Core Motion and the Motion Manager

IniOS 4 and up, accelerometer and gyroscope values are accessed using the Core Motion framework. This framework provides, among other things, the CMMotionManager class, which acts as a gateway for all the values describing how the device is being moved by its user. Your application creates an instance of CMMotionManager, and then puts it to use in one of two modes:

• It can execute some code for you whenever motion occurs.
• It can hang on to a perpetually updated structure that lets you access the latest values at any time.

The latter method is ideal for games and other highly interactive applications that need to be able to poll the device’s current state during each pass through the game loop. We’ll show you how to implement both approaches.