Swift 5: ObservedObject未更新

Question

我创建了一个名为ObservableObject的ActiveQuiz类，我希望在多个视图之间共享信息：

import Foundation

class ActiveQuiz: ObservableObject{
    @Published var iterator = 0
    @Published var questions = createQuiz()
}

在我显示的其中一个视图中，如果点击文本，迭代器就会增加迭代器，而迭代器在将文本移到问题数组中的下一个条目时会更新文本：

import SwiftUI

struct Question: View {
    @ObservedObject var activeQuiz = ActiveQuiz()

    var body: some View {
        Text(self.activeQuiz.questions[self.activeQuiz.iterator].countryInfo.capital)
            .font(.title)
            .onTapGesture(perform: {
                // increase iterator by 1 unless it's at the end, then put back to 0
                self.activeQuiz.iterator = self.activeQuiz.iterator + 1 == self.activeQuiz.questions.count ? 0 : self.activeQuiz.iterator + 1
            } )
    }
}

在另一个视图中，我有一个计数，它显示迭代器所在的位置：

import SwiftUI

struct QuestionCounter: View {
    @ObservedObject var activeQuiz = ActiveQuiz()

    var body: some View {
        Text(String(self.activeQuiz.iterator + 1) + "/" + String(self.activeQuiz.questions.count))
    }
}

来自第一个视图的文本正在按预期更新，但是来自第二个视图的迭代器保持在初始的1/x。

updating ：作为一个新的Swift，我不明白为什么ObservableObject ActiveQuiz的共享状态没有在所有正在“观察”它的视图中更新。另外，对于斯威夫特来说，如果我没有包括任何必要的信息来回答我不知道的问题，我很抱歉。

Answer 1

目前还不清楚如何将这些视图放在一起使用，例如，添加ContentView对其他人可能会有帮助。正如我所看到的，您使用了两个不同的ActiveQuiz实例。因此，您的Question结构有一个实例，您可以更新它的迭代器，而QuestionCounter有它自己的实例，它不是从第一个实例中更新的。我认为解决方案应该是对这两个结构使用@EnvironmentObject (我简化了示例，因为缺少代码)：

import SwiftUI
import Combine

class ActiveQuiz: ObservableObject {
    @Published var iterator = 0
}

struct UsingEnvironmentObject: View {

    @EnvironmentObject var activeQuiz: ActiveQuiz
    var body: some View {
        VStack {

            Question() // it will take EnvironmentObject from parent
            QuestionCounter() // this one will take the same EnvironmentObject from parent

        }
    }
}

// more representative solution
struct UsingEnvironmentObject: View {

    @ObservedObject var activeQuiz = ActiveQuiz()

    var body: some View {
        VStack {
            // here you see, that both structs use one instance
            Question()
                .environmentObject(activeQuiz)
            QuestionCounter()
                .environmentObject(activeQuiz)

        }
    }
}

struct Question: View {

    @EnvironmentObject var activeQuiz: ActiveQuiz

    var body: some View {
        Text("some text from question")
            .font(.title)
            .onTapGesture(perform: {
                // increase iterator by 1 unless it's at the end, then put back to 0
                self.activeQuiz.iterator = self.activeQuiz.iterator + 1 == 10 ? 0 : self.activeQuiz.iterator + 1
            } )
    }
}

struct QuestionCounter: View {
    @EnvironmentObject var activeQuiz: ActiveQuiz

    var body: some View {
        Text(String(self.activeQuiz.iterator + 1) + "/10")
    }
}



struct UsingEnvironmentObject_Previews: PreviewProvider {
    static var previews: some View {
        UsingEnvironmentObject()
        .environmentObject(ActiveQuiz())
    }
}

你们将实现这一目标：

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