view.swift

class MyView: UILabel {
    init() {
        super.init(frame: .zero)
        numberOfLines = 0
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func draw(_ rect: CGRect) {
        // do nothing, we are not a label actually
    }

    override func textRect(forBounds bounds: CGRect, limitedToNumberOfLines numberOfLines: Int) -> CGRect {
        let size = bounds.size
        let resultSize = performLayout(changeFrames: false, width: size.width)
        return CGRect(origin: .zero, size: resultSize)
    }

    override func layoutSubviews() {
        let width = bounds.size.width
        _ = performLayout(changeFrames: true, width: width)
        super.layoutSubviews()
    }

    private func performLayout(changeFrames: Bool, width: CGFloat?) -> CGSize {
        // calculate new size here depends on width
        // change subviews frames if changeFrames == true
    }
}