SwiftUI 在 UserDefaults 中设置字符串值，但作为`EnvironmentObject`

Posted 2023-02-24

【中文标题】SwiftUI 在 UserDefaults 中设置字符串值，但作为`EnvironmentObject`

【英文标题】：SwiftUI set string value inside UserDefaults but as a `EnvironmentObject`

【发布时间】：2020-02-06 20:19:36

【问题描述】：

您好，是否有一种简单的方法可以将 UserDefaults 中的值作为EnvironmentObject 显示在其他视图中？在 SettingsView 中设置用户名并显示在 DashboardView 中。非常感谢

【参考方案1】：

终于找到How do I use UserDefaults with SwiftUI?

答案仅基于Bool。她也是String 的解决方案。

使用 TabView 设置的 ContentView：

import SwiftUI

struct ContentView: View 
    var body: some View 
        VStack 
            TabView
                Dashboard(userName: UserName())
                    .tabItem(
                        Image(systemName: "rectangle.3.offgrid")
                        Text("Dashboard")
                    )
                Settings()
                    .tabItem(
                        Image(systemName: "gear")
                        Text("Einstellungen")
                    )
            
        
    


#if DEBUG
struct ContentView_Previews: PreviewProvider 
    static var previews: some View 
        ContentView()
    

#endif

布尔型的用户设置和字符串的用户名

import SwiftUI
import Combine


final class UserSettings: ObservableObject 

    let objectWillChange = PassthroughSubject<Void, Never>()

    @UserDefault("ShowOnStart", defaultValue: true)
    var showOnStart: Bool 
        willSet 
            objectWillChange.send()
        
    


final class UserName: ObservableObject 

    let objectWillChange = PassthroughSubject<Void, Never>()

    @UserDefault("userName", defaultValue: "UknowName")
    var userNameSet: String 
        willSet 
            objectWillChange.send()
        
    

在 UserSettings 和 UserName 类中使用的属性包装器 UserDefaults

@propertyWrapper
struct UserDefault<T> 
    let key: String
    let defaultValue: T

    init(_ key: String, defaultValue: T) 
        self.key = key
        self.defaultValue = defaultValue
    

    var wrappedValue: T 
        get 
            return UserDefaults.standard.object(forKey: key) as? T ?? defaultValue
        
        set 
            UserDefaults.standard.set(newValue, forKey: key)
        
    

那里的第一个视图仪表板显示了在设置视图中所做的更改

import SwiftUI

struct Dashboard: View 
    @ObservedObject var settings = UserSettings()
    @ObservedObject var userName = UserName()
    var body: some View 
        VStack
            Text("hallo")

            ExtractedViewName(userName: userName)
                ExtractedView(settings: settings)

        
    


struct Dashboard_Previews: PreviewProvider 
    static var previews: some View 
        Dashboard(userName: UserName())
    


struct ExtractedView: View 
    @ObservedObject var settings : UserSettings
    var body: some View 
        VStack
        if settings.showOnStart
        Text("Welcome")
        
        
    


struct ExtractedViewName: View 
    @ObservedObject var userName : UserName
    var body: some View 
        Text("Test One: \(userName.userNameSet)")
    

那里的第二个视图设置设置显示在仪表板视图中的更改

import SwiftUI

struct Settings: View 
   @ObservedObject var settings = UserSettings()
@ObservedObject var userName = UserName()
    @State private var userTextfield = ""
    var body: some View 
        VStack 
            Toggle(isOn: $settings.showOnStart) 
                Text("Show welcome text")
            
            TextField("Name", text: $userTextfield)
                self.userName.userNameSet = self.userTextfield
            
            Button(action: 
                print("\(self.userName.userNameSet)")
            ) 
                Text("Button")
            
        
        


struct Settings_Previews: PreviewProvider 
    static var previews: some View 
        Settings()