In CBCentralManager delegate method didDiscoverPeripheral: never called

问题

I initialize the CBCenteralManager in viewdidload on main queue. First time update state method is called and start scanning for bluetooth devices but didDiscoverPeripheral: delegate method never get called.

Code is :

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.CM = [[CBCentralManager alloc]initWithDelegate:self queue:nil];
}

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

    if (central.state == CBCentralManagerStatePoweredOn) {

        [self.CM scanForPeripheralsWithServices:nil options:nil];

    }
}

- (void)centralManager:(CBCentralManager *)central   didDiscoverPeripheral(CBPeripheral*)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI {   
}
-(void)centralManager:(CBCentralManager *)central didRetrievePeripherals:(NSArray *)peripherals{

}
-(void)centralManager:(CBCentralManager *)central didRetrieveConnectedPeripherals:(NSArray *)peripherals{

}
-(void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error{

}
-(void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error{

}
-(void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral{

}

来源：https://stackoverflow.com/questions/22808538/in-cbcentralmanager-delegate-method-diddiscoverperipheral-never-called