enum CaseIterable for fonts enum

AppFonts.swift

import Foundation
import UIKit

enum TextType: CaseIterable {
    
    case title
    case subtitle
    case sectionTitle
    case body
    case comment
}

struct EnumMap<Enum: CaseIterable & Hashable, Value> {
    private let values: [Enum : Value]
    
    init(resolver: (Enum) -> Value) {
        var values = [Enum : Value]()
        
        for key in Enum.allCases {
            values[key] = resolver(key)
        }
        
        self.values = values
    }
    
    subscript(key: Enum) -> Value {
        return values[key]!
    }
}

ViewController.Swift

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        let fonts = EnumMap<TextType, UIFont> { type in
            switch type {
            case .title:
                return .preferredFont(forTextStyle: .headline)
            case .subtitle:
                return .preferredFont(forTextStyle: .subheadline)
            case .sectionTitle:
                return .preferredFont(forTextStyle: .title2)
            case .body:
                return .preferredFont(forTextStyle: .body)
            case .comment:
                return .preferredFont(forTextStyle: .footnote)
            }
        }
        
        let titleFont = fonts[.title]
        let subtitleFont = fonts[.subtitle]
    }

}