xcode - @Published ObservedObjects SwiftUI 更新未发生
问题描述
@Published ObservedObjects SwiftUI 更新未发生
我创建了一个非常基本的 ObservableObject 应用程序,并且一些绑定已正确更新,而有些则没有。我一定错过了一些简单的东西。仅两个视图 - 开始视图和第二个视图。我只使用文本、按钮和切换——只是为了测试这个概念。
我想将启动属性值存储在 UserDefaults 中。那部分似乎工作正常。当我在第二页上进行更改时,它们会在该页面上更新,并且 UserDefaults 已正确写入。但是,在返回开始视图时,已发布的绑定不会更新。有趣的是,UserDefaults 已更新。
主视图仅显示绑定值和用户默认值。
开始视图:
import SwiftUI
struct ContentView: View {
@State private var showUtilities = false
@ObservedObject var userDefaultManager = UserDefaultsManager()
var body: some View {
NavigationView {
VStack{
Group { //group 1
Text("Published userDefaultManager.name:")
Text("\(UserUtilities().makeSubString(stringIn: self.userDefaultManager.name, count: 24))")
.padding(.bottom, 30)
.lineLimit(0)
Text("UserDefaults.standard.value:")
Text("\(UserUtilities().makeSubString(stringIn: UserDefaults.standard.value(forKey: "name") as! String, count: 24))")
.padding(.bottom, 30)
.lineLimit(0)
Text("Published userDefaultsManager.enableBiometrics:")
Text(String(self.userDefaultManager.enableBiometrics))
.padding(.bottom, 30)
.font(.headline)
} //group 1
Group { //group 2
Text("UserDefaults.standard.bool:")
Text(String(UserDefaults.standard.bool(forKey: AppDelegate.eb)))
.padding(.bottom, 30)
.font(.headline)
Button(action: {
self.showUtilities.toggle()
}) {
Text("Show Utilities")
}
.frame(width: 200)
.padding()
.font(.headline)
}//group 2
}//vstack
.navigationBarTitle("Read the Values")
.sheet(isPresented: $showUtilities) {
UserUtilities()
}
}
}
}
第二种观点:
import SwiftUI
import Combine
struct UserUtilities: View {
@ObservedObject var userDefaultManager = UserDefaultsManager()
var body: some View {
NavigationView {
VStack {
Toggle(isOn: self.$userDefaultManager.enableBiometrics) {
Text("Enable Biometric Login")
}
.padding(EdgeInsets(top: 50, leading: 50, bottom: 30, trailing: 50))
//this does not update
Text("Published name is \(UserUtilities().makeSubString(stringIn: self.userDefaultManager.name, count: 24))")
.padding(EdgeInsets(top: 0, leading: 0, bottom: 30, trailing: 0))
Text("UserDefaults name is \(UserUtilities().makeSubString(stringIn: UserDefaults.standard.value(forKey: "name") as! String, count: 24))")
.padding(EdgeInsets(top: 0, leading: 0, bottom: 30, trailing: 0))
\\this does not update
Text("Published enableBiometrics is " + String(self.userDefaultManager.enableBiometrics) )
Text("UserDefaults is " + String(UserDefaults.standard.bool(forKey: AppDelegate.eb)) )
.padding(.bottom, 20)
Button(action: {
self.userDefaultManager.name = UUID().uuidString
}) {
Text("Change the Published name")
}
.padding()
.font(.headline)
}
.navigationBarTitle("User Utilities", displayMode: .inline)
}
}//body
func makeSubString(stringIn: String, count: Int) -> String {
if stringIn.count > count {
let modString = stringIn.dropFirst(count)
let returnString = String(modString)
return returnString
}
return "can't get substring"
}
}
我的用户默认管理器:
import SwiftUI
import Combine
class UserDefaultsManager: ObservableObject {
@Published var name = UserDefaults.standard.value(forKey: "name") as! String {
didSet {
UserDefaults.standard.set(self.name, forKey: "name")
}
}
@Published var enableBiometrics: Bool = UserDefaults.standard.bool(forKey: AppDelegate.eb) {
didSet {
UserDefaults.standard.set(self.enableBiometrics, forKey: AppDelegate.eb)
}
}
}
为了完整起见 - 在 AppDelegate 中:
static let eb = "enablebiometrics"
@ObservedObject var userDefaultManager = UserDefaultsManager()
在 didFinishLaunchingWithOptions 中:
if UserDefaults.standard.value(forKey: AppDelegate.eb) == nil {
UserDefaults.standard.set(false, forKey: AppDelegate.eb)
}
userDefaultManager.enableBiometrics = UserDefaults.standard.bool(forKey: AppDelegate.eb)
if UserDefaults.standard.value(forKey: "name") == nil {
UserDefaults.standard.set("set in AppDelegate", forKey: "name")
}
userDefaultManager.name = UserDefaults.standard.value(forKey: "name") as! String
任何指导将不胜感激。Xcode 11.3 (11C29)
解决方案
您正在使用 UserDefaultsManager 的 2 个实例。仅实例化一个并将其传递给第二个视图或将其添加到环境 (@EnvironmentObject) 以在所有视图中访问它。