我正在尝试复制从22:50开始使用SwiftUI（与使用的UIKit相对应）在WWDC 2019会议“实践结合” https://developer.apple.com/videos/play/wwdc2019/721/中给出的“向导学校注册”示例在会议期间）。
我已经从示例创建了所有发布者：validatedEMail，validatedPassword和validatedCredentials。虽然validatedEMail和validatedPassword可以正常工作，但validatedCredentials使用CombineLatest消耗了两个发布者，却从未触发
//
// RegistrationView.swift
//
// Created by Lars Sonchocky-Helldorf on 04.07.19.
// Copyright © 2019 Lars Sonchocky-Helldorf. All rights reserved.
//
import SwiftUI
import Combine
struct RegistrationView : View {
@ObjectBinding var registrationModel = RegistrationModel()
@State private var showAlert = false
@State private var alertTitle: String = ""
@State private var alertMessage: String = ""
@State private var registrationButtonDisabled = true
@State private var validatedEMail: String = ""
@State private var validatedPassword: String = ""
var body: some View {
Form {
Section {
TextField("Enter your EMail", text: $registrationModel.eMail)
SecureField("Enter a Password", text: $registrationModel.password)
SecureField("Enter the Password again", text: $registrationModel.passwordRepeat)
Button(action: registrationButtonAction) {
Text("Create Account")
}
.disabled($registrationButtonDisabled.value)
.presentation($showAlert) {
Alert(title: Text("\(alertTitle)"), message: Text("\(alertMessage)"))
}
.onReceive(self.registrationModel.validatedCredentials) { newValidatedCredentials in
self.registrationButtonDisabled = (newValidatedCredentials == nil)
}
}
Section {
Text("Validated EMail: \(validatedEMail)")
.onReceive(self.registrationModel.validatedEMail) { newValidatedEMail in
self.validatedEMail = newValidatedEMail != nil ? newValidatedEMail! : "EMail invalid"
}
Text("Validated Password: \(validatedPassword)")
.onReceive(self.registrationModel.validatedPassword) { newValidatedPassword in
self.validatedPassword = newValidatedPassword != nil ? newValidatedPassword! : "Passwords to short or don't matchst"
}
}
}
.navigationBarTitle(Text("Sign Up"))
}
func registrationButtonAction() {
let trimmedEMail: String = self.registrationModel.eMail.trimmingCharacters(in: .whitespaces)
if (trimmedEMail != "" && self.registrationModel.password != "") {
NetworkManager.sharedInstance.registerUser(NetworkManager.RegisterRequest(uid: trimmedEMail, password: self.registrationModel.password)) { (status) in
if status == 200 {
self.showAlert = true
self.alertTitle = NSLocalizedString("Registration successful", comment: "")
self.alertMessage = NSLocalizedString("please verify your email and login", comment: "")
} else if status == 400 {
self.showAlert = true
self.alertTitle = NSLocalizedString("Registration Error", comment: "")
self.alertMessage = NSLocalizedString("already registered", comment: "")
} else {
self.showAlert = true
self.alertTitle = NSLocalizedString("Registration Error", comment: "")
self.alertMessage = NSLocalizedString("network or app error", comment: "")
}
}
} else {
self.showAlert = true
self.alertTitle = NSLocalizedString("Registration Error", comment: "")
self.alertMessage = NSLocalizedString("username / password empty", comment: "")
}
}
}
class RegistrationModel : BindableObject {
@Published var eMail: String = ""
@Published var password: String = ""
@Published var passwordRepeat: String = ""
public var didChange = PassthroughSubject<Void, Never>()
var validatedEMail: AnyPublisher<String?, Never> {
return $eMail
.debounce(for: 0.5, scheduler: RunLoop.main)
.removeDuplicates()
.flatMap { username in
return Future { promise in
self.usernameAvailable(username) { available in
promise(.success(available ? username : nil))
}
}
}
.eraseToAnyPublisher()
}
var validatedPassword: AnyPublisher<String?, Never> {
return Publishers.CombineLatest($password, $passwordRepeat)
.debounce(for: 0.5, scheduler: RunLoop.main)
.map { password, passwordRepeat in
guard password == passwordRepeat, password.count > 5 else { return nil }
return password
}
.eraseToAnyPublisher()
}
var validatedCredentials: AnyPublisher<(String, String)?, Never> {
return Publishers.CombineLatest(validatedEMail, validatedPassword)
.map { validatedEMail, validatedPassword in
guard let eMail = validatedEMail, let password = validatedPassword else { return nil }
return (eMail, password)
}
.eraseToAnyPublisher()
}
func usernameAvailable(_ username: String, completion: (Bool) -> Void) {
let isValidEMailAddress: Bool = NSPredicate(format:"SELF MATCHES %@", "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}").evaluate(with: username)
completion(isValidEMailAddress)
}
}
#if DEBUG
struct RegistrationView_Previews : PreviewProvider {
static var previews: some View {
RegistrationView()
}
}
#endif
我希望提供有效的用户名（有效的电子邮件地址）和两个正确长度的匹配密码时，启用表单按钮。这两个任务负责这两个发布者的工作，我可以在用户界面的两个文本中看到validatedEMail和validatedPassword，我添加了这两个文本是出于调试目的。
第三个发布者（也与上面32:20的视频中显示的代码进行比较）永远不会触发。我确实在这些发布者的validatedPassword Publisher中设置了断点：
guard password == passwordRepeat, password.count > 5 else { return nil }
在此停下来就好了，但是在validatedCredentials Publisher中的第一个断点处有一个类似的断点：
guard let eMail = validatedEMail, let password = validatedPassword else { return nil }
从未到达。
我做错了什么？
答案 0 :(得分：1)
我在这里回答了这个问题：https://forums.swift.org/t/crash-in-swiftui-app-using-combine-was-using-published-in-conjunction-with-state-in-swiftui/26628/9由非常友好和乐于助人的 Nanu Jogi 进行，他没有使用stackoverflow。
这很简单：
添加此行：
.receive(on: RunLoop.main) // run on main thread
validatedCredentials中看起来像这样：
var validatedCredentials: AnyPublisher<(String, String)?, Never> {
return Publishers.CombineLatest(validatedEMail, validatedPassword)
.receive(on: RunLoop.main) // <<—— run on main thread
.map { validatedEMail, validatedPassword in
print("validatedEMail: \(validatedEMail ?? "not set"), validatedPassword: \(validatedPassword ?? "not set")")
guard let eMail = validatedEMail, let password = validatedPassword else { return nil }
return (eMail, password)
}
.eraseToAnyPublisher()
这就是所需要的。
这里又是整个代码的参考时间（已针对Xcode 11.0 beta 5（11M382q）更新）：
//
// RegistrationView.swift
// Combine-Beta-Feedback
//
// Created by Lars Sonchocky-Helldorf on 09.07.19.
// Copyright © 2019 Lars Sonchocky-Helldorf. All rights reserved.
//
import SwiftUI
import Combine
struct RegistrationView : View {
@ObservedObject var registrationModel = RegistrationModel()
@State private var registrationButtonDisabled = true
@State private var validatedEMail: String = ""
@State private var validatedPassword: String = ""
var body: some View {
Form {
Section {
TextField("Enter your EMail", text: $registrationModel.eMail)
SecureField("Enter a Password", text: $registrationModel.password)
SecureField("Enter the Password again", text: $registrationModel.passwordRepeat)
Button(action: registrationButtonAction) {
Text("Create Account")
}
.disabled($registrationButtonDisabled.wrappedValue)
.onReceive(self.registrationModel.validatedCredentials) { newValidatedCredentials in
self.registrationButtonDisabled = (newValidatedCredentials == nil)
}
}
Section {
Text("Validated EMail: \(validatedEMail)")
.onReceive(self.registrationModel.validatedEMail) { newValidatedEMail in
self.validatedEMail = newValidatedEMail != nil ? newValidatedEMail! : "EMail invalid"
}
Text("Validated Password: \(validatedPassword)")
.onReceive(self.registrationModel.validatedPassword) { newValidatedPassword in
self.validatedPassword = newValidatedPassword != nil ? newValidatedPassword! : "Passwords to short or don't match"
}
}
}
.navigationBarTitle(Text("Sign Up"))
}
func registrationButtonAction() {
}
}
class RegistrationModel : ObservableObject {
@Published var eMail: String = ""
@Published var password: String = ""
@Published var passwordRepeat: String = ""
var validatedEMail: AnyPublisher<String?, Never> {
return $eMail
.debounce(for: 0.5, scheduler: RunLoop.main)
.removeDuplicates()
.map { username in
return Future { promise in
print("username: \(username)")
self.usernameAvailable(username) { available in
promise(.success(available ? username : nil))
}
}
}
.switchToLatest()
.eraseToAnyPublisher()
}
var validatedPassword: AnyPublisher<String?, Never> {
return Publishers.CombineLatest($password, $passwordRepeat)
.debounce(for: 0.5, scheduler: RunLoop.main)
.map { password, passwordRepeat in
print("password: \(password), passwordRepeat: \(passwordRepeat)")
guard password == passwordRepeat, password.count > 5 else { return nil }
return password
}
.eraseToAnyPublisher()
}
var validatedCredentials: AnyPublisher<(String, String)?, Never> {
return Publishers.CombineLatest(validatedEMail, validatedPassword)
.receive(on: RunLoop.main)
.map { validatedEMail, validatedPassword in
print("validatedEMail: \(validatedEMail ?? "not set"), validatedPassword: \(validatedPassword ?? "not set")")
guard let eMail = validatedEMail, let password = validatedPassword else { return nil }
return (eMail, password)
}
.eraseToAnyPublisher()
}
func usernameAvailable(_ username: String, completion: (Bool) -> Void) {
let isValidEMailAddress: Bool = NSPredicate(format:"SELF MATCHES %@", "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}").evaluate(with: username)
completion(isValidEMailAddress)
}
}
#if DEBUG
struct RegistrationView_Previews : PreviewProvider {
static var previews: some View {
RegistrationView()
}
}
#endif
答案 1 :(得分：0)
您可能需要将这些发布者的某些验证分组为一个使用者。有一个很酷的操场，概述了合并框架，这就是它们执行类似的use case的方式。在示例中，他们正在验证同一订户内的用户名和密码。在将某些内容发布给用户名和密码发布者之前，订阅者不会执行。
如果希望将它们分开，则需要添加更多发布者，这些发布者基本上概述了密码是否有效以及用户名有效的状态。然后让订阅者收听用户名和密码发布者均有效的时间。
答案 2 :(得分：0)
只需替换
.debounce(for: 0.5, scheduler: RunLoop.main)
使用
.throttle(for: 0.5, scheduler: RunLoop.main, latest: true)
由于发布者订阅中没有昂贵的代码，因此基本上不需要延迟处理。用 latest：true 节流关键事件将几乎以相同的方式完成工作。
我不是反应式编程专家，我可以判断是什么原因，因此我可以选择设计。