Comments on: Singleton Classes

By: Matt Galloway

Matt Galloway — Wed, 01 Sep 2010 11:57:21 +0000

@pawi – that code itself shouldn’t leak. Is your property retained or copied? Either way it should still be fine though. You might need to show me more context in order for me to help on this one.

By: Matt Galloway

Matt Galloway — Wed, 01 Sep 2010 11:54:50 +0000

@jadodgers – you’d use the same one for multiple variables, just have an instance variable of the singleton for each variable you want. Does that make sense?

By: Jsdodgers

Jsdodgers — Tue, 31 Aug 2010 19:48:54 +0000

I am new to Singletons, and I do not quite know how they work. Do you have to have a separate Singleton for every variable that you want to store or can you use the same one for multiple variables. If so, how exactly would this work?

By: pawi

pawi — Tue, 31 Aug 2010 11:19:01 +0000

Hi again,

Instead of posting my whole code, I try to explain what causes my leak:

Whenever I get the shared instance as described in your post, I want to set a property through

myManager.someProperty = [NSString stringWithFormat:@"blabla", someStringValue];

Everytime I set a property this way, it causes an NSString-Object leak… My property is synthesized.

Any Idea?

By: pawi

pawi — Fri, 27 Aug 2010 10:43:42 +0000

Ah Nuuu! To early. Still leaking. Can I send you my code? Would really appreciate your help!

By: pawi

pawi — Fri, 27 Aug 2010 09:46:57 +0000

Hi Matt, thanks for your quick reply. Now that I double-check with instruments, the leak is gone I guess I has to clean my targets. (btw: the leak was from my old implementation. However, it passed Apple’s approval process…) Cheerz!

By: Matt Galloway

Matt Galloway — Fri, 27 Aug 2010 09:29:11 +0000

@pawi – You probably have a bug in the code somewhere. The singleton shouldn’t show as being leaked. What is the actual object that is being leaked?

By: pawi

pawi — Fri, 27 Aug 2010 09:24:57 +0000

Thanks for that post. Just one question: Running the code in Instruments still shows a ‘leak’ for that class. Is this correct, resp. is that the one instance that is never released? Or am I having a bug in the code?

By: Bob Chepperson

Bob Chepperson — Fri, 20 Aug 2010 04:04:05 +0000

That makes sense, thanks for the explanation.

By: Matt Galloway

Matt Galloway — Thu, 19 Aug 2010 08:11:30 +0000

@Bob – Short answer, no. The idea of a singleton is to model 1 object which inherently has a lifetime the same length as your application. Just like you have 1 and only 1 instance that conforms to the UIApplicationDelegate protocol. It doesn’t matter that you never release the object, because you’re not ever going to want to do that if the lifetime is the same as your application.

Does that help?