Ios 如何在@AppStorage中存储字体

我想让用户 Select 一种自定义字体.

import SwiftUI

class FontPickerVM: ObservableObject {
    @AppStorage("custom_font") var font: Font? = nil
    // @Published var font: Font? = nil
}

extension Font: RawRepresentable {
    public typealias RawValue = String
    
    
    public init?(rawValue: RawValue) {
        
    }
    
    public var rawValue: RawValue {
        
    }
}

我如何实现Font的RawRepresentable？

我正在使用UIFontPickerViewController Select 一种字体.

import UIKit
import SwiftUI

public struct SUIFontPicker: UIViewControllerRepresentable {
    
    @Environment(\.presentationMode) var presentationMode
    private let onFontPick: (UIFontDescriptor) -> Void
    
    public init(onFontPick: @escaping (UIFontDescriptor) -> Void) {
        self.onFontPick = onFontPick
    }
    
    public func makeUIViewController(context: UIViewControllerRepresentableContext<SUIFontPicker>) -> UIFontPickerViewController {
        let configuration = UIFontPickerViewController.Configuration()
        configuration.includeFaces = true
        configuration.displayUsingSystemFont = false
        
        let vc = UIFontPickerViewController(configuration: configuration)
        vc.delegate = context.coordinator
        return vc
    }
    
    public func makeCoordinator() -> SUIFontPicker.Coordinator {
        return Coordinator(self, onFontPick: self.onFontPick)
    }
    
    public class Coordinator: NSObject, UIFontPickerViewControllerDelegate {
        
        var parent: SUIFontPicker
        private let onFontPick: (UIFontDescriptor) -> Void
        
        
        init(_ parent: SUIFontPicker, onFontPick: @escaping (UIFontDescriptor) -> Void) {
            self.parent = parent
            self.onFontPick = onFontPick
        }
        
        public func fontPickerViewControllerDidPickFont(_ viewController: UIFontPickerViewController) {
            guard let descriptor = viewController.selectedFontDescriptor else { return }
            onFontPick(descriptor)
            parent.presentationMode.wrappedValue.dismiss()
        }
        
        public func fontPickerViewControllerDidCancel(_ viewController: UIFontPickerViewController) {
            parent.presentationMode.wrappedValue.dismiss()
        }
    }
    
    public func updateUIViewController(_ uiViewController: UIFontPickerViewController,
                                       context: UIViewControllerRepresentableContext<SUIFontPicker>) {
        
    }
}

struct FontPicker: View {
    
    @State var isFontPickerPresented = false
    @Environment(\.font) var defaultFont
    
    @StateObject var vm = FontPickerVM()
    
    var body: some View {
        Button {
            isFontPickerPresented = true
            printDetails()
        } label: {
            Text("Select font")
        }
        .sheet(isPresented: $isFontPickerPresented) {
            SUIFontPicker { fontDescriptor in
                let newFont = UIFont(descriptor: fontDescriptor, size: 18)
                vm.font = Font(newFont as CTFont)
                printDetails()
            }
        }
        .font(vm.font)
    }
    
    func printDetails(){
        print("default font:", defaultFont ?? "")
        print("custom font:", vm.font ?? "")
    }
}



struct FontPicker_Previews: PreviewProvider {
    static var previews: some View {
        Form {
            FontPicker()
            FontPicker()
        }
    }
}

我必须指定大小为UIFont(descriptor: fontDescriptor, size: 18)，但我只想更改字体系列.