iOS8: How to clear a UIView from a UIViewController - objective-c

Question

I'm trying to update my app to use a storyboard with auto-layout. Using a XIB, I have this working fine. My app has a view controller with a subView defined in Interface Builder. I draw in the subView.
That works.
But I cannot clear (or undo/redo). I can see that the UIView methods are invoked, but I must not be doing something I'm supposed to do.
Here are some code snips, and I'd appreciate some help:
VC simply calls the view:
- (IBAction)eraseButtonTapped:(id)sender {
NSLog(#"%s", __FUNCTION__);
savedImage.image = drawImage.image;
[drawingView eraseButtonClicked];
}
UIView:
- (void)eraseButtonClicked {
NSLog(#"%s", __FUNCTION__);
self.bufferArray = [self.currentArray mutableCopy];
[self.currentArray removeAllObjects];
[self setNeedsDisplay];
}
Both functions log..
These are the touch methods:
#pragma mark - Touch Methods
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"%s", __FUNCTION__);
self.currentColorPath = [[DrawingPath alloc] init];
[self.currentColorPath setColor:self.currentColor];
UITouch *touch= [touches anyObject];
[self.currentColorPath.path moveToPoint:[touch locationInView:self]];
[self.currentArray addObject:self.currentColorPath];
[self.redoStack removeAllObjects];
lastPoint = [touch locationInView:self];
lastPoint.y -= 20;
if ([touch tapCount] == 2) {
[self alertOKCancelAction];
return;
}
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"%s", __FUNCTION__);
UITouch *touch = [touches anyObject];
[self.currentColorPath.path addLineToPoint:[touch locationInView:self]];
[self setNeedsDisplay];
CGPoint currentPoint = [touch locationInView:self];
currentPoint.y -= 20;
lastPoint = currentPoint;
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"%s", __FUNCTION__);
self.currentColorPath = nil;
}
The view calls a separate object to handle the drawing.. This is a code snippet (removing non-relevant bits).
- (id)init {
//NSLog(#"%s", __FUNCTION__);
if (!(self = [super init] ))
return nil;
path = [[UIBezierPath alloc] init];
_path.lineCapStyle=kCGLineCapRound;
_path.lineJoinStyle=kCGLineJoinRound;
[_path setLineWidth:brush];
return self;
}
- (void)draw {
NSLog(#"%s", __FUNCTION__);
[self.color setStroke];
[self.path stroke];
}