Re: Singletons?
Re: Singletons?
- Subject: Re: Singletons?
- From: Charles Jolley <email@hidden>
- Date: Fri, 21 Jun 2002 03:22:32 -0500
I think you mean declaring a static in the .m and providing access to it
through a class accessor method. This is the "Cocoa" way of doing a
singleton. As long as your static variable is not exported through the
header file, someone would have to be very deliberate to change the
contents of your static.
Anyway, you're not much safer any other way since someone could simply
override your class accessor method using a category or a subclass
posing as your class. In fact, if someone had only a binary of your
class and the header file, this latter approach would be easier than
tracking down a static variable.
On the flip side, sometimes you _want_ someone to be able to change the
singleton instance so they can replace your instance with an "upgraded"
version of their own. Cocoa does not have a standard pattern for doing
this. Some classes, such as NSFontManager, allow you to designate a
factory class to create the singleton. Others will use the first
instance of the class or any subclass.
As for the namespace part...well, yeah, that is annoying. Objective-C
as a whole doesn't having the whole namespace management thing down very
well, IMHO. I would really like to have a Java-like packages system
instead of having to use the two letter prefixes.
Cheers,
-C
On Friday, June 21, 2002, at 02:43 AM, The Amazing Llama wrote:
Okay, so ObjC has no static variables.
How do you do a Singleton? What I'm seeing in code on the 'net is to
make a global static variable in the .m, but this seems dangerous
(someone could change it out from under you, and you can't do anything
to stop them) and not at all object oriented (it's just floating out
there, polluting the global namespace).
There has to be a better way... right?
-The Amazing Llama <tallama at mac dot com>
"Life is like an exploded clown. It's really funny until you figure out
what just happened."
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| | >Singletons? (From: The Amazing Llama <email@hidden>) |