Re: [Flashcoders] singleton returns null
I thought it was too (didn't check the existence of _instance), but I was
sure the class was initialized and _instance != null, since it's a document
class, and even after I changed the code, it keeps giving me the error, and
the really weird thing is, it works if I declare a dummy variable, with the
type of class that returns null.. In my example, if I put a private var
_it:SecondClass, the _instance that was null, now returns a valid class
instance.. I'm starting thinking about that it can be a framework thing, and
not the singleton syntax, that is really simple..
Thanks for all, anyway!
Pinatti
On Fri, Nov 21, 2008 at 5:21 PM, Ricky Blaha [EMAIL PROTECTED] wrote:
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
Re: [Flashcoders] singleton returns null
Fabio,
It would be better to sort out what is happening. If you can post the
singleton class code that you are using, together with your simple test
case, that would be good. Ricky's advice should be correct.
Paul
- Original Message -
From: Fabio Pinatti [EMAIL PROTECTED]
To: Flash Coders List flashcoders@chattyfig.figleaf.com
Sent: Monday, November 24, 2008 1:05 PM
Subject: Re: [Flashcoders] singleton returns null
I thought it was too (didn't check the existence of _instance), but I was
sure the class was initialized and _instance != null, since it's a document
class, and even after I changed the code, it keeps giving me the error, and
the really weird thing is, it works if I declare a dummy variable, with the
type of class that returns null.. In my example, if I put a private var
_it:SecondClass, the _instance that was null, now returns a valid class
instance.. I'm starting thinking about that it can be a framework thing, and
not the singleton syntax, that is really simple..
Thanks for all, anyway!
Pinatti
On Fri, Nov 21, 2008 at 5:21 PM, Ricky Blaha [EMAIL PROTECTED] wrote:
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
Re: [Flashcoders] singleton returns null
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
___
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[Flashcoders] singleton returns null
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
Re: [Flashcoders] singleton returns null
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
Re: [Flashcoders] singleton returns null
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
___
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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
Re: [Flashcoders] singleton returns null
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,
Re: [Flashcoders] singleton returns null
Hmmm... I'm not sure I can pinpoint exactly where the problem is in your
code. But there is some weirdness there around where and how that _instance
variable of yours is getting instantiated. It seems like there's nothing to
enforce it only gets created once or doesn't get overwritten multiple times
by different SecondClass object.
What I can do is give you some sample code (totally stolen, incidentally
from Advanced ActionScript 3 with Design Patterns by Joey Lott) that works
for me...
package {
public class MySingletonThing {
private static var _instance:MySingletonThing
public function MySingletonThing() {
// Initialize functions can go here...
}
public static function getInstance():MySingletonThing {
if (MySingletonThing ._instance == null) {
MySingletonThing ._instance = new MySingletonThing ();
}
return MySingletonThing ._instance;
}
}
}
...which you can then call from anywhere using code like...
var foo:MySingletonThing = MySingletonThing.getInstance();
...actually, that's a little too oversimplified. I also include a little
SingletonEnforcer class that helps to ensure somebody doesn't incorrectly
call new MySingletonThing() outside of that class...
package {
public class MySingletonThing {
private static var _instance:MySingletonThing
public function MySingletonThing(enforcer:SingletonEnforcer) {
// Initialize functions can go here...
}
public static function getInstance():MySingletonThing {
if (MySingletonThing ._instance == null) {
MySingletonThing ._instance = new MySingletonThing
(enforcer:SingletonEnforcer);
}
return MySingletonThing ._instance;
}
}
}
// Really important! Make sure you include this SingletonEnforcer class in
your MySingletonThing.as file
class SingletonEnforcer{};
Hope this helps...
--T
On Fri, Nov 21, 2008 at 9:49 AM, 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
Re: [Flashcoders] singleton returns null
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
