How to disable fast application switching (multitasking) on iOS 4?

In iOS 4, when a user presses the Home button, the running app will save the current state and go to background. However I'm developing an app and I don't want it to go to the background. I want it to kill itself, just like in iOS 3开发者_开发技巧 and before. How can I do it? Thanks.

See "Opting Out of Background Execution" in the iOS Application Programming Guide:

"...you can explicitly opt out of the background execution model by adding the UIApplicationExitsOnSuspend key to your application’s Info.plist file and setting its value to YES."