I agree that singletons can be easily overused but don't think they are redundant. One mans opinion.
Jim -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Scott Hyndman Sent: 23 March 2006 23:05 To: Flashcoders mailing list Subject: RE: [Bulk] [Flashcoders] Extending a singleton Kind of flamebaity, but I'll bite. I read that article, but this is just one man's opinions. I'm not saying he's wrong, but some of his points largely depend on the usage of the singleton itself (specifically #4). #2 kind of sounds like bullshit to me too. Sure, you can split a singleton into two classes, fine, one for creation and one for the class itself. I just don't see the point. Single responsibility deals with required changes. I don't see how the "singleton" aspect of the class would ever require a change (correct me if I'm wrong). In fact, if you look at a lot of windowing toolkits for operating systems, you will see singleton usage scattered throughout. Just a few I can think of offhand in Apple's Cocoa (a beautifully designed framework in my opinion): Color panel Font panel ...in fact, all panels Application User Defaults It seems to me (because I've never run into any problems) that careful use of singletons is an okay thing to do. I agree that alot of people overuse them and try to force everything and anything into a singleton. I don't agree with that. I just think they have a place. Scott -----Original Message----- From: [EMAIL PROTECTED] on behalf of varfoo Sent: Thu 3/23/2006 5:42 PM To: Flashcoders mailing list Cc: Subject: Re: [Bulk] [Flashcoders] Extending a singleton Hey, It's not considered good practice to use singetons. For reasons why, here's a good article: http://blogs.msdn.com/scottdensmore/archive/2004/05/25/140827.aspx I don't think the protected keyword exists in AS2, but if you have AS3, I'd trying using the protected keyword for the singleton's superclass constructor. I'd recommend trying this as an experiment only. -vf ----- Original Message ----- From: "Christophe Herreman" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, March 23, 2006 7:38 AM Subject: [Bulk] [Flashcoders] Extending a singleton > Hi guys, > > I was wondering if anyone of you ever had a situation where it would be > good to extend a singleton. The first question is: Is it good practice or > should it be avoided at all cost? > > Anyway, I have been trying to extend one, but the problem is that instance > variables are not accessible in the class that extends the singleton (and > which is also a singleton). > > So for instance, take a class A that has a "properties" instance variable > that holds key/value pairs. That var is initialized in the constructor. > > A.getInstance() gives me the single instance. > > B extends A, and B.getInstance() gives me the single instance of B. But > since it extends A, A's constructor is called (although it is private, a > camouflaged protected in AS2) and the properties var is instantiated > again. Get the picture? B will have a properties instance var but it will > not be the same as the one in the singleton of A. > > Am I overlooking something very obvious here or is this actually hard to > accomplish? I changed it from inheritance to using A.getInstance() > internally which works; but now I have to add wrapper methods for every > method in A/ /I want to make available. > > thx in advance, > Christophe > _______________________________________________ > [email protected] > To change your subscription options or search the archive: > http://chattyfig.figleaf.com/mailman/listinfo/flashcoders > > Brought to you by Fig Leaf Software > Premier Authorized Adobe Consulting and Training > http://www.figleaf.com > http://training.figleaf.com _______________________________________________ [email protected] To change your subscription options or search the archive: http://chattyfig.figleaf.com/mailman/listinfo/flashcoders Brought to you by Fig Leaf Software Premier Authorized Adobe Consulting and Training http://www.figleaf.com http://training.figleaf.com _______________________________________________ [email protected] To change your subscription options or search the archive: http://chattyfig.figleaf.com/mailman/listinfo/flashcoders Brought to you by Fig Leaf Software Premier Authorized Adobe Consulting and Training http://www.figleaf.com http://training.figleaf.com
