CODEWITHSUNDEEP
iphoneobjective-cdesign-patternsarchitecturesingleton
Rits
Rits

Reputation: 5175

Should this object be a singleton?

A comment at one of my other questions got me thinking. Right now I am using a singleton Session. It's an encapsulation of a constant TCP connection to my server. It should connect on application launch, and stay connected during the whole lifetime of the application. I only need 1 (it makes no sense to have multiple connections to my server from the same app). And it should be globally accessible.

Is it bad design to use a singleton for this kind of object?

Upvotes: 1

Views: 294

Answers (2)

Sam Ritchie
Sam Ritchie

Reputation: 11038

No, the singleton pattern sounds quite good for this application. I have a similar situation in an app of mine, with a class that manages an instance of iAd. I don't want to load ads over and over again, depending on the window; I just want to shuffle it around.

Similarly, you have a session that you want to maintain; the alternative to a singleton is to initialize it in the AppDelegate and access it from around the app. This is functionally equivalent to the singleton pattern, but far clunkier, as you're really just piggybacking on a class you know will stick around.

Upvotes: 2

jer
jer

Reputation: 20236

If there can never be more than 1, and it needs to be globally available, then the singleton pattern does make sense here. However, this information was left out of your previous question, which is why I commented on it the way I did.

Far too many people lean on singletons to solve problems easily rather than finding real solutions to the problem. In this case, I'll draw a parallel with the UIScreen or UIDevice on iOS devices:

UIScreen has a mainScreen singleton, which refers to the screen on your iPhone, iPad, whatever. There can only ever be one main screen on these devices.

Conversely, UIDevice has a currentDevice class method which achieves the same purpose: There can only be one device.

Upvotes: 2

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