Bluetooth ON OFF Check

#import "ViewController.h"
#import <CoreBluetooth/CoreBluetooth.h>

@interface ViewController ()<CBCentralManagerDelegate>
@end

@interface ViewController () {
@property (nonatomic) CBCentralManager *bluetoothManager;
@end

@implementation ViewController

- (void)viewDidLoad {
    
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:NO], CBCentralManagerOptionShowPowerAlertKey, nil];
    
    _bluetoothManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil options:options];
    [_bluetoothManager scanForPeripheralsWithServices:nil options:options];
    [super viewDidLoad];
}

- (IBAction)detectBluetoothb {
    [self centralManagerDidUpdateState:self.bluetoothManager];
}

- (void)centralManagerDidUpdateState:(CBCentralManager *)central {
    NSString *stateString = nil;
    switch(_bluetoothManager.state) {
            
        case CBCentralManagerStateResetting: stateString = @"The connection with the system service was momentarily lost, update imminent."; break;
        case CBCentralManagerStateUnsupported: stateString = @"The platform doesn't support Bluetooth Low Energy."; break;
        case CBCentralManagerStateUnauthorized: stateString = @"The app is not authorized to use Bluetooth Low Energy."; break;
        case CBCentralManagerStatePoweredOff: stateString = @"Bluetooth is currently powered off."; break;
        case CBCentralManagerStatePoweredOn: stateString = @"Bluetooth is currently powered on and available to use."; break;
        default: stateString = @"State unknown, update imminent."; break;
    }
    
    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Bluetooth state" message:stateString preferredStyle:UIAlertControllerStyleAlert];
    [alertController addAction:[UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
        
    }]];
    [self presentViewController:alertController animated:YES completion:nil];
}

@end