setNeedsDisplay on CAShapeLayer in order to redraw layer

Question

I'm trying to modify a the path of my CAShapeLayer and then redraw it using setNeedsDisplay,

But for some reason it wont redraw. The only way i can make it to be redrawn is calling viewDidLoad which i am sure is not the correct way.

Here is the code for initialisation:

self.shape.lineWidth = 2.0;
[self.shape setFillColor:[[UIColor clearColor] CGColor]];
self.shape.strokeColor = [[UIColor blackColor] CGColor];
[self.shape setPath:[self.shapePath CGPath]];
self.shape.fillRule = kCAFillModeRemoved;
[self.cuttingView.layer addSublayer:self.shape];

And the gesture recogniser for the drag gesture:

- (void)handlePan:(UIPanGestureRecognizer *)gesture
{
    static CGPoint lastLocation;
    CGPoint location = [gesture locationInView:self.cuttingView];

    if (gesture.state == UIGestureRecognizerStateBegan)
    {
        if (![self.shapePath containsPoint:location] ) {
            gesture.enabled = NO;
        } else {
            lastLocation = location;
        }
    }

    if (gesture.state == UIGestureRecognizerStateChanged) {
        CGAffineTransform translation = CGAffineTransformMakeTranslation((location.x - lastLocation.x), (location.y - lastLocation.y));
        self.shapePath.CGPath = CGPathCreateCopyByTransformingPath(self.shapePath.CGPath, &translation);
        [self.shape setNeedsDisplay];
    }
    gesture.enabled = YES;
} 

I am printing the locations, and they do change, but the screen shows nothing.

How could this be fixed?

Thanks!

Answer 1

You are changing self.shapePath.CGPath, but you are not changing the path in the CAShapeLayer.

Instead of [self.shape setNeedsDisplay], do this again:

[self.shape setPath:[self.shapePath CGPath]];

Answer 2

you don't assign the path to the layer. I'd remove the shapePath variable as it has no use (AFAICS)