如何讀取特徵值？

Question

我目前正在使用CoreBluetooth工作在BLE設備上。我可以通過CBCentralManagerDelegate找到我的設備，並與我的設備連接。

當我想發現一個服務的特徵時，我可以得到正確的uuid，但是特徵值是nil。有任何想法嗎？

func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) { 
    if error != nil { 
     print("ERROR DISCOVERING CHARACTERISTICS: \(error?.localizedDescription)") 
     return 
    } 
    if let characteristics = service.characteristics { 

     for characteristic in characteristics { 
      print("--------------------------------------------") 
      print("Characteristic UUID: \(characteristic.uuid)") 
      print("Characteristic isNotifying: \(characteristic.isNotifying)") 
      print("Characteristic properties: \(characteristic.properties)") 
      print("Characteristic descriptors: \(characteristic.descriptors)") 
      print("Characteristic value: \(characteristic.value)") 
     } 
    } 
} 

------------------------------------------------------------------- 
Characteristic UUID: FA01 
Characteristic isNotifying: false 
Characteristic properties: CBCharacteristicProperties(rawValue: 26) 
Characteristic descriptors: nil 
Characteristic value: nil 

有關屬性的另一個問題，根據Bluetooth SIG

爲什麼nRFConnect顯示了read，write，notify。但它確實獲得了該特徵的正確價值。

Answer 1

讀取特徵值。 swift 4

func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) { 
    for newChar: CBCharacteristic in service.characteristics!{ 

      peripheral.readValue(for: newChar) 
     }