Please note: this article is part of the older "Objective-C era" on Cocoa with Love. I don't keep these articles up-to-date; please be wary of broken code or potentially out-of-date information. Read "A new era for Cocoa with Love" for more. If you require only a single instance of an object in your application, where should it go? How should you control and manage it? Here are some different appr