I think your XML is getting autoconverted into untyped ActionScript objects (because you haven't specified format="e4x"). So you're not getting the benefits of strong typing, which are faster access and better compile-time error checking. - Gordon ________________________________
From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of quiet.mountain Sent: Monday, November 12, 2007 7:17 AM To: [email protected] Subject: [flexcoders] Re: Reference variables / pointers / hex heap addresses Exactly as Gordon says. I was not expecting "ac = event.result.products.rug;" to change the value of ac to point to another object. Thanks for clearing pointers up for me. Gordon, you also mention datatype casting: To parse an XML file of "rugs" into an ArrayCollection of "rug" objects, is your suggestion to write an AS3 Rug Class that mirrors XML rug element fields and then cast ac = Rug(event.result).products.rug to end up with an ArrayCollection of Rug Objects? Sounds like a good idea - but I can already access all of the fields of each object without casting. What does casting buy me in this situation? Cheers, Rich --- In [email protected] <mailto:flexcoders%40yahoogroups.com> , "Gordon Smith" <[EMAIL PROTECTED]> wrote: > > His description indicated that he expected a var like ac to behave like > a C reference. But that's not how AS works; a var like ac behaves like a > C pointer. > > - Gordon > > ________________________________ > > From: [email protected] <mailto:flexcoders%40yahoogroups.com> [mailto:[email protected] <mailto:flexcoders%40yahoogroups.com> ] On > Behalf Of Jerome Clarke > Sent: Friday, November 09, 2007 9:34 PM > To: [email protected] <mailto:flexcoders%40yahoogroups.com> > Subject: Re: [flexcoders] Re: Reference variables / pointers / hex heap > addresses > > > > I think what he's asking is why is it when he points to > > ac = new ArrayCollection(); > > say to for example address 1... but then later tells ActionScript > > ac = event.result.products.rug; > > and the address changes to 2 > > I think he was expecting ac to still point to address 1... but with > the value of address 2 ( copied basically ) > > I might be wrong but as far as I know... unlike C/C++... AS3 isn't > fully native like C/C++ so... allocating/deallocating memory is going > to be slower... it's faster for the Flash player to allocate new > memory, change the address to the new memory, dump the old address in > garbage ( for to be garbage collected later ) rather than reallocating > the memory... also AS3 doesn't exactly work like C/C++ anyways just > like some other languages like PHP > > On Nov 9, 2007 10:02 PM, Gordon Smith [EMAIL PROTECTED] > <mailto:gosmith%40adobe.com> > wrote: > > > > > > > > > > > > > > > > Object references in ActionScript are like C pointers, not like C > > references. The statement > > > > > > ac = event.result.products.rug; > > > > changes the pointer ac so that instead of pointing to the > ArrayCollection > > that you new'd, it now points to the rug. > > > > By the way, this makes no sense since ac is typed as an > ArrayCollection, > > while products.rug is presumably NOT an ArrayCollection. The compiler > can't > > report this error because it doesn't know what type event.result is. > If the > > result object has some type, you should cast it: > > > > ac = SomeResultClass(event.result).products.rug > > > > > > > why can I not directly manipulate my original object from within the > > function? > > > > You can access and change the state of that object within the > function.. For > > example, within the function you can do things like > > > > ac.addItem() > > trace(ac.length) > > > > to manipulate your ArrayCollection. But if you want your function to > make > > collectionAC point to a different object, you must write > > > > collectionAC = ... > > > > inside that function. > > > > Does that help? > > > > - Gordon > > > > ________________________________ > > From: [email protected] <mailto:flexcoders%40yahoogroups.com> <mailto:flexcoders%40yahoogroups.com> > [mailto:[email protected] <mailto:flexcoders%40yahoogroups.com> <mailto:flexcoders%40yahoogroups.com> > ] On > > Behalf Of quiet.mountain > > Sent: Friday, November 09, 2007 10:19 AM > > To: [email protected] <mailto:flexcoders%40yahoogroups.com> <mailto:flexcoders%40yahoogroups.com> > > Subject: [flexcoders] Re: Reference variables / pointers / hex heap > > addresses > > > > > > > > > > > > > > > > > > Hi, > > > > Thanks for the reply, and yes I am coming from a c background. > > > > Even though "the address itself is passed by value" (passing a pointer > by > > copy) the result is still a locally scoped function variable that > points to > > the original object (see debug comments below). > > > > "so you cannot change it [the address]" I don't think I want to change > it > > (the value of the class reference variable that points to the original > > object). I want to make changes to the original object itself (which I > now > > have an address for via the pointer passed by copy). > > > > My question is why does the value of this locally scoped function > variable > > automatically change to point to a newly created object of the same > type > > when I attempt to make changes to it (see debug comments below). > > > > Or to put it another way. If my locally scoped function variable is > now > > actually pointing to my original object why can I not directly > manipulate my > > original object from within the function? > > > > Thanks, Rich > > > > > > > > --- In [email protected] <mailto:flexcoders%40yahoogroups.com> > <mailto:flexcoders%40yahoogroups.com> , "Ralf Bokelberg" > ralf.bokelberg@ > > wrote: > > > > > > Hi Rich > > > > > > Are you coming from a c background? > > > Logically a object parameter is passed by reference, which means, > the > > > address is passed to the method instead of a copy of the object's > > > values. > > > Technically the address itself is passed by value though, so you > > > cannot change it. > > > > > > Cheers > > > Ralf. > > > > > > On Nov 9, 2007 1:03 PM, quiet.mountain quiet.mountain@ wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi, > > > > > > > > I've read through all of the posts here on pointers and also this > > > > page - http://www.mischel.com/diary/2006/07/24.htm, <http://www.mischel.com/diary/2006/07/24.htm,> > <http://www.mischel.com/diary/2006/07/24.htm, <http://www.mischel.com/diary/2006/07/24.htm,> > but can someone > > > ! > clear up something that's been bothering me please? > > > > > > > > Can a function change the value of a non-primitive type that's > passed > > > > as a parameter? > > > > > > > > If I pass a reference to an object as a function parameter, the > local > > > > function variable then holds the address of the object on the > heap. > > > > Fine. > > > > > > > > If I then attempt to make changes to this object within the > function, > > > > the address of the local function reference variable changes to > > > > another address on the heap and creates a new object. The original > > > > object is not updated. We end up with two reference variables > > > > pointing to two different objects on the heap. > > > > > > > > I thought the point of "pass by reference" for non-primitives in > AS3 > > > > was to be able to manipulate objects! directly by passing the hex > > > > address of the! object on the heap (as in c++) > > > > > > > > I understand that a solution is to return the local reference to > the > > > > temporary object from the function and assign it to the class > > > > instance variable, so this is more an exercise in understanding > the > > > > essential workings of AS3. > > > > > > > > Here's some code. > > > > > > > > ----- AS3 Code starts ----- > > > > > > > > private var collectionAC:ArrayCollection = new ArrayCollection(); > > > > // Debug: value of collectionAC is @4deb859 > > > > > > > > private function resultHandler(event:ResultEvent, > ac:ArrayCollection) > > > > { > > > > // Debug: value of ac is also @4deb859 > > > > // There are now 2 reference variables pointing to > > > > // one object on the heap > > > > > > > > ac = event.result.prod! ucts.rug; > > > > > > > > > > > > // Debug: value of ac is now @4f839e1 > > > > // ?WHY? does this line create a new object scoped to > > > > // the function and not modify the original object directly? > > > > } > > > > > > > > ------ MXML code starts ---------- > > > > > > > > <mx:HTTPService id="collectionService" > > > > url="data/collection.xml" > > > > result="resultHandler(event, collectionAC);"/> > > > > > > > > ------ Code ends -------- > > > > > > > > Many thanks, Rich > > > > > > > > > > > > > > > > > > > > -- > > > Ralf Bokelberg ralf.bokelberg@ > > > Flex & Flash Consultant based in Cologne/Germany > > > Phone +49 (0) 221 530 15 35 > > > > > > > > > > > >
