With the Objective-C/Swift Singleton model, why do we create a shared instance and not just use class methods?

Question

It seems we always use a sharedInstance class variable to access the Singleton and perform methods on it. But why don't we just make all operations class methods and not have a variable to deal with at all? [SingletonClass uploadFile:(NSFile *)file] instead of [[SingletonClass sharedInstance] uploadFile:(NSFile *)file] (or the Swift equivalent).

What benefits do the variable bring? Or am I just overlooking some very integral concept in Singletons that not having a variable would prevent?

Furthermore, what stops this variable from being deallocated by memory? I know it's only created once, but why doesn't it ever get removed?

How about providing a link to the previously-asked question? — NRitH, Jul 02 '14 at 01:41

score 1 · Accepted Answer · answered Jul 01 '14 at 17:01

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You create a shared instance if you need to be able to store state. If you can get away with just class methods, that is definitely preferable. The less state you have in your app, especially with singletons, the fewer bugs you will create.

answered Jul 01 '14 at 17:01

drewag

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Indeed, if you do not share state, there is no need for even a class function - a simple function (outside of a class) will do. – Grimxn Jul 01 '14 at 17:06
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@Grimxn Class methods normally provide nice separation of concerns and discoverability – drewag Jul 01 '14 at 17:07
And what stops the variable from being deallocated at some point? – Doug Smith Jul 01 '14 at 17:12
@DougSmith, you always have a static variable with a strong reference to it. – drewag Jul 01 '14 at 17:13

With the Objective-C/Swift Singleton model, why do we create a shared instance and not just use class methods?

1 Answers1

Linked