Practical Dynamic Type, Part 2

Hal9000-Before.swift

import Foundation
import UIKit

// MARK: - Hal9000

class Hal9000: UIView {
    
    /// A `UIFont` that will be used as the typeface of Hal9000's messages
    let staticFont: UIFont = UIFont(name: "GillSans-Light", size: 36.0)!

    /// A `UILabel` that will render Hal9000's messages
    lazy var dialog: UILabel = {
        let label = UILabel()
        /// FontMetrics will make that font scale based on system settings
        label.font = FontMetrics().scaledFont(for: staticFont)
        label.text = "I'm sorry, Dave. I'm afraid I can't do that."
        label.adjustsFontForContentSizeCategory = true
        label.translatesAutoresizingMaskIntoConstraints = false
        label.numberOfLines = 0
        return label
    }()

    override init(frame: CGRect) {
        super.init(frame: frame)
        
        /// Add `dialog` to Hal9000's view
        addSubview(dialog)
        NSLayoutConstraint.activate([
            dialog.topAnchor.constraint(equalTo: safeAreaLayoutGuide.topAnchor),
            dialog.bottomAnchor.constraint(equalTo: safeAreaLayoutGuide.bottomAnchor),
            dialog.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 16),
            dialog.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -16),
            ])
    }
    
    /// Although "required," we don't have to implement init(coder:) for now
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) not implemented for this article.")
    }
}