Type Alias


The type of block callback for handling magnetometer data.


typedef void (^CMMagnetometerHandler)(CMMagnetometerData *magnetometerData, NSError *error);


Blocks of type CMMagnetometerHandler are called when there is magnetometer data to process. You pass the block into the startMagnetometerUpdatesToQueue:withHandler: method as the second argument. Blocks of this type return no value but take two arguments:


An object that encapsulates a CMMagneticField structure with fields holding magnetic-field values for the three axes of movement.


An error object representing an error encountered in providing magnetometer data. If an error occurs, you should stop magnetometer updates and inform the user of the problem. If there is no error, this argument is nil. Core Motion errors are of the CMErrorDomain domain and the CMError type.

See Also

Managing Magnetometer Updates


The interval, in seconds, at which the system delivers magnetometer data to the block handler.

- startMagnetometerUpdatesToQueue:withHandler:

Starts magnetometer updates on an operation queue and with a specified handler.

- startMagnetometerUpdates

Starts magnetometer updates without a block handler.

- stopMagnetometerUpdates

Stops magnetometer updates.


The latest sample of magnetometer data.