observableproprerties1.kt

data class Device(
  val name: String
)

interface DeviceScanner {
  /** Emits a Device opon each new discovery event */
  fun devices() : Observable<Device>
}

class BluetoothDeviceScanner(
  private val bluetoothLeScanner: BluetoothLeScanner
) : DeviceScanner {

  override fun devices(): Observable<Device> {
    return Observable
      .create { emitter ->
        val callback = object : ScanCallback(), Cancellable {

          override fun onScanResult(callbackType: Int, result: ScanResult) {
            emitter.onNext(Device(result.device.name))
          }

          override fun cancel() {
            bluetoothLeScanner.stopScan(this)
          }
        }

        bluetoothLeScanner.startScan(callback)
        emitter.setCancellable(callback)
      }
  }
}