The Singleton pattern in Objective-C is a great way of creating a global single-instance of an object, and we do see them in abundance even within Apple's own SDK, as Luke Redpath identifies:
Even accessing AppDelegate, you can access properties:
(anAppDelegate*)[[UIApplication sharedApplication] delegate]
There are a few articles on the web on how to create such global convenience classes, that allow you to reference a single true source of property values, but trying to find one that is ARC-compliant is a bit trickier. Thankfully, Luke Repath has created a macro that would help with this. In fact, it's dead simple, and in three steps.
Step One and Two:
Create a macro, like in your app's .pch file, as follows:
The second snipped shows how you would create that specific class you wish to share across your app.
Powered with your macro, created in the first step, you get predictive text where you refer or link up to your shared class:
That's it, you can access shared properties inside your object throughout your application.