Use of undeclared identifier implementing UITouch

Question

I am beginner with Objective C and I got an old project and I am trying to fix and reuse it. I have my class UIViewC that implements UITouch. When I compile I got "use of undeclared identifier _tapCount" error and similar on all properties like _locationInWindow etc.

Any idea how to fix it?

Thank you,

@implementation UITouch (TTCategory)


- (id)initInView:(UIView *)view location:(CGPoint)location {
  if (self = [super init]) {
    _tapCount = 1;
    _locationInWindow = location;
    _previousLocationInWindow = location;

    UIView *target = [view.window hitTest:_locationInWindow withEvent:nil];
    _view = [target retain];
    _window = [view.window retain];
    _phase = UITouchPhaseBegan;
    _touchFlags._firstTouchForView = 1;
    _touchFlags._isTap = 1;
    _timestamp = [NSDate timeIntervalSinceReferenceDate];
  }
  return self;
}


- (void)changeToPhase:(UITouchPhase)phase {
  _phase = phase;
  _timestamp = [NSDate timeIntervalSinceReferenceDate];
}


@end