Question

您好吗？有一种简单的方法可以将值作为EnvironmentObject放在UserDefaults中以显示在其他视图中？类似于在SettingsView中设置用户名并显示在DashboardView中。非常感谢

Answer 1

最后找到它How do I use UserDefaults with SwiftUI?

答案仅基于Bool。她也是使用String的解决方案。

ContentView设置了TabView：

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

布尔的UserSettings和字符串的UserName

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)
        }
    }
}

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)")
    }
}

第二视图设置，其中设置了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()
    }
}

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

1 个答案: