CAShapeLayer not visible in XIB swift iOS

Question

I'm building a custom view using an XIB file. However, I am facing a problem where the layers I add to the view (trackLayer) are not shown on the xib (circleLayer is an animation and I don't expect it to render in xib which is not possible to my knowledge). The code of the owner class for the XIB is shown as follows:

@IBDesignable
class SpinningView: UIView {

@IBOutlet var contentView: SpinningView!

//MARK: Properties
let circleLayer = CAShapeLayer()
let trackLayer = CAShapeLayer()

let circularAnimation: CABasicAnimation = {
    let animation = CABasicAnimation()
    animation.fromValue = 0
    animation.toValue = 1
    animation.duration = 2
    animation.fillMode = kCAFillModeForwards
    animation.isRemovedOnCompletion = false
    return animation
}()

//MARK: IB Inspectables
@IBInspectable var strokeColor: UIColor = UIColor.red {
    ...
}

@IBInspectable var trackColor: UIColor = UIColor.lightGray {
    ...
}

@IBInspectable var lineWidth: CGFloat = 5 {
    ...
}

@IBInspectable var fillColor: UIColor = UIColor.clear {
    ...
}

@IBInspectable var isAnimated: Bool = true {
    ...
}

//MARK: Initialization
override init(frame: CGRect) {
    super.init(frame: frame)
    initSubviews()
}

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

    setup()
    initSubviews()
}

//MARK: Private functions
private func setup() {
    setupTrack()
    setupAnimationOnTrack()
}

private func setupTrack(){
    trackLayer.lineWidth = lineWidth
    trackLayer.fillColor = fillColor.cgColor
    trackLayer.strokeColor = trackColor.cgColor
    layer.addSublayer(trackLayer)
}

private func setupAnimationOnTrack(){
    circleLayer.lineWidth = lineWidth
    circleLayer.fillColor = fillColor.cgColor
    circleLayer.strokeColor = strokeColor.cgColor
    circleLayer.lineCap = kCALineCapRound
    layer.addSublayer(circleLayer)
    updateAnimation()
}

private func updateAnimation() {
    if isAnimated {
        circleLayer.add(circularAnimation, forKey: "strokeEnd")
    }
    else {
        circleLayer.removeAnimation(forKey: "strokeEnd")
    }
}

//MARK: Layout contraints
override func layoutSubviews() {
    super.layoutSubviews()

    let center = CGPoint(x: bounds.midX, y: bounds.midY)
    let radius = min(bounds.width / 2, bounds.height / 2) - circleLayer.lineWidth / 2

    let startAngle = -CGFloat.pi / 2
    let endAngle = 3 * CGFloat.pi / 2
    let path = UIBezierPath(arcCenter: .zero, radius: radius, startAngle: startAngle, endAngle: endAngle, clockwise: true)

    trackLayer.position = center
    trackLayer.path = path.cgPath

    circleLayer.position = center
    circleLayer.path = path.cgPath
}

private func initSubviews() {
    let bundle = Bundle(for: SpinningView.self)
    let nib = UINib(nibName: "SpinningView", bundle: bundle)
    nib.instantiate(withOwner: self, options: nil)
    contentView.frame = bounds
    addSubview(contentView)
}
}

When a view is subclassed in the Main.storyboard, I can see the image and the tracklayer as follows IB UIView but when I go over to the XIB, it does not have the trackLayer(circle around the image) XIB Image. While one can argue that it is working and why I am bothering with this, I think it is important that I design the XIB properly since another person might just see it as an view with only an image (no idea of the animating feature)

Answer 1

When you are designing your XIB, it is not an instance of your @IBDesignable SpinningView. You are, effectively, looking at the source of your SpinningView.

So, the code behind it is not running at that point - it only runs when you add an instance of SpinningView to another view.

Take a look at this simple example:

@IBDesignable
class SpinningView: UIView {

    @IBOutlet var contentView: UIView!
    @IBOutlet var theLabel: UILabel!

    //MARK: Initialization
    override init(frame: CGRect) {
        super.init(frame: frame)
        initSubviews()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        initSubviews()
    }

    private func initSubviews() {
        let bundle = Bundle(for: SpinningView.self)
        let nib = UINib(nibName: "SpinningView", bundle: bundle)
        nib.instantiate(withOwner: self, options: nil)
        contentView.frame = bounds
        addSubview(contentView)

        // this will change the label's textColor in Storyboard
        // when a UIView's class is set to SpinningView
        theLabel.textColor = .red
    }

}

When I am designing the XIB, this is what I see:

But when I add a UIView to another view, and assign its class as SpinningView, this is what I see:

The label's text color get's changed to red, because the code is now running.

Another way to think about it... you have trackColor, fillColor, etc vars defined as @IBInspectable. When you're designing your XIB, you don't see those properties in Xcode's Attributes Inspector panel - you only see them when you've selected an instance of SpinningView that has been added elsewhere.

Hope that makes sense.