singleton in objective c

Question

I saw a singleton example on objective-c book. However, I don\'t know if there is difference of meaning of \'singleton\' definition between objective-c and other langs. Can this

Answer 1

If you want a true singleton, i.e. an object that can be instantiated only once, take a look at Apple's documentation: Creating a Singleton Instance.

Basically, the idea is to override a number of methods related to allocating and managing objects: +allocWithZone (which is called by +alloc), -retain, -release, -copyWithZone, etc., so that it becomes quite difficult to create more than one instance of your singleton class. (It's still possible to create a second instance by calling the runtime directly, but this should be enough to get the point across.)

Pretty much every blogger who has ever written about Objective-C in any capacity has offered an opinion on how to implement singletons. Many of those opinions seem pretty good, and most of them are fairly similar. It's clear that Dave DeLong knows what he's talking about, and his piece on singletons is short, sweet, and gets straight to the point.