How to custom CALayer using subclassing

Question

On UIView there are number of CALayers. Each CALayer consists of CAShapeLayers. CAShapeLayers' path property consists of UIBezierPath.

My objective is when i tap on CALayer i want to get points which i used in the drawing of UIBezierPath. For that i thought of subclassing CALayer which has NSMutableArray to store points. I will be saving points when i am drawing in particular CALayer. So whenever i tap on particular CALayer i will get points associated to that. Also i want to give tag to each CALayer. I do not know how to do this.

The second way is to use CALayer's inbuilt property which will give me points captured in CALayer. But i am not aware of this kind of property.

Please share your ideas how to accomplish this task?

Answer 1

You will need to use the UIView that contains the CALayer to handle the touch events, there is no built in Touch events for CALayers. - (CALayer *)hitTest:(CGPoint)thePoint returns the "deepest" CALayer that the point from the touch event is within. So, if you call [self.layer hitTest:point] it will check all your sublayers and return the correct CALayer

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    CGPoint point = [[touches anyObject] locationInView:self];
    CALayerSubclass *taplayer = [self.layer hitTest:point]
    NSArray *points = [taplayer getPoints];
}

There is no way to get out of a CGPath the points you fed into it. The best you can do are these methods about getting info from the path. So, like you said, your best bet is to subclass CALayer and put all the info you need in a data structure to retrieve later.

// .h
@interface CALayerSubclass : CALayer

@property (nonatomic, strong) NSMutableArray *points;

@end

// .m
-(void)drawInContext:(CGContextRef)ctx {
    ...
    [bezierPath addCurveToPoint:controlPoint1:point1 controlPoint2:point2];
    [points addObject:[NSValue valueWithCGPoint:point1]];  
    [points addObject:[NSValue valueWithCGPoint:point2]];  
    ...
}

Just store all the CGPoints (or most other Core Graphics structure) in an NSValue and throw it into an array.