iOS Core Bluetooth : Getting API MISUSE Warning

Do scan when bluetooth is poweredOn:

func centralManagerDidUpdateState(_ central: CBCentralManager) {
        switch central.state {
        case .unknown:
            print("unknown")
        case .resetting:
            print("resetting")
        case .unsupported:
            print("unsupported")
        case .unauthorized:
            print("unauthorized")
        case .poweredOff:
            print("poweredOff")
            centralManager?.stopScan()
        case .poweredOn:
            print("poweredOn")
            centralManager?.scanForPeripherals(withServices: nil, options: nil)
        }
    }

You have to wait until the [-CBCentralManagerDelegate centralManagerDidUpdateState:] callback has been called. And then, verify that the state is PoweredOn before you start scanning for peripherals.

Please use the following code to solve the warning:

(You can reference to the code in https://github.com/luoxubin/BlueTooth4.0)

if (bluetoothPowerOn) {
    [self.centralManager scanForPeripheralsWithServices:[serviceIDs copy] options:@{CBCentralManagerScanOptionAllowDuplicatesKey:@(NO)}];
}

-(void)centralManagerDidUpdateState:(CBCentralManager *)central{

    switch (central.state) {

        case CBManagerStatePoweredOn:
        {
            bluetoothPowerOn = YES;    //new code
            [self start];
            break;
        }

        default:
        {    
            bluetoothPowerOn = NO;   //new code
            [self stopScan:[NSError hardwareStatusErrorWithMessage:@"Cannot open Bluetooth, please check the setting." hardwareStatus:central.state]];    
            break;
        }
    }
}