As I’ve already mentioned, events mark certain important stages in the overall lifetime of your application. These events can arrive either as messages to the app delegate (if you implement the appropriate methods) or as notifications to any object (if that object registers for those notifications).
In the old days, before iOS 4, this suite of events was pretty simple:
applicationDidFinishLaunching:. Also received after the end of the situation that caused the app delegate to receive
Starting with iOS 4, however, apps operate in a multitasking environment. The Home button doesn’t terminate your app; it suspends it. This means that your app ...