Multiple Drop Shadows on Single View iOS

The key thing that needs to be added is setting the layers' shadowPath. By default, Core Graphics draws a shadow around the layer's visible content, but in your code neither backgroundColor nor bounds are set for the layers, so the layers are actually empty.

Assuming you have a UIView subclass, you can make it work by adding something like this:

override func layoutSubviews() {
    super.layoutSubviews()
    layer.sublayers?.forEach { (sublayer) in
        sublayer.shadowPath = UIBezierPath(rect: bounds).cgPath
    }
}

I tested this approach on a view with multiple shadows and it worked as expected, as soon as the shadowPath is defined for the shadow layers. Different shadow colors and opacities worked as well, but you have to keep in mind that upper layers in the hierarchy will overlap the layers behind them, so if the front layer has a thick shadow, the other shadows can get hidden by it.