Question

I can draw a path and make the view drag-able via gesture recognizer. How would I make a point on the path drag-able. I suppose I would need to identify that point to check it’s location in the view and to reset it’s location to the point to which it is dragged, but that is what I am not sure how to do.

Answer 1

Bro there are function for detecting a hit on CGPath or UIBezierPath. ON touchesBegan: method you can use either one of following methods to detect if the hit point is on the path or not.

For UIBezierPath: - (BOOL)containsPoint:(CGPoint)point

For GGPath :

 bool CGContextPathContainsPoint (
   CGContextRef context,
   CGPoint point,
   CGPathDrawingMode mode
);

Then if this point is on your path then you can set a flag. and In touchesEnd method you can get the translated point. However need to redraw the path. Path will not be elastic.

EDIT: One thing that my work for your case is CAShapeLayer. CAShapeLayer can draw a UIBazierPath or CGPathRef. And also its animatable via its properties of strokeend and strokestart. See following code to get the idea of drawing a path with CAShapeLayer

    UIBezierPath *path = [UIBezierPath bezierPath];
    // Draw your path acording to your requirements
    // Remember that you don't need to stroke path in this implementation
    CAShapeLayer *shapeLayer = [CAShapeLayer layer];
    shapeLayer.path = path.CGPath; // path is a UIBezierPath object
    shapeLayer.strokeColor = [UIColor redColor].CGColor;
    shapeLayer.fillColor = [UIColor clearColor].CGColor;
    shapeLayer.lineWidth = 1.5;
    shapeLayer.strokeStart = 0.0;
    shapeLayer.strokeEnd = 1.0;
    [shapeLayer renderInContext:ctx]; // you can also use addSubLayer: and drawInContext