Re: Proper way to create a singleton without @synchronized ?
Re: Proper way to create a singleton without @synchronized ?
- Subject: Re: Proper way to create a singleton without @synchronized ?
- From: Dave DeLong <email@hidden>
- Date: Sat, 16 Apr 2011 23:11:57 -0700
This is a truly strange question. If you interpret a singleton to be "one and only one", then it doesnt make much sense to ask about subclassing it, because that would imply that you could instantiate one of the base type and one of the sub type, thus making it not fit the definition of a singleton.
However, if we put philosophical discussions aside and simply ask for a maximum of one instance per class, then I'd probably do something like this: instead of using a single static variable to hold your singleton, use a mutable dictionary instead. The keys of the dictionary would be the name of the class, and the corresponding values would be e singleton objects. Override +allocWithZone: to either return the appropriate and existing object, or capture the call to super and save it in the dictionary before returning it. Of course, this would preclude any of the subclasses doing [self release] and returning a new object, but that's probably an adequate compromise.
Dave
Sent from my iPad
On Apr 16, 2011, at 10:20 PM, WT <email@hidden> wrote:
> how would you implement a *true* singleton class that supports subclassing?
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