Native Source code for CodeSlicing episode on Property Wrappers Part 04: Age Validation with a Property Wrapper

EditingUserWithAgeValidationDemoNative.swift

//
//  EditingUserWithAgeValidationDemoNative.swift
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
//  of the Software, and to permit persons to whom the Software is furnished to do so,
//  subject to the following conditions:
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
//  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
//  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
//  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
//  AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
//  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
//  Created by Adam Fordyce on 04/06/2021.
//  Copyright © 2020 Adam Fordyce. All rights reserved.
//

import SwiftUI

private let defaultUsers: [User] = [
    
    User(name: "Anthony", age: 53),
    User(name: "Emilio", age: 59),
    User(name: "Ally", age: 58),
    User(name: "Molly", age: 53),
    User(name: "Judd", age: 61),
]

private class AppState: ObservableObject {
    @Published var users: [User] =  defaultUsers.sorted(by: {$0.name < $1.name})
}

private struct User: Equatable, Identifiable {
    
    var id = UUID()
    var name: String
    @Clamped(from: 0, to: 100) var age = 0
}

@propertyWrapper
private struct Clamped: Equatable {

    private let from: Int
    private let to: Int
    private var _wrappedValue: Int = 0
    
    init(from: Int = .min, to: Int = .max) {
        self.init(wrappedValue: from, from: from, to: to)
    }

    init(wrappedValue: Int, from: Int = .min, to: Int = .max) {
        self.from = from
        self.to = to
        self._wrappedValue = wrappedValue.clamped(from: from, to: to)
    }

    var wrappedValue: Int {
        get {
            _wrappedValue
        }
        set {
            _wrappedValue = newValue.clamped(from: from, to: to)
        }
    }
}

struct EditingUserWithAgeValidationDemoNative: View {
    
    @StateObject private var appState = AppState()

    @State private var showingEditScreen = false

    var body: some View {
        NavigationView {
            List(0..<appState.users.count) { index in
                NavigationLink(destination: EditUser(user: appState.users[index]) { user in
                    appState.users[index] = user
                }) {
                    let user = appState.users[index]
                    Text("\(user.name): \(user.age)")
                        .font(.title)
                }
            }
            .navigationTitle("Breakfast Rota")
        }
    }
}

private struct EditUser: View {
    
    @Environment(\.presentationMode) var presentationMode
    @State var user: User
    let saveHandler: (User) -> ()
    
    @State private var errorMessage = ""
    
    init(user: User, saveHandler: @escaping (User) -> ()) {
        _user = State(initialValue: user)
        self.saveHandler = saveHandler
    }
    
    private var isValid: Bool {
        errorMessage.isEmpty
    }
    
    var body: some View {
        ZStack {
            VStack(spacing: 50) {
                ZStack {
                    TextField("Name", text: $user.name)
                        .font(.title)
                        .padding(.horizontal, 8)
                        .padding()
                        .clipShape(Capsule())
                        .overlay(Capsule().stroke(Color.white, lineWidth: 2))
                    if !isValid {
                        Text(errorMessage)
                            .font(.subheadline)
                            .foregroundColor(.orange)
                            .offset(y: -50)
                    }
                }
                HStack(spacing: 20) {
                    CounterButton(sfSymbol: "chevron.left.2") {
                        user.age -= 10
                    }
                    CounterButton(sfSymbol: "chevron.left") {
                        user.age -= 1
                    }
                    Text("\(user.age)")
                        .font(.title)
                        .frame(width: 75)
                        .padding()
                        .clipShape(Capsule())
                        .overlay(Capsule().stroke(Color.white, lineWidth: 2))
                    CounterButton(sfSymbol: "chevron.right") {
                        user.age += 1
                    }
                    CounterButton(sfSymbol: "chevron.right.2") {
                        user.age += 10
                    }
                }
                HStack {
                    ActionButton(sfSymbol: "xmark", color: Color.red.opacity(0.5)) {
                        dismiss()
                    }
                    Spacer()
                    ActionButton(sfSymbol: "checkmark", color: Color.green.opacity(0.5)) {
                        saveHandler(user)
                        dismiss()
                    }
                    .disabled(!isValid)
                    .opacity(isValid ? 1 : 0.2)
                }
            }
        }
        .padding(50)
        .demoPageStyling()
        .onChange(of: user) { updatedUser in
            validateUser()
        }
    }
    
    private func validateUser() {
        errorMessage = Validators.validateName(name: user.name)
    }
   
    private func dismiss() {
        presentationMode.wrappedValue.dismiss()
    }
}

private struct CounterButton: View {
    
    let sfSymbol: String
    let handler: () -> ()
    
    var body: some View {
        Button {
            handler()
        } label: {
            addSFSymbol(sfSymbol)
        }
    }
}

private struct ActionButton: View {
    
    let sfSymbol: String
    let color: Color
    let handler: () -> ()
    
    var body: some View {
        Button {
            handler()
        } label: {
            addSFSymbol(sfSymbol)
                .frame(width: 120, height: 75)
                .clipShape(Capsule())
                .background(Capsule().fill(color))
                .overlay(Capsule().stroke(Color.white, lineWidth: 2))
        }
    }
}

private enum Validators {
    static func validateName(name: String) -> String {
        if name.isEmpty {
            return "Cannot be empty"
        } else if name.count < 2 {
            return "Must be more than 1 character"
        } else if name.containsNumbers {
            return "Cannot contain numbers"
        } else {
            return ""
        }
    }
}

// MARK: ----- EXTENSIONS

private extension View {
    
    func addSFSymbol(_ sfSymbol: String) -> some View {
        Image(systemName: sfSymbol)
            .font(.system(size: 35, weight: .light))
    }
    
    func demoPageStyling() -> some View {
        frame(width: .infinity, height: .infinity)
        .foregroundColor(.white)
        .background(Color(white: 0.1))
        .ignoresSafeArea()
    }
}

private extension Int {
    func clamped(from: Int, to: Int) -> Int {
        Swift.max(from, Swift.min(to, self))
    }
}

private extension String {
    
    var containsNumbers: Bool {
        return rangeOfCharacter(from: .decimalDigits) != nil
    }
}


struct EditingUserWithAgeValidationDemoNative_Previews: PreviewProvider {
    struct EditingUserWithAgeValidationDemoNative_Harness: View {

        var body: some View {
            EditingUserWithAgeValidationDemoNative()
                .demoPageStyling()
                .environment(\.colorScheme, .dark)
        }
    }

    static var previews: some View {
        EditingUserWithAgeValidationDemoNative_Harness()
            .previewDevice("iPhone 12 Pro Max")
            .previewDisplayName("iPhone 12 Pro Max")
    }
}