How can I tell if CLLocationManager is actively scanning for a beacon?

Question

When you set up an iOS device as a beacon (peripheral role), you can query its state by calling CBPeripheralManager.isAdvertising. I can't find the equivalent to query whether a device is scanning for a beacon (central role) on CLLocationManager. Any ideas?

Update:

Given David's answer, I encapsulated the code setting up the CLBeaconRegion with the specific UUID and added a boolean variable which is changed when calling startMonitoringRegion and stopMonitoringRegion on CLLocationManager.

Answer 1

I do not believe there is any way this is possible. Even though CoreLocation's iBeacon APIs use Bluetooth LE and CoreBluetooth under the hood, Apple appears to have gone to some lengths to hide this implementation. There is no obvious way to see whether a Bluetooth LE scan is going on at a specific point in time.

Generally speaking, a Bluetooth LE scan is always going on when an app is ranging for iBeacons in the foreground. When an app is monitoring for iBeacons (either in the foreground or background) or ranging in the background, indirect evidence suggests that scans for beacons take place every few minutes, with the exact number ranging from 1-15 depending on phone model and state. I know of no way to programmatically detect the exact times when this starts and stops, although it can be inferred by iBeacon monitoring entry/exit times. If you look at the graph below, the blue dots show the inferred scan times for one particular test case. Details of how I inferred this are described in this blog post.