A UIGestureRecognizer subclass that handles Force Touch events.

CSForceTouchGestureRecognizer.h

//
//  ForceTouchGestureRecognizer.h
//  TouchFlow
//
//  Created by Dana Buehre on 4/26/19.
//  Copyright © 2019 CreatureCoding. All rights reserved.
//

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface CSForceTouchGestureRecognizer : UIGestureRecognizer

@property(nonatomic, readonly, assign) CGFloat force;
@property(nonatomic, assign) CGFloat triggerForce;
@property(nonatomic, assign) BOOL triggerOncePerTouch;

@end

NS_ASSUME_NONNULL_END

CSForceTouchGestureRecognizer.m

//
//  ForceTouchGestureRecognizer.m
//  TouchFlow
//
//  Created by Dana Buehre on 4/26/19.
//  Copyright © 2019 CreatureCoding. All rights reserved.
//

#import "CSForceTouchGestureRecognizer.h"
#import <UIKit/UIGestureRecognizerSubclass.h>
#import <AudioToolbox/AudioToolbox.h>

@implementation CSForceTouchGestureRecognizer {
	CGFloat _maximumForce;
	BOOL _recognized;
}

#pragma mark Initialization

- (instancetype)init {
	if ((self = [super initWithTarget:nil action:nil])) {
		[self _applyDefaults];
	}
	
	return self;
}

- (instancetype)initWithTarget:(id)target action:(SEL)action {
	if ((self = [super initWithTarget:target action:action])) {
		[self _applyDefaults];
	}
	
	return self;
}

#pragma mark UIResponder overrides

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
	[super touchesBegan:touches withEvent:event];
	[self triggerWithState:UIGestureRecognizerStateBegan touches:touches];
}

- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
	[super touchesMoved:touches withEvent:event];
	[self triggerWithState:UIGestureRecognizerStateBegan touches:touches];
}

- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
	[super touchesEnded:touches withEvent:event];
	[self triggerWithState:UIGestureRecognizerStateBegan touches:touches];
}

- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
	[super touchesCancelled:touches withEvent:event];
	[self triggerWithState:UIGestureRecognizerStateBegan touches:touches];
}

#pragma mark UIGestureRecogniser overrides

// prevent blocking other gestures
- (BOOL)canPreventGestureRecognizer:(UIGestureRecognizer *)preventedGestureRecognizer {
	return NO;
}

// reset values when the gesture resets
- (void)reset {
	[super reset];
	_force = 0;
	_recognized = NO;
}

#pragma mark Implementation

// determine the force of this touch and set the gesture state
- (void)triggerWithState:(UIGestureRecognizerState)state touches:(NSSet<UITouch*> *)touches {
	
	if (!touches || !touches.count)
		return;
	
	UITouch *touch = touches.allObjects.firstObject;
	
	// normalize the force to a usable value (0.0 - 1.0)
	_force = touch.force / MIN(touch.maximumPossibleForce, 4.0f);
	
	// set the state as Recognized when the force is greater than the triggerForce and conditions are appropriate
	if (((_triggerOncePerTouch && !_recognized) || (!_triggerOncePerTouch && !_recognized)) && _force >= _triggerForce) {
		
		[self _generateFeedback];
		self.state = UIGestureRecognizerStateRecognized;
	
	} else {
		
		_recognized = NO;
		self.state = state;
	}
}

#pragma mark Internal

// apply default settings
- (void)_applyDefaults {
	[self setCancelsTouchesInView:NO];
	_triggerForce = 0.5f;
	_triggerOncePerTouch = YES;
}

// play feedback
 - (void)_generateFeedback {
	 if (@available(iOS 10.0, *)) {
		UIImpactFeedbackGenerator *generator = [[UIImpactFeedbackGenerator alloc] initWithStyle:UIImpactFeedbackStyleLight];
		[generator prepare];
		[generator impactOccurred];
		generator = nil;
	 } else {
		 AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);
	 }
 }

@end

Usage.md

usage

ForceTouchGestureRecognizer *forceGesture = [[ForceTouchGestureRecognizer alloc] initWithTarget:self action:@selector(handleForceTouchGesture:)];
forceGesture.triggerForce = 0.8f; // <optional> the force at which the gesture is recognized, defaults to 0.5f
forceGesture.triggerOncePerTouch = YES; // <optional> ensure the gesture is not triggered continuously while holding down the touch, defaults to YES
[self addGestureRecognizer:forceGesture];


- (void)handleForceTouchGesture:(ForceTouchGestureRecognizer *)sender {
    if (sender.state == UIGestureRecognizerStateRecognized) {
        NSLog(@"Force Touch Recognized");
    }
}