iOS 13 Core 蓝牙保存的外围服务在被发现后显示为零

Question

我在 iOS 13 和 swift 5 上使用 Core Bluetooth 连接到外围设备。我在连接或发现服务和特性方面没有问题。 但是，我似乎无法保存上述服务和特性以备后用。

这是我连接到外围设备并访问其服务的主要 CentralManager 类：

class CentralManager : NSObject{

    private var centralManager : CBCentralManager!
    var peripheralZero : CBPeripheral!
    override init(){
        super.init()

        centralManager = CBCentralManager(delegate: self, queue: nil)
    }

    func startScanning(){
        if centralManager.state == .poweredOn{
            centralManager.scanForPeripherals(withServices: nil, options: nil)
        }
    }

}

// MARK: - CBCentralManager Delegate Methods
extension CentralManager: CBCentralManagerDelegate{
    func centralManagerDidUpdateState(_ central: CBCentralManager) {
        if central.state == .poweredOn{
            print("central powered on")
        }else{
            print("Central does not support bluetooth")
        }
    }
    func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber){
        if(peripheral.identifier == ParticlePeripheral.DeviceUUID! as UUID){
            centralManager.stopScan()
            peripheralZero = peripheral //Here I save the found peripheral
            peripheral.delegate = self
            centralManager.connect(self.peripheralZero, options: nil)
        }
    }
    func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
        print("connection successful")
        peripheralZero.discoverServices(nil)
    }
}

//MARK: - CBPeripheral Delegate Methods
extension CentralManager: CBPeripheralDelegate{
    func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
        if let services = peripheralZero.services { // this executes to nil but if I instead use:
            // if let services = peripheral.services 
            // it works
            for service in services{
                print(service)
                peripheral.discoverCharacteristics(nil, for: service)
            }
        }

    }
}

来自苹果关于外围设备服务属性的文档：

如果您还没有调用discoverServices(_:) 方法来发现外设的服务，或者如果这样做有错误，则该属性的值为nil。

既然我已经调用了discoverServices，难道我不应该能够使用我的peripheralZero 变量来检索它们吗？ 无论我尝试在代码中的何处访问它，该值都是 nil。 我猜我保存外围设备的方式是导致问题的地方，但我真的不知道。 我是 swift 的新手，所以任何帮助将不胜感激！

Answer 1

extension XXTrain: CBCentralManagerDelegate {
  func centralManagerDidUpdateState(_ central: CBCentralManager) {
    let cState = central.state
    
    switch cState {
    case .poweredOn:
      print(">>central.state is .poweredOn")
      centralManager.scanForPeripherals(withServices: services)
    @unknown default: break
    }
  }
  
  
  func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
    discoveredPeripherals[peripheral.identifier] = peripheral
    myPeripheral = peripheral
    centralManager.connect(peripheral)
  }
  
  func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
    print("  -- Connected: \((peripheral.state == .connected) ? "YES" : "NO"), \(String(describing: peripheral.name)), UUID: \(peripheral.identifier)")
    
    peripheral.delegate = self
    peripheral.discoverServices(services)
  }
}


extension XXTrain: CBPeripheralDelegate {
  func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
    guard let services = peripheral.services else { return }
    
    for service in services {
      print("  >> Discover Services Found : \(service.uuid) service")
      peripheral.discoverCharacteristics(nil, for: service)
    }
  }

我发现的是订单/放置

peripheral.delegate = self

重要的是放在didConnect而不是disDiscover和

myPeripheral = peripheral

在didDiscover放置“持有强引用”的didDiscover