Correct Answer: The Singleton design pattern ensures a class only has one instance, and provides a global point of access to it The class keeps track of its sole instance and ensures that no other instance can be created Singleton classes are appropriate for situations where it makes sense for a single object to provide access to a global resourceSeveral Cocoa framework classes are singletons They includeNSFileManager, NSWorkspace, NSApplication, and, in UIKit,UIApplication A process is limited to one instance of these classes When a client asks the class for an instance, it gets a shared instance, which is lazily created upon the first request
