如何使用 class 函数编辑环境对象？

Question

我是 swift 编程新手。我试图通过 class 函数专门更改环境对象的值来尝试使用环境对象来更新视图。我在内容视图中有两个子视图，因为我希望在 UserData 环境对象中更改字符串时查看两个子视图是否一起更新。

但是，出现错误 'Thread 1: Fatal error: No ObservableObject of type UserData found. A View.environmentObject(_:) for UserData may be missing ...'

在SceneDelagate.swift中，我注入了环境对象：

let userData = UserData()

window.rootViewController = UIHostingController(rootView:contentView.environmentObject(userData))

UserData.swift

final class UserData: ObservableObject {

    @Published var image: UIImage? = nil
    @Published var string  = "" 



}

StringGenerator.swift

class StringGenerator {

    @EnvironmentObject var userData: UserData


    func changeURL(){
        print("Changing string now from \(userData.string)")
        if self.userData.string == "HELLO"{
            self.userData.string = "BYE"

        }
        else{
            self.userData.string = "HELLO"
        }
        print("to \(userData.string)")
    }
}

SubView1.swift

struct SubView1: View {
    @EnvironmentObject var userData: UserData



    var body: some View {
        Text("\(userData.string)")

    }
}

SubView2.swift

struct SubView2: View {
    @EnvironmentObject var userData: UserData



    var body: some View {
        Text("\(userData.string)")

    }
}

ContentView.swift

struct ContentView: View {
    @EnvironmentObject var userData: UserData

    let stringGenerator = StringGenerator()

    var body: some View {

        VStack{

            Button(action: {
                print("Changing Text Now !")
                self.stringGenerator.changeURL()
                print("\(self.userData.string)")
            }) {
                Text("Change Text ")
            }


            SubView1()
            SubView2()


        }


    }
}

一般来说，我想知道如何通过 class 函数更改环境对象。

当我运行代码崩溃时。这里有什么问题？

Answer 1

这是一个解决方案：

1) 在内容视图中

struct ContentView: View {
    @EnvironmentObject var userData: UserData

    let stringGenerator: StringGenerator   // declare-only

2) 在生成器中

class StringGenerator {

    var userData: UserData   // just member
    init(userData: UserData) {
      self.userData = userData
    }

3) 在场景代理中

let userData = UserData()

// inject generator via constructor with same user data
let contentView = ContentView(stringGenerator: 
                              StringGenerator(userData: userData))

window.rootViewController = UIHostingController(rootView: 
                              contentView.environmentObject(userData))

如何使用 class 函数编辑环境对象？

How to use edit an environment object from a class function?

observable

ios

swift

swiftui

environmentobject