Dynamic Type for UITextView (and ViewController)

ConsentViewController.swift

//
//  ConsentViewController.swift
//  TextResizingQuestion
//
//  Created by William Power.
//

import UIKit

/**
 This code is meant to help the author of:
 https://stackoverflow.com/questions/79164046/how-to-dynamically-adjust-font-size-in-the-uitextview-xcode-16
 */
class ConsentViewController: UIViewController {
    struct ViewConstants {
        static let viewBackgroundColor: UIColor = .systemGray5
        //The below font declarations and the configuration in the below Label
        //and TextView initializers help the UI scale based on the
        //users' preferred font size.
        //
        //To view the scaling behavior in XCode preview, and turn on
        //"Dynamic Type Variants" for the device you've selected.
        //
        //You can also see the scaling behavior by using the simulator
        //and using alt-command-plus or alt-command-minus, which
        //changes the simulator's preferred text size.
        static let scaledRegularFont: UIFont = UIFontMetrics.default.scaledFont(for: UIFont(name: "AvenirNext-Regular", size: UIFont.labelFontSize)!)
        static let scaledMediumFont: UIFont = UIFontMetrics.default.scaledFont(for: UIFont(name: "AvenirNext-Medium", size: UIFont.labelFontSize)!)
        static let scaledHeaderFont: UIFont = UIFontMetrics(forTextStyle: .headline).scaledFont(for: UIFont(name: "AvenirNext-Medium", size: 20.0)!)
        static let paragraphAlignment: NSMutableParagraphStyle = {
            let retVal = NSMutableParagraphStyle()
            retVal.alignment = .justified
            return retVal
        }()
        static let blueColor: UIColor = UIColor.blue
        static let headerBlue: UIColor = UIColor.systemBlue
        static let consentAttributes:[NSAttributedString.Key: Any] = [
            NSAttributedString.Key.font: scaledRegularFont,
            NSAttributedString.Key.foregroundColor: UIColor.black,
            NSAttributedString.Key.paragraphStyle: paragraphAlignment,
         ]
    }
        
    //MARK: - UI DECLARATIONS
    let consentHeader: UILabel = {
        let label = UILabel()
        label.text = "CONSENT REQUIRED"

        //use dynamic type font & set the control to adjust based on preferred text size
        label.font = ViewConstants.scaledHeaderFont
        label.adjustsFontForContentSizeCategory = true
        
        //enable text wrapping so the label doesn't truncate when size is increased
        label.numberOfLines = 0

        label.textAlignment = .center

        label.textColor = .label
        label.backgroundColor = ViewConstants.headerBlue
        label.textColor = .white
        
        label.layer.cornerRadius = 10
        label.layer.masksToBounds = true
        
        return label
    }()
    
    let consentTextView: UITextView = {
        let textView = UITextView()
        
        textView.font = ViewConstants.scaledRegularFont
        textView.adjustsFontForContentSizeCategory = true

        textView.attributedText = {
            let originalString =
            """
            The content of the app is intended for healthcare professionals only. The information contained within the app is not intended for the general public.

            I confirm that I am a professional within the meaning of §2a of Act No. 40/1995 Coll., on advertising regulation, as amended, i.e., a person authorized to prescribe medicinal products or a person authorized to dispense medicinal products.

            I acknowledge that the information contained herein is not intended for the general public, but for healthcare professionals, with all the risks and consequences arising therefrom for the general public.

            After confirmation, you can continue using the app. We appreciate your understanding - enjoy NeoTools!
            """
            let returnString:NSMutableAttributedString = NSMutableAttributedString(string: originalString ,attributes: ViewConstants.consentAttributes)

            let initialRange:NSRange = NSRange(location: 0, length: 68)
            returnString.addAttribute(.font, value: ViewConstants.scaledMediumFont, range: initialRange)
            returnString.addAttribute(.foregroundColor, value: ViewConstants.blueColor, range: initialRange)
            
            let finalRange:NSRange = NSRange(location: 597, length: 102)
            returnString.addAttribute(.font, value: ViewConstants.scaledMediumFont, range: finalRange)
            returnString.addAttribute(.foregroundColor, value: ViewConstants.blueColor, range: finalRange)
            
            return returnString
        }()
        
        
        textView.isEditable = false
        return textView
    }()
    
    // MARK: - UI label next to toggle, inside box
    let consentToggleContainer: UIView = {
        let view = UIView()
        view.backgroundColor = .systemGray5
        view.layer.cornerRadius = 10
        return view
    }()
    let consentToggleLabel: UILabel = {
        let label = UILabel()
        label.text = "I agree to the above"
        
        label.font = ViewConstants.scaledRegularFont
        label.adjustsFontForContentSizeCategory = true
        label.numberOfLines = 0

        label.textColor = .label
        return label
    }()
    let consentToggle: UISwitch = {
        let switchView = UISwitch()
        switchView.isOn = false
        return switchView
    }()

    // MARK: - UI CONTINUE BUTTON
    let continueButton: UIButton = {
        let button = UIButton()
        button.setTitle("Continue", for: .normal)
        
        if let titleLabel = button.titleLabel {
            titleLabel.font = ViewConstants.scaledHeaderFont
            titleLabel.adjustsFontForContentSizeCategory = true
        }
        
        button.setTitleColor(.label, for: .normal)
        button.backgroundColor = .systemBlue
        button.isEnabled = false
        return button
    }()
    
    // MARK: - UI Configuration
    func addConstraints() {
        let viewsDict = ["header": consentHeader,
                         "text": consentTextView,
                         "toggleContainer": consentToggleContainer,
                         "toggleLabel": consentToggleLabel,
                         "toggle": consentToggle,
                         "button": continueButton]
        
        viewsDict.forEach { _, subview in
            subview.translatesAutoresizingMaskIntoConstraints = false
        }
        
        //constrain subcontainer
        consentToggleContainer.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-[toggleLabel][toggle]-|", metrics: nil, views: viewsDict))
        consentToggleContainer.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-[toggleLabel]-|", metrics: nil, views: viewsDict))
        consentToggleContainer.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-[toggle]-|", metrics: nil, views: viewsDict))

        //constrain top-level views
        view.addConstraints( NSLayoutConstraint.constraints(withVisualFormat: "V:|-[header]-[text]-[toggleContainer]-[button]-|", metrics: nil, views: viewsDict))
        view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-[header]-|", metrics: nil, views: viewsDict))
        view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-[text]-|", metrics: nil, views: viewsDict))
        view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-[toggleContainer]-|", metrics: nil, views: viewsDict))
        view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-[button]-|", metrics: nil, views: viewsDict))
    }
    
    func getScaledLabelFont() -> UIFont {
        guard let customFont = UIFont(name: "AvenirNext-Regular", size: UIFont.labelFontSize) else {
            fatalError("Could not load font")
        }
        return UIFontMetrics.default.scaledFont(for: customFont)
    }
    
    // MARK: - View Lifecycle
    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.addSubview(consentHeader)

        self.view.addSubview(consentTextView)

        self.view.addSubview(consentToggleContainer)

        self.consentToggleContainer.addSubview(consentToggleLabel)

        self.consentToggleContainer.addSubview(consentToggle)
        consentToggle.addTarget(self, action: #selector(switchValueDidChange(sender: )), for: .valueChanged)

        self.view.addSubview(continueButton)

        self.addConstraints()
    }
    
    // MARK: - View Interactions
    @objc func switchValueDidChange(sender: UISwitch) {
        self.continueButton.isEnabled = sender.isOn
    }
}

//enable xcode preview mode
#Preview {
    ConsentViewController()
}

iPhone SE 3rd generation, with x-small user-set preferred text size:

iPhone SE 3rd generation, with AX3 (very large) user-set preferred text size: