BTWhee.swift

import Cocoa
import CoreBluetooth
import PlaygroundSupport

class BTHelper: NSObject, CBCentralManagerDelegate, CBPeripheralDelegate {
    
    var centralManager: CBCentralManager
    override init() {
        self.centralManager = CBCentralManager(delegate: nil, queue: nil)
        super.init()
        self.centralManager.delegate = self
    }

    // Required. Invoked when the central manager’s state is updated.
    func centralManagerDidUpdateState(_ manager: CBCentralManager) {
        switch manager.state {
        case .poweredOff:
            print("BLE has powered off")
            centralManager.stopScan()
        case .poweredOn:
            print("BLE is now powered on")
            centralManager.scanForPeripherals(withServices: nil, options: nil)
        case .resetting: print("BLE is resetting")
        case .unauthorized: print("Unauthorized BLE state")
        case .unknown: print("Unknown BLE state")
        case .unsupported: print("This platform does not support BLE")
        }
    }
    
    // Invoked when the central manager discovers a peripheral while scanning.
    func centralManager(_ manager: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData advertisement: [String : Any], rssi: NSNumber) {
        if let name = peripheral.name {
            // RSSI is Received Signal Strength Indicator
            print("Found \"\(name)\" peripheral (RSSI: \(rssi))")
        } else {
            print("Found unnamed peripheral (RSSI: \(rssi))")
        }
        print("Advertisement data:", advertisement)
        print("")
    }
}

let bt = BTHelper()
PlaygroundPage.current.needsIndefiniteExecution = true