Development

iOS Core Bluetooth: Building BLE Apps for iPhone

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Using Core Bluetooth framework for BLE

  
  

    
    
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    2 min read
    
  


  
  







  
  

    
    
      
      
  1. 
        iOS Core Bluetooth Guide
      
    2. 
      
      
  2. 
        CBCentralManager Setup
      
    3. 
      
      
  3. 
        CBPeripheral and Service Discovery
      
    4. 
      
      
  4. 
        Characteristic Properties
      
    5. 
      
      
  5. 
        Background Modes
      
    6. 
      
    

  









  
  

  
  

    
    

      
iOS Core Bluetooth Guide


Core Bluetooth is Apple's BLE framework for iOS, macOS, watchOS, and tvOS. It uses a delegate-based API centered on CBCentralManager (the central role) and CBPeripheralManager (the peripheral role).


CBCentralManager Setup


Always check radio state before scanning:


class BLEManager: NSObject, CBCentralManagerDelegate {
    var centralManager: CBCentralManager!

    override init() {
        super.init()
        centralManager = CBCentralManager(delegate: self,
                                          queue: .global(qos: .userInitiated))
    }

    func centralManagerDidUpdateState(_ central: CBCentralManager) {
        guard central.state == .poweredOn else { return }
        let uuid = CBUUID(string: "6E400001-B5A3-F393-E0A9-E50E24DCCA9E")
        central.scanForPeripherals(withServices: [uuid], options: nil)
    }
}



CBPeripheral and Service Discovery


Discovery is asynchronous and delegate-driven. Chain calls through delegate methods:


func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
    peripheral.delegate = self
    peripheral.discoverServices(nil)
}

func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
    peripheral.services?.forEach { peripheral.discoverCharacteristics(nil, for: $0) }
}

func peripheral(_ peripheral: CBPeripheral,
                didDiscoverCharacteristicsFor service: CBService, error: Error?) {
    service.characteristics?.forEach {
        if $0.properties.contains(.notify) { peripheral.setNotifyValue(true, for: $0) }
    }
}



Use the GATT Profile Browser to resolve UUID values to standard service names during development.


Characteristic Properties






CBCharacteristicProperties
Use Case






.read
Poll sensor value




.writeWithoutResponse
High-rate command stream




.write
Reliable command with ACK




.notify
Server-initiated push, no ACK




.indicate
Reliable server-initiated push






Background Modes


<key>UIBackgroundModes</key>
<array>
    <string>bluetooth-central</string>
    <string>bluetooth-peripheral</string>
</array>







Mode
Background Behavior






bluetooth-central
Scanning, connections, and callbacks continue




bluetooth-peripheral
Advertising continues at reduced rate




Neither
All BLE paused on app backgrounding






State restoration (CBCentralManagerOptionRestoreIdentifierKey) re-launches the app when the system kills it while a connection is active. Bonding is transparent — iOS stores keys in the Keychain automatically. Reconnect known devices with retrievePeripherals(withIdentifiers:) rather than scanning again.


For the Android equivalent, see Android BLE Development.

    

    

    
    

    
    
    
    

    
    

      




  
Frequently Asked Questions


  

    
    

      
      

        
Yes, our guides range from beginner introductions to advanced topics. Each guide indicates its difficulty level and prerequisites so you can find the right starting point.