KBForceTouchGestureRecognizer.h

#import <UIKit/UIKit.h>

@interface KBForceTouchGestureRecognizer : UIGestureRecognizer
@property (nonatomic) NSUInteger  numberOfTouchesRequired;
@property (nonatomic, readonly) CGFloat currentForce;

@end

@interface _UILinearForceLevelClassifier :NSObject
-(double)standardThreshold;
@end

KBForceTouchGestureRecognizer.m

#import "KBForceTouchGestureRecognizer.h"
#import <UIKit/UIGestureRecognizerSubclass.h>

@interface KBForceTouchGestureRecognizer ()

@property (nonatomic, readwrite) CGFloat currentForce;
@end

@implementation KBForceTouchGestureRecognizer{
_UILinearForceLevelClassifier *_forceSpecs;
}

- (id)initWithTarget:(id)target action:(SEL)action {
	if (self = [super initWithTarget:target action:action]) {
		self.numberOfTouchesRequired = 1.0;
		_forceSpecs= [_UILinearForceLevelClassifier new];
	}
	return self;
}

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

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

- (void)touchesEnded:(NSSet*)touches withEvent:(UIEvent *)event {
	[super touchesEnded:touches withEvent:event];
	[super setState:UIGestureRecognizerStateEnded];
}

-(void)handleForceWithTouches:(NSSet<UITouch *> *)touches{
  if(touches.count!=self.numberOfTouchesRequired){
	    [super setState:UIGestureRecognizerStateFailed];
	}
	CGFloat minimumForce = _forceSpecs.standardThreshold;
	UITouch *t=touches.anyObject;
	self.currentForce=t.force;
	if (self.currentForce >= minimumForce) {
		if (super.state==UIGestureRecognizerStateBegan){
		  [super setState:UIGestureRecognizerStateChanged];
		}
    
    if (super.state!=UIGestureRecognizerStateChanged){
      [super setState:UIGestureRecognizerStateBegan];
    }
  }
}
@end

Usage.md

Usage

KBForceTouchGestureRecognizer*forceTouchGesture=[[KBForceTouchGestureRecognizer alloc] initWithTarget:self action:@selector(handleForceTouch:)];
[self  addGestureRecognizer:forceTouchGesture];

- (void)handleForceTouch:(KBForceTouchGestureRecognizer *)sender {
	if (sender.state == UIGestureRecognizerStateBegan) {
  ///recognized- do stuff here
}
  if (sender.state == UIGestureRecognizerStateChanged) {
  ////Is recognized and changing - Do fancier stuff here
  }
}