Adobe's runtIme error documentation doesn't specify error code 2007 yet it gets raised here and there from time to time for different reasons. The commonality among them seems to be when an API is specifically rejecting a parameter due to it being null. This is opposed to trying to access a null reference. My guess is that this is similar to an InvalidArgumentException in Java, but nothing I come across confirms that.
Anyone with knowledge at this depth?
ActionScript Error #2007: Parameter text must be non-null.
You are probably trying to assing a null to the text property of a TextField :
var txtField:TextField = new TextField();
txtField.text = null;
This error is thrown by the set text function of TextField which expects a string.
Related
Is there any difference of use, efficiency or background technique between
var mc:MovieClip = MovieClip(getChildByName("mc"));
and
var mc:MovieClip = getChildByName("mc") as MovieClip;
?
The choice is just matter of convention, preference or are there cases where you can't use one?
This article describes the differences well:
A key difference between casting and the as operator is the behavior
on failure. When a cast fails in ActionScript 2, null is returned.
When a cast fails in ActionScript 3, a TypeError is thrown. With the
as operator in ActionScript 3, whenever a cast fails the default value
for the datatype is returned.
as also allows you to cast to Array, which wasn't possible before since the conversion function Array() took precedence.
EDIT: concerning performance, using as is reported to be faster than the function call style casting in various articles: [1] [2] [3]. The first article cited looks at the performance differences in depth and reports that as is 4x-4.5x faster.
EDIT 2: Not only is as 4x-4.5x faster in the normal best case, but when you wrap the (cast) style conversion in a try-catch block, and an error actually ends up being thrown, it's more like 30x - 230x faster. In AS3, if you think you're going to do something exceptional (in that it could throw an error) then it's clear that you should always look before you leap. Never use try/catch unless forced to by the API, and indeed that means to never (cast) It also is instructive to look at the performance implications of try/catch even when no exception is thrown. There's a performance penalty to setting up a try/catch block even in the happy case that nothing goes wrong.
Since nobody answered the performance aspect directly yet, and it was in your question, as is dramatically more efficient and faster at runtime than (cast) in AS3.
http://jacksondunstan.com/articles/830
Combined with all the other factors I see absolutely no reason to ever use (cast) and feel it should be avoided completely.
Retracted comment below actually reminds me of a good point as well in regards to this. If you (cast) then you're almost assuredly going to find yourself in a situation where you'll have to try/catch
try{
SubType(foo).bar();
}catch(e:TypeError){
// Can't cast to SubType
}
Which is murderously slow. The only way around that is an is check first
if(foo is SubType){
SubType(foo).bar();
}
Which just seems wrong and wasteful.
AS3 Casting one type to another contains the answer that answers this as well: the "as" keyword assigns null when the conversion fails, otherwise it throws a TypeError.
It is best practice to use the as keyword.
as has the advantage of not throwing an RTE (run-time error). For example, say you have a class Dog that cannot be cast into a MovieClip; this code will throw an RTE:
var dog:Dog = new Dog();
var mc:MovieClip = MovieClip(Dog);
TypeError: Error #1034: Type Coercion failed: cannot convert Dog to MovieClip.
In order for you to make this code "safe" you would have to encompass the cast in a try/catch block.
On the other hand, as would be safer because it simply returns null if the conversion fails and then you can check for the errors yourself without using a try/catch block:
var dog:Dog = new Dog();
var mc:MovieClip = Dog as MovieClip;
if (mc)
//conversion succeeded
else
//conversion failed
Prefer the use of a cast to the use of the as operator. Use the as operator only if the coercion might fail and you want the expression to evaluate to null instead of throwing an exception.
Do this:
IUIComponent(child).document
Not this:
(child as IUIComponent).document
Coding Conventions
(cast) and "as" are two completely different things. While 'as' simply tells the compiler to interpret an object as if it were of the given type (which only works on same or subclasses or numeric/string conversions) , the (cast) tries to use a static conversion function of the target class. Which may fail (throwing an error) or return a new instance of the target class (no longer the same object). This explains not only the speed differences but also the behavior on the Error event, as described by Alejandro P.S.
The implications are clear:
'as' is to be used if the class of an object is known to the coder but not to the compiler (because obfuscated by an interface that only names a superclass or '*'). An 'is' check before or a null check after (faster) is recommended if the assumed type (or a type compatible to auto-coercion) cannot be 100% assured.
(cast) is to be used if there has to be an actual conversion of an object into another class (if possible at all).
var mc:MovieClip = MovieClip(getChildByName("mc"));
will DIRECTLY SET IT AS movieclip
var mc:MovieClip = getChildByName("mc") as MovieClip;
will make mc act like a movieclip, if required type are same
Further to launch or not RTE, or return null, there is a significant difference when we manage errors in a swf loaded into a separate application domain.
Using Loader.uncaughtErrorEvents to handle errors of the loaded swf; if we cast like 'event.error as Error', the resulting error will have the original stack trace (the same that had been caught in the swf that caused the error) while if cast that with Error (event.error), the stack trace of the error will be changed by the current stack trace (in which the cast was made).
Sample Code:
if (event && event.error && event.error is Error) {
debug ("Casting with 'as Error'")
debugStackTrace (event.error as Error);
debug ("casting with 'Error (...)'");
debugStackTrace (Error (event.error));
}
Sample output:
Casting with 'as Error'
ReferenceError: Error # 1056
at Player / onEnterFrame ()
casting with 'Error (...)'
Error: ReferenceError: Error # 1056
at package :: HandlerClass / uncaughtErrorHandler ()
at EventInfo / listenerProxy ()
I have a base class called Room and a subclass called Attic, and another called Basement.
I have a controller class that has an attribute called CurrentLocation which is type Room. The idea is I want to be able to put Attic or Basement in that property and get it back, then cast that to whatever type it is.
So if on the controller the content is of type Attic, I'm trying to figure out how to explicitly cast it. I thought I knew but its not working... Here's what I thought it would be, borrowing from Java:
var myAttic:Attic = (Attic) Controller.CurrentLocation;
This gives me a syntax error:
1086: Syntax error: expecting semicolon before instance.
So how do you cast implicitly? Or can you? I could swear I've done this before as as3.
Here are your options for casting in ActionScript 3:
Use as.
var myAttic:Attic = Controller.CurrentLocation as Attic; // Assignment.
(Controller.CurrentLocation as Attic).propertyOrMethod(); // In-line use.
This will assign null to myAttic if the cast fails.
Wrap in Type().
var myAttic:Attic = Attic(Controller.CurrentLocation); // Assignment.
Attic(Controller.CurrentLocation).propertyOrMethod(); // In-line use.
This throws a TypeError if the cast fails.
I have a mediator that I've registered for a navigation page:
facade.registerMediator(new NavPageMediator(viewComponent));
I'm trying to retrieve that mediator on another page like so:
var navPageMediator:NavPageMediator = facade.retrieveMediator(NavPageMediator.NAME) as NavPageMediator;
However, that statement returns null. If I try to cast it using the NavPageMediator(facade.retrieveMediator(NavPageMediator.NAME)) syntax instead, I get a TypeError: Error #1034: Type Coercion failed: cannot convert com.website.mvc.view.page::NavPageMediator#237560a1 to com.website.mvc.view.page.NavPageMediator.`
I can't, for the life of me, understand why NavPageMediator#237560a1 would be unable to convert to NavPageMediator, nor what happened in between registering the mediator and retrieving it that caused this. Especially since trace(new NavPageMediator() as NavPageMediator); returns [object NavPageMediator].
Incidentally, and this may be part of my problem, I don't understand what the #hash at the end of the object is (#237560a1). Is it simply an internal identifier for that class instance?
Edit:
Left a bit of important info: The SWF in which I instantiate and register the mediator is separate from the SWF in which I try to retrieve it.
Figured it out. It turned out to be an ApplicationDomain issue. Assigning both SWFs (the registrant and the retriever) to the same domain solved the issue.
Additionally, I'm pretty sure the #hash at the end of the class name is an internal reference to the ApplicationDomain to which the class belongs. So NavPageMediator#237560a1 was in a different domain than NavPageMediator (why there was no hash on the second one I'm still not sure; that would have made things a bit clearer).
I narrowed the causes of an AS3 compiler error 1119 down to code that looks similar to this:
var test_inst:Number = 2.953;
trace(test_inst);
trace(test_inst.constructor);
I get the error "1119: Access of possibly undefined property constructor through a reference with static type Number."
Now if I omit the variable's type, I don't get that error:
var test_inst = 2.953;
trace(test_inst);
trace(test_inst.constructor);
it produces the expected output:
2.953
[class Number]
So what's the deal? I like explicitly typing variables, so is there any way to solve this error other than not providing the variable's type?
ok, this is a little hard to explain ... first of all, here is how it works:
var test_inst:Number = 2.953;
trace(test_inst);
trace((test_inst as Object).constructor);
to my understanding, this comes from the fact, that the property constructor comes from the ECMAScript-nature of ActionScript 3. It is an ECMAScript property of Object instances and is inherited through prototypes. From the strictly typed world of ActionScript 3 (which also uses a different inheritance mechanism), this property is thus not available.
greetz
back2dos
http://www.kirupa.com/forum/showpost.php?p=1951137&postcount=214
that has all the info you need :)
basically, trace(test_inst["constructor"]) will work.
Object(someobject).constructor will achieve the same thing -- and you don't have to deal with compiler issues.
Object(someinst) === someclass works as well.
dh
Does anyone know the real difference between the two ways of type casting in Flex 3?
var myObject1:MyObject = variable as MyObject;
var myObject2:MyObject = MyObject(variable);
I prefer to use the second method because it will throw an Error when type cast fails, whereas the first method will just return null. But are there any other differences? Perhaps any advantages to using the first method?
The second type of casting has different behaviour for top level(http://livedocs.adobe.com/flex/2/langref/) types, e.g. Array(obj) does not cast in the straightforward way you describe; it creates a new Array if possible from obj, even if obj is an Array.
I'm sure the times this would cause unexpected behaviour would be rare but I always use "as" for this reason. It means if I do
int(str)
I know it's a cast in the "attempt to convert" sense of the word not in the "I promise it is" sense.
ref: got some confirmation on this from http://raghuonflex.wordpress.com/2007/07/27/casting-vs-the-as-operator/
The as method returns null if cast fails.
The () method throws and error if the cast fails.
If the value of variable is not compatible with MyObject, myObject1 will contain null and you will be surprised by a null pointer error (1009 : cannot access a property or method of a null object reference.) somewhere later in the program when you try to access it. Where as if you are casting using the MyObject(variable) syntax, you will get a type coercion error (1034 : Type Coercion failed: cannot convert _ to _) at the same line itself - which is more helpful than getting a 1009 somewhere later and wondering what went wrong.
I think I read somewhere on this site that as is slighty faster than (), but I can't find the question again.
Beside that this question have been asked many times, you will find an more in-depth answer here.
I recently discovered the very useful [] tag when searching on StackOverflow, it allows to only search in questions tagged with the specified tag(s). So you could do a search like [actionscript-3] as vs cast. There are more search tips here: https://stackoverflow.com/search.
And no; the irony in that I can not find the question about performance and write about how to search is not lost on me ;)
I think as returns back the base class and not null when the casting fails and () throws an error.