Question

我创建了一个名为ActiveQuiz的ObservableObject类，其中包含我想在多个视图之间共享的信息：

import Foundation

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

在其中一个视图中，我显示文本，如果点按该文本，则会增加迭代器，迭代器又会在文本移至问题数组中的下一个条目时更新文本：

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，用于显示迭代器的位置：

import SwiftUI

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

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

第一个视图中的文本正在按预期方式更新，但第二个视图中的迭代器保持在初始1 / x。

问题：作为Swift的新成员，我不明白为什么ObservableObject ActiveQuiz的共享状态没有在“观察”它的所有视图中更新。同样，对于新手来说，如果我还没有提供回答我所不知道的问题所需的任何信息，我深表歉意。

Answer 1

目前尚不清楚如何将这些视图一起使用，例如，对于其他人来说，添加ContentView会有所帮助。如我所见，您使用2个不同的ActiveQuiz实例。因此，您的Question结构有1个实例，您将其更新为迭代器，而QuestionCounter具有其自己的实例，该实例不会从第一个实例进行更新。我认为解决方案应该是对两个结构都使用@EnvironmentObject，就像这样（由于缺少代码，我简化了您的示例）：

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())
    }
}

，您将实现以下目标：

Swift 5：ObservedObject无法更新

1 个答案: