Example shows how to trigger an impact haptic using UIImpactFeedbackGenerator after a button press.

Swift

class ViewController: UIViewController
{
    lazy var button: UIButton =
    {
        let button = UIButton()
        button.translatesAutoresizingMaskIntoConstraints = false
        self.view.addSubview(button)
        button.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
        button.centerYAnchor.constraint(equalTo: self.view.centerYAnchor).isActive = true
        button.setTitle("Impact", for: .normal)
        button.setTitleColor(UIColor.gray, for: .normal)
        return button
    }()
    
    // Choose between heavy, medium, and light for style
    let impactFeedbackGenerator = UIImpactFeedbackGenerator(style: .heavy)
    
    override func viewDidLoad()
    {
        super.viewDidLoad()
        button.addTarget(self, action: #selector(self.didPressButton(sender:)), for: .touchUpInside)

        // Primes feedback generator for upcoming events and reduces latency
        impactFeedbackGenerator.prepare()
    }
    
    func didPressButton(sender: UIButton)
    {
        // Triggers haptic
        impactFeedbackGenerator.impactOccurred()
    }
}

Objective-C

@interface ViewController ()
@property (nonatomic, strong) UIImpactFeedbackGenerator *impactFeedbackGenerator;
@property (nonatomic, strong) UIButton *button;
@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self.button addTarget:self action:@selector(didPressButton:) forControlEvents:UIControlEventTouchUpInside];
    
    // Choose between heavy, medium, and light for style
    self.impactFeedbackGenerator = [[UIImpactFeedbackGenerator alloc] initWithStyle:UIImpactFeedbackStyleHeavy];
    
    // Primes feedback generator for upcoming events and reduces latency
    [self.impactFeedbackGenerator prepare];
}

- (void)didPressButton:(UIButton *)sender
{
    // Triggers haptic
    [self.impactFeedbackGenerator impactOccurred];
}

#pragma mark - Lazy Init
- (UIButton *)button
{
    if (!_button)
    {
        _button = [[UIButton alloc]init];
        _button.translatesAutoresizingMaskIntoConstraints = NO;
        [self.view addSubview:_button];
        [_button.centerXAnchor constraintEqualToAnchor:self.view.centerXAnchor].active = YES;
        [_button.centerYAnchor constraintEqualToAnchor:self.view.centerYAnchor].active = YES;
        [_button setTitle:@"Impact" forState:UIControlStateNormal];
        [_button setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    }
    return _button;
}

@end