet/actionscript/learning/as3-fundamentals/functions.html
Good luck!
I'm an architect from a strong JavaScript background, but I did some .NET and Java in the past.
However, I wanted to put a hand on ActionScript3, which I was promised that is very related to JavaScript.
As a startup project I took on myself to try port to ActionScript3 one of my favorite assertion utils - should.js - that makes your test codes really pleasant to read.
Updated: 2013-02-19
I saw I confuse with my abstract speaking, so I replaced some of the post with the concrete question in mind.
Here's the full picture:
Consider the following JavaScript code:
Object.defineProperty(Object.prototype, 'should'
, { set: function(){}
, get:
function(){
return new Assertion(Object(this).valueOf());
}
, configurable: true
, enumerable : false
}
);
That is part of the implementation of the JavaScript module Should. The other part is a definition of a the class Assertion, that is constructed with a value, and implements a wide and nice set of assertion methods, against that value. Methods like like
var o = Assertion(actualValue)
o.equals(expectedValue1)
o.moreThan(expectedValue2)
o.contains(expectedValue3)
and aliases to keep english grammer
var o = Assertion(actualValue)
o.equal(expectedValue1)
o.contain(expectedValue3)
and aliases for the lazy sharpshooters, like
o.eql(expectedValue)
o.gt(expectedValue) //greater then
o.gte(...) //greater then or equal
//and so on...
and some connectors that just return this, (which is the instance of Assertion constructed with the test value) like
o.be
o.and
What does it give you?
A test code that looks like this:
var person = getPerson();
Should.exist(person); //that's a static call, and that's easy
//but these are a member calls:
person.should.have("name","age","address","friends");
person.name.should.equal("John");
person.age
.should
.be.number()
.and.be.between(20,30);
person.address
.should
.be.string().and
.startWith("\d").and
.endWith(" st.")
//or even
.and.match(/^[0-9]{1,9}\s+[A-Z][a-z0-9 ]* st\.$/);
person.friends
.should
.be.array().and
.be.between(3,5).and
.containOnlyType(String);
Isn't that wonderful? it's plain English!
You could argue about aesthetics of indentation, where to put the and, and if they are at all necessary, but besides that - anybody can read or write it:
Once you took the 'should' attribute that exists on every object but does not spoil map iterations - you can go on chaining whatever you have to claim regarding the value you started from.
It could have more nifty iteration tools, reflection utilities, be augmented with test functions relevant for your object model, and so on and so forth, but lets just get over the first step :)
But for that, you need every object in the system to feature a non-enumerable smart property called should that in it's getter function returns an Assertion object constructed with the this as the tested value.
(you ain't seen nothing yet - wait to see the beautiful rejection messages it gives! Yummie!!
So yea - I would happily sacrifice the option to call an attribute "should"... and will happily give up intelisense as well - at least as long as it's plain English)
So, in comments, bfavaretto gave us the first step - we know how to prevent enumeration of an attribute - great & thanks!!
Now, can we make it a getter-attribute who's function can access the this?
When I'm done I'm going to put it in some public repo licensed under MIT, for all of us to have fun with :)
Help anybody?
You example is actually 90% correct - but define it like actionscript, not like javascript!
You can still define prototypes in AS3 and they will still work just like prototypes in AS2. The only difference in AS3 is the compiler. AVM2 for some reason does not cast prototypes to native classes (although I didn't test custom classes).
The Prototype Trick: Cast the class as an object.
Eg: if you create:
Array.prototype.random = function():void{}
Then create the object:
var myProtoArray:Array = new Array;
2 things will happen:
myProtoArray.random() //ERROR - this will fail, AVM2 did not map the prototype to Array
but
Object(myProtoArray).random() //WORKS
random() was cast to the Object class, then mapped to Array - I have no idea why!
Hope this helps, cheers.
I confess I'm not keenly familiar with how Javascript works, but if I'm understanding defineProperties purpose correctly, it is a runtime dictation of not just what a property should be, but also the associated namespace to which it belongs (or at least what AS3 considers a namespace).
Class properties are either predefined & only modifiable via custom get() set() functions, or dynamic. Once compiled, their namespace cannot be changed (to my knowledge), so any non-private property is implicitly enumerable, and modifiable whether or not you've written getter/setters (ie: foo.a = value). According to Adobe...
Properties that you create are enumerable, but built-in properties are
generally not enumerable.
That said, you can get a complete list of properties from a class by using describeType. Quite an exhaustive amount of info can be gleaned this way, and I suspect should suit your needs if you wanted to port Mozilla's recreated defineProperties example. Below is an example printing out only property values.
function showProps(obj:*):void {
var desc:XML= describeType(obj);
// public vars
for each (var n:XML in desc.variable){
trace(n.#name + ": " + obj[n.#name]);
}
// getters
for each (n in desc.accessor){
try {
trace(n.#name + ": " + obj[n.#name]);
} catch (error:Error) {
trace("Unable to read write-only property.");
}
}
}
I hope this helps, but I'm certain I don't fully understand what you're trying to accomplish. If you could elaborate, that'd be appreciated.
Ok, guys, thanks for all the help, 22+
I'll give a summary for the people that are interested in the original question, and after that - I'll show you the outcome of my efforts.
The challange was made of two parts:
1 - prevent the augmented (=added on runtime) property from being enumerated
To the first part - thanks to #bfavaretto, commented on the question level - Object.setPropertyIsEnumerable - did the trick great.
2 - make the augmented property operate a getter function with access to the this so it can use it on the constructor of the returned value.
About this second part - Basically - I could not find a way to augment (=add) a property getter to a prototype, and have it operate on instances that enjoy it's API through the inheritance tree.
Anyway, within these limits - here's the outcome:
https://github.com/osher/should.as
Not exact porting because of the platform differences,
and I still have some methods to catch up with the original should.js (like the HTTP testing methods)
but close enough.
The main difference is that instead
var o:Object =
{ name : "Radagast"
, color: "Brown"
}
o.should.have.properties("name","color")
.and.have.property("name","Radagast");
o.name.should.not.equal("Palandoo");
o.color.should.equal("Brown");
you have to go
o.should().have.properties("name","color")
and.have.property("name","Radagast");
o.name.should().not.equal("Palandoo");
o.color.should().equal("Brown");
(the brackets - no getter possible - so the should attribute is a method, and you have to invoke it yourself)
Now if you get stuck and need help from the intellisense, you have to do this:
var should:tdd.Should = o.color.should();
should. <ctrl+space>
which kind'a takes the sting out, but for a peek in the intelisense - it helps
Important
One more thing - you have to force the static constructor of Should as soon in execution as you can,
for example, I do it here:
[Suite]
[RunWith("org.flexunit.runners.Suite")]
public class my_awsome_test_suite
{
//forces the static constructor of tdd.Should
import tdd.Should;
private static var s:Should = new Should();
public var c1:testCase1;
public var c2:testCase2;
public var c3:testCase3;
public var c4:testCase4;
}
I'll probably add some propper README.md later, and more awsome member functions to tdd.Should
Have fun
I'm currently trying to find a "definitive" solution (meaning : finding a solution that seems efficient a complying with OOP precepts) to a recurring problem I've been experiencing for some time : the problem of shared data in different parts of my code.
Take note that I'm not using any MVC framework anywhere here. I'm just refering to my data class as a Model and to the display class as a View (because its the proper names and have nothing to do with the MVC pattern, people made views & models way before the MVC pattern was "created").
Here's my problem :
Whenever I make an application that uses some quite expanded data (for example a game), I try to separate logic (movements, collisions, etc...) and display in two classes. But then, I stumble upon the problem : how to "bind" the data stored in my logic class with the corresponding display objects in my view class, without duplicating data, references, or other things between the different classes ?
Lets take a basic example :
I have a MyLogicClass, holding a Vector of "EntityData" objects (each with position, sizes, various states, everything to handle the logic of my items)
And I have a MyViewClass, creating and displaying Sprites for each EntityData that are in the MyLogicClass, and make them move after them being updated in the game loop.
The first thing that would come to my mind would be to store inside each data element its corresponding view, thus allowing me to loop throught my Vector to update the items logic then update the views accordingly. But that forces me to hold a MyLogicClass reference inside the MyViewClass, to be sure that I can target the entities data, forcing me to couple the two classes (things that I would prefer not to do).
On the other hand, there's the solution of each Entity having an ID, both in my data model (MyLogicClass's EntityData objects having an ID parameter) and in my View class (Sprites holding a reference to its original entity data ID). But when I want to target a specific entity that forces me to loop for it in my data model, then loop for it again to find the related Sprite in my View. This solution allows me to have loose coupling between my data and my view, but looping through hundreds of elements twice every frame (can happen !) really sounds not performance optimized for me.
I may be giving the whole problem a lot more importance that it should deserve, but I've been stumbling upon that more than one time, and I'd love to have some other views than mine about that.
Do you guys have any advice / solution for such an issue ?
Are there some other data formats / hierarchy that I may not be aware of for such case ?
What I've done is 'link' them together using events and event listeners. I have my "model parts" throw specific events that the "display parts" catch and render/update.
I've found this does let me structure some of my tests by writing testing code that would listener for certain events and error checks it that way. My code is still separated and testable on it's own: I can test my "model" by triggering and making sure the right events with the right values are being thrown. Like-wise, I can write some testing code to throw preset events that can be caught by the "display" to see if it has any issues.
Then once it is all working, I just reuse those same event listeners and link to 'each other'.
Later my "controller" (user input) would manipulate the "model" parts, which would cause events to be thrown to the "display" thus be rendered/updated.
I don't know if this is "correct" or not in terms of following the mvc pattern nor do I really have any formal knowledge on these sorts of things. I'd be interested in someone else's more knowledgeable opinion as well.
I think maybe you have over thought the problem. I do this sometimes.
Your view class has to have some type of link to the model obviously and an event is a great way to do it. Something bare bones here to give you an idea.
// Model class
package
{
class MyModel extends EventDispatcher
{
// you can make them public but that would
// be against some oop practices. so private it is
private var m_position:Vector2D;
MyModel(){}
// one way of doing getters/getters
// example: theModel.SetPosition(something);
public function GetPosition():Vector2D { return m_position; }
public function SetPosition(value:Vector2D):void
{
m_position = value;
ModelChanged();
}
// the other way
// sample: theModel.position = something;
public function get position():Vector2D {return m_position; }
public function set position(value:Vector2D):void
{
m_position = value;
ModelChanged();
}
private function ModelChanged():void
{
dispatchEvent(new Event(Event.CHANGE));
}
}
}
// now for our view.
package
{
class MyView extends Sprite // or whatever
{
private var model:MyModel;
MyView(model:MyModel)
{
this.model = model;
model.addEventListener(Event.CHANGE, handleModelChanged);
// fire off an event to set the initial position.
handleModelChanged(NULL);
}
private function handleModelChanged(evt:Event):void
{
x = model.position.x;
y = model.position.y;
// etc etc etc.
}
}
}
Anyhow you don't need the setters if your going to have the logic in the model file also obviously if nothing outside of the model needs to change it no reason for setters. But you do need the getters.
This decouples the model from the view and you can write any view any way you want and all you have to provide is a handler for when the model has changed. Just expose whatever data your views will need with getters.
You now only have to loop through the models and if one changes it will fire off an event and the views that are listening in will update.
hope I didn't miss anything and that explains what you were wanting.
Edit: I forgot to add, you don't have to have "ModelChanged()" all over the place if your using something like an update function. Just update and when your finished fire off the event.
Take the following code:
private var m_iQuanitity:int;
public function get quantity():int
{
return m_iQuantity;
}
That seems to make perfect sense. You can see what the quantity is from an outside class without any problems, but you can't really mess with it at all. Now take the following code:
private var m_acUsers:ArrayCollection = new ArrayCollection();
public function get users():ArrayCollection
{
return m_acUsers;
}
In that case you can't really set the variable directly, but you can still do just about everything else under the sun to it without any problems. You can call its AddItem and RemoveItemAt functions, which can do quite a bit to "set" the variable.
Does it still make sense to do this? I know you can create a duplicate ArrayCollection and just pass the duplicate back to avoid allowing it to be set, but doing stuff like that all over the place, purely for defensive programming, can waste a lot of CPU time. So I guess I'm asking if it still makes sense anyway, how so, and if I'm missing the point of using get and set completely? Thanks!
Syntactically there is nothing wrong with what you've got, but the second example does break down the concept of 'get' by making more than a read only property. If you need to adhere to a read only policy, then you've broken that since now you can manipulate the ArrayCollection.
In the end it comes down to what it is you're tying to do. Does it matter for the project that you can change the value? If you're working on a project with more than a few people, this type of coding will require you to either add a comment or have you explain what you're doing. When ever you do something outside of the norm, that can add confusion, so it's always best to simplify and stick to what is expected, avoiding having to explain something.
Also, I can think of a few ways this could cause problems - changing values outside of the function if you pass the returned property off to other classes that don't know where it came from and having internal code in the original class fail.
For a game I'm attempting to develop, I am writing a resource pool class in order to recycle objects without calling the "new" operator. I would like to be able to specify the size of the pool, and I would like it to be strongly typed.
Because of these considerations, I think that a Vector would be my best choice. However, as Vector is a final class, I can't extend it. So, I figured I'd use composition instead of inheritance, in this case.
The problem I'm seeing is this - I want to instantiate the class with two arguments: size and class type, and I'm not sure how to pass a type as an argument.
Here's what I tried:
public final class ObjPool
{
private var objects:Vector.<*>;
public function ObjPool(poolsize:uint, type:Class)
{
objects = new Vector.<type>(poolsize); // line 15
}
}
And here's the error I receive from FlashDevelop when I try to build:
\src\ObjPool.as(15): col: 18 Error: Access of undefined property type.
Does anybody know of a way to do this? It looks like the Flash compiler doesn't like to accept variable names within the Vector bracket notation. (I tried changing constructor parameter "type" to String as a test, with no results; I also tried putting a getQualifiedClassName in there, and that didn't work either. Untyping the objects var was fruitless as well.) Additionally, I'm not even sure if type "Class" is the right way to do this - does anybody know?
Thanks!
Edit: For clarification, I am calling my class like this:
var i:ObjPool = new ObjPool(5000, int);
The intention is to specify a size and a type.
Double Edit: For anyone who stumbles upon this question looking for an answer, please research Generics in the Java programming language. As of the time of this writing, they are not implemented in Actionscript 3. Good luck.
I have been trying to do this for a while now and Dominic Tancredi's post made me think that even if you can't go :
objects = new Vector.<classType>(poolsize);
You could go something like :
public final class ObjPool
{
private var objects:Vector.<*>;
public function ObjPool(poolsize:uint, type:Class)
{
var className : String = getQualifiedClassName(type);
var vectorClass : Class = Class(getDefinitionByName("Vector.<" + className + ">"));
objects = new vectorClass(poolsize);
}
}
I tried it with both int and a custom class and it seems to be working fine. Of course you would have to check if you actually gain any speed from this since objects is a Vector.<*> and flash might be making some implicit type checks that would negate the speed up you get from using a vector.
Hope this helps
This is an interesting question (+1!), mostly because I've never tried it before. It seems like from your example it is not possible, which I do find odd, probably something to do with how the compiler works. I question why you would want to do this though. The performance benefit of a Vector over an Array is mostly the result of it being typed, however you are explicitly declaring its type as undefined, which means you've lost the performance gain. So why not just use an array instead? Just food for though.
EDIT
I can confirm this is not possible, its an open bug. See here: http://bugs.adobe.com/jira/browse/ASC-3748 Sorry for the news!
Tyler.
It is good you trying to stay away from new but:
Everything I have ever read about Vector<> in actionscript says it must be strongly typed. So
this shouldn't work.
Edit: I am saying it can't be done.
Here see if this helps.
Is it possible to define a generic type Vector in Actionsctipt 3?
Shot in the dock, but try this:
var classType:Class = getDefinitionByName(type) as Class;
...
objects = new Vector.<classType>(poolsize); // line 15
drops the mic
I don't really see the point in using a Vector.<*>. Might as well go with Array.
Anyhow, I just came up with this way of dynamically create Vectors:
public function getCopy (ofVector:Object):Object
{
var copy:Object = new ofVector.constructor;
// Do whatever you like with the vector as long as you don't need to know the type
return copy;
}