Why does CABasicAnimation try to initialize another instance of my custom CALayer?

Question

I get this error:

fatal error: use of unimplemented initializer 'init(layer:)' for class 'MyProject.AccordionLayer'

using the following code. In my view controller:

override func viewDidLoad() {
    let view = self.view as! AccordionView!
    view.launchInitializationAnimations()
}

In my view:

required init(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)

    for var i = 0; i < self.accordions.count; ++i {
        var layer = AccordionLayer(accordion: self.accordions[i])
        layer.accordion = self.accordions[i]
        layer.frame = CGRectMake(0, CGFloat(i) * self.getDefaultHeight(), self.frame.width, self.getDefaultHeight())
        self.layer.addSublayer(layer)
        layer.setNeedsDisplay()
        layers.append(layer)
    }
}

func launchInitializationAnimations() {
    for layer in self.layer.sublayers {
        var animation = CABasicAnimation(keyPath: "topX")
        animation.duration = 2.0
        animation.fromValue = CGFloat(0.0)
        animation.toValue = CGFloat(200.0)
        layer.addAnimation(animation, forKey: "animateTopX")
    }
}

And in my subclassed CALayer

var topX : Int
init(accordion: (color: CGColorRef!, header: String, subtitle: String, image: UIImage?)!) {

    // Some initializations
    // ...

    super.init()
}

I also implement needsDisplayForKey, drawInContext.

I have seen 2-3 other questions with the same error message but I can't really figure out how it is related to my specific case on my own.

Why is CABasicAnimation trying to instantiate a new (my custom) CALayer?

Answer 1

I just ran into the same issue, and I got it working after adding the init(layer:) to my custom CALayer:

override init(layer: Any) {
    super.init(layer: layer)
}

I hope it helps whoever get here.

---

EDIT As Ben Morrow comments, in your override you also have to copy across the property values from your custom class. For an example, see his https://stackoverflow.com/a/38468678/341994.

Answer 2

Why is CABasicAnimation trying to instantiate a new (my custom) CALayer?

Because animation involves making a copy of your layer to act as the presentation layer.