Fábio,
The reason you are seeing null is because your getInstance() does not assign
the instance of SecondClass to _instance if it hasn't already been
instantiated:
public static function getInstance():SecondClass {
return _instance; //_instance has never been assigned
anything
}
vs.
public static function getInstance():SecondClass {
if (_instance == null)
_instance = new SecondClass();
return _instance;
}
~Ricky
http://codingjourney.blogspot.com
On Fri, Nov 21, 2008 at 12:49 PM, Fabio Pinatti <[EMAIL PROTECTED]> wrote:
> Sure thing!
>
> In my main document class, I have
>
> class BaseClass {
>
> public function BaseClass() {
>
> }
>
> }
>
>
> I have a second document class, that is loaded inside the first one.
>
> class SecondClass {
>
> public static var _instance:SecondClass;
>
> public function SecondClass() {
> _instance = this;
> }
>
> public static function getInstance():SecondClass {
> return _instance;
> }
>
>
> }
>
> and my third document class, that is a movie loaded inside that same
> document as above.
>
> class ThirdClass {
>
> public function ThirdClass() {
> trace (SecondClass.getInstance());
> }
>
>
> }
>
> In Gaia, these 3 classes are respectively Main.as, Nav.as and HomePage.as.
> In that sample I wrote, the output is null. If I declare in my base class,
> something like private var _it:SecondClass, even I didn't init that var,
> and
> compile the app again, magically, it outputs rightly my class instance. The
> weird thing is, for example, If I try the same getInstance() from
> BaseClass,
> for example, it returns correctly too. Im wondering why some classes you
> can
> get instance, and for other, you must declare a var, like my workaround...
>
> Thats weird, no??
>
> Thanks,
>
> Pinatti
>
> On Fri, Nov 21, 2008 at 12:39 PM, Hans Wichman <
> [EMAIL PROTECTED]> wrote:
>
> > Hi Fabio,
> >
> > could you maybe post 2 examples, one that works, and one that doesn't?
> > A picture says more than a thousand words:)
> >
> > greetz
> > JC
> >
> > On Fri, Nov 21, 2008 at 2:19 PM, Fabio Pinatti <[EMAIL PROTECTED]>
> wrote:
> > > Hello,
> > >
> > > About the syntax, I meant the second one, actually, declare the
> _instance
> > > just in constructor, but I just noticed a very weird thing...When I get
> > null
> > > as I was referencing, if I just declare in my main class, a var casting
> > the
> > > type of class that was returning null, it'll work. Seems compiler "see"
> > that
> > > the class exists, and so it returns what I expect. It's really weird,
> > since
> > > the singleton pattern is still the same. If i don't declare this dummy
> > var
> > > with the type I want, even I'm sure the instance exists, it returns
> null.
> > I
> > > really don't know why this is happening, but it was the workaround I've
> > > found.
> > >
> > > About the singleton implementation, I agree with you isn't the best
> thing
> > to
> > > do, but in my case, I'm using that for 3 document classes, that for
> sure
> > > I'll use just one single time, so, it's the quickest solution I guess.
> > >
> > > And very nice your approach about minimize Singleton use. I'll take a
> > try,
> > > it can save a lot of time.
> > >
> > > If you got my problem (i know it's a quite mess to explain), would be
> > great
> > > know why this happens. Maybe it's a Gaia thing that I don't know how to
> > use,
> > > but I was wondering if it was being a stupidity of mine with singleton
> > > concept, since I'm a bit new with oop.
> > >
> > > Thanks a lot,
> > > Pinatti
> > >
> > > On Fri, Nov 21, 2008 at 10:53 AM, Hans Wichman <
> > > [EMAIL PROTECTED]> wrote:
> > >
> > >> Hi,
> > >>
> > >> im not sure about your syntax.
> > >>
> > >> This:
> > >>
> > >> class MyClass {
> > >>
> > >> public static var _instance:MyClass = this;
> > >>
> > >>
> > >> }
> > >>
> > >> will not work.
> > >>
> > >> You are looking for something like:
> > >>
> > >> class MyClass {
> > >>
> > >> public static var _instance:MyClass = null;
> > >>
> > >> public function MyClass () {
> > >> _instance = this;
> > >> }
> > >> }
> > >>
> > >> Although I have to add this is the most rudimentary and worst
> > >> implementation I can come up with, but it will work.
> > >> It will allow public access to your instance variables and overwrite
> > >> any instance already there when you create a page of the same class as
> > >> well :).
> > >>
> > >> As an another example how cool my application registry that I posted
> > >> about yesterday is :)) (shameless self promotion), imagine doing this
> > >> in each page:
> > >>
> > >> _application.register (this);
> > >>
> > >> and when you need a page you do:
> > >>
> > >> HomePage(_application.getRegistree(HomePage))
> > >>
> > >> if you need to get all pages you do:
> > >>
> > >> pageArray = _application.getRegistrees (AbstractPage) (or page can't
> > >> recall the gaia page superclass at the moment).
> > >>
> > >> You can make the _application a singleton if you wish Application.etc
> > >> or you can call it PageRegistry or whatever, the idea remains the
> > >> same. This will reduce the amount of singletons by far. It also shows
> > >> how easy it is to integrate this powerfull approach into whatever
> > >> workflow/framework you work with.
> > >>
> > >> regards,
> > >> JC
> > >>
> > >> On Fri, Nov 21, 2008 at 1:06 PM, Fabio Pinatti <[EMAIL PROTECTED]>
> > wrote:
> > >> > Hello list,
> > >> >
> > >> > I've been having a question since a time ago... I'm using a flash
> > >> framework
> > >> > within my websites (Gaia), and between the classes, I use some
> > singleton
> > >> > pattern to communicate between them. This way, theorically, I can
> get
> > any
> > >> > class instance from another, and I don't need to know the path for
> > each
> > >> > instantiated class on stage. To clarify, imagine I have a home and a
> > form
> > >> > page. I could get the reference for home page from form page, just
> > >> setting
> > >> > up a static var:
> > >> >
> > >> > var _home:HomePage = this;
> > >> >
> > >> > and through a singleton, I could get a HomePage._home, from any
> point
> > of
> > >> my
> > >> > application, right?
> > >> >
> > >> > The point is, for some classes, that works and returns the class
> > >> instance.
> > >> > For other, that doesn't works and returns null, even I'm sure the
> > class
> > >> is
> > >> > with the _home var setted up. I posted this question here, because
> I'm
> > >> > wondering if this can be some problem (of mine) with Singleton
> > pattern,
> > >> and
> > >> > not with framework. Why does Singleton sometimes works, and other
> > times,
> > >> > doesn't? Did you have some similiar problem getting classes
> instances,
> > >> like
> > >> > me?
> > >> >
> > >> > Thanks, and sorry if it's a really stupid question.
> > >> >
> > >> > Kind Regards,
> > >> >
> > >> > --
> > >> > Fábio Pinatti
> > >> > :: web.developer
> > >> > :::: www.pinatti.com.br
> > >> > :::::: 19. 9184.3745 / 3342.1130
> > >> > _______________________________________________
> > >> > Flashcoders mailing list
> > >> > Flashcoders@chattyfig.figleaf.com
> > >> > http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
> > >> >
> > >>
> > >> _______________________________________________
> > >> Flashcoders mailing list
> > >> Flashcoders@chattyfig.figleaf.com
> > >> http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
> > >>
> > >
> > >
> > >
> > > --
> > > Fábio Pinatti
> > > :: web.developer
> > > :::: www.pinatti.com.br
> > > :::::: 19. 9184.3745 / 3342.1130
> > > _______________________________________________
> > > Flashcoders mailing list
> > > Flashcoders@chattyfig.figleaf.com
> > > http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
> > >
> >
> > _______________________________________________
> > Flashcoders mailing list
> > Flashcoders@chattyfig.figleaf.com
> > http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
> >
>
>
>
> --
> Fábio Pinatti
> :: web.developer
> :::: www.pinatti.com.br
> :::::: 19. 9184.3745 / 3342.1130
> _______________________________________________
> Flashcoders mailing list
> Flashcoders@chattyfig.figleaf.com
> http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
>
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