Swift '；致命错误：索引超出范围'；删除视图中的绑定对象时

在修改子视图依赖于绑定对象的数组时，我在避免索引超出范围错误方面遇到了一些问题

我有一个名为WorkoutList的父视图。WorkoutList具有ActiveWorkoutStore的EnvironmentObject。ActiveWorkoutStore是一个ObservableObject，具有一系列训练对象。我有一个从ActiveWorkoutStore检索的活动训练列表。我使用ForEach循环处理这些活动训练的索引，并将对象绑定传递到名为EditWorkout的子视图，作为NavigationLink的目标。EditWorkout有一个完成训练的按钮，该按钮将其从ActiveWorkoutStore的训练数组中删除，并将其添加到WorkoutHistoryStore。当我从ActiveWorkoutStore的activeWorkouts数组中删除此对象时，我遇到了麻烦，立即导致索引超出范围错误。我怀疑这是因为活动视图依赖于我刚刚删除的绑定对象。我尝试了几种方法，包括将训练传递给EditWorkout，然后使用其id引用ActiveWorkoutStore中的训练来执行我的操作，但遇到了类似的问题。我在网上看到过很多这样的例子，即利用ForEach迭代索引，我已经尽我所能反映了这一点，但我怀疑我可能忽略了这种方法的细微差别

我在下面附上了代码示例。如果您有任何问题或者我还有什么需要包括的，请告诉我！提前感谢您的帮助

工作列表（父视图） 编辑训练（子视图） 运动训练商店 训练

ForEach

为常量范围容器（注意下面的构造函数描述），不允许在构造后修改

扩展ForEach，其中Data==Range，ID==Int，Content:View{
///创建一个实例，该实例通过*常量按需计算视图*
///射程。
///
///此实例只读取'data'的初始值，因此不读取
///需要跨更新识别视图。
///
///要在动态范围内按需计算视图，请使用
///`ForEach（uq:id:content:）`。
public init（u数据：范围，@ViewBuilder内容：@escaping（Int）->content）
}

---

如果要修改容器，必须使用ForEach（activeWorkout.exercises）

中的内容

WorkoutExercise

，

EditWorkoutExercise

，

WorkoutHistoryStore

，

ExerciseStore

？也许最好清理一下这段代码，只留下重要的东西？一般来说，从列表中删除东西风险更大，因为最终可能会出现您描述的问题。更好的方法可能是有一个训练列表，然后为每个训练设置一个workoutState变量（可以是枚举workoutState），该变量可以是“活动”或“完成”。然后，任何需要此数组数据的视图都可以对workoutState变量使用筛选器。您可以在视图中添加

if activeWorkout.exerces.index.count>0{//Render List}else{//Render something}

，以检查是否有任何要渲染的内容，同时保持

@Published

变量的简单性。。。

训练

对象中的数组未发布@是的，抱歉。。。更多的上下文总是有用的！我想我已经找到了答案，并且非常喜欢阿达胡斯推荐的方法，因此我将继续前进。：）@阿达胡斯：我喜欢这个概念。我要做这个改变！非常感谢。非常感谢你。我没有注意到这一点，这确实澄清了我为什么会遇到这个问题。当我将此添加到代码中时，我遇到了“初始化器需要一个主体”错误。知道为什么会发生这种情况吗？

import SwiftUI

struct WorkoutList: View {
    @EnvironmentObject var activeWorkoutsStore: ActiveWorkoutStore
    @State private var addExercise = false
    @State private var workoutInProgress = false

    var newWorkoutButton: some View {
        Button(action: {
            self.activeWorkoutsStore.newActiveWorkout()
        }) {
            Text("New Workout")
            Image(systemName: "plus.circle")
        }
    }

    var body: some View {
        NavigationView {
            Group {
                if activeWorkoutsStore.activeWorkouts.isEmpty {
                    Text("No active workouts")
                } else {
                    List {
                        ForEach(activeWorkoutsStore.activeWorkouts.indices.reversed(), id: \.self) { activeWorkoutIndex in
                            NavigationLink(destination: EditWorkout(activeWorkout: self.$activeWorkoutsStore.activeWorkouts[activeWorkoutIndex])) {
                                Text(self.activeWorkoutsStore.activeWorkouts[activeWorkoutIndex].id.uuidString)
                            }
                        }
                    }
                }
            }
            .navigationBarTitle(Text("Active Workouts"))
            .navigationBarItems(trailing: newWorkoutButton)
        }
    }
}

//
//  EditWorkout.swift
//  workout-planner
//
//  Created by Dominic Minischetti III on 11/2/19.
//  Copyright © 2019 Dominic Minischetti. All rights reserved.
//

import SwiftUI

struct EditWorkout: View {
    @EnvironmentObject var workoutHistoryStore: WorkoutHistoryStore
    @EnvironmentObject var activeWorkoutStore: ActiveWorkoutStore
    @EnvironmentObject var exerciseStore: ExerciseStore
    @Environment(\.presentationMode) var presentationMode
    @State private var addExercise = false
    @Binding var activeWorkout: Workout
    
    var currentDayOfWeek: String {
        let weekdayIndex = Calendar.current.component(.weekday, from: Date())
        return Calendar.current.weekdaySymbols[weekdayIndex - 1]
    }

    var chooseExercisesButton: some View {
        Button (action: {
            self.addExercise = true
        }) {
            HStack {
                Image(systemName: "plus.square")
                Text("Choose Exercises")
            }
        }
        .sheet(isPresented: self.$addExercise) {
            AddWorkoutExercise(exercises: self.$activeWorkout.exercises)
                .environmentObject(self.exerciseStore)

        }
    }
    
    var saveButton: some View {
        Button(action: {
            self.workoutHistoryStore.addWorkout(workout: self.$activeWorkout.wrappedValue)
            self.activeWorkoutStore.removeActiveWorkout(workout: self.$activeWorkout.wrappedValue)
            self.presentationMode.wrappedValue.dismiss()
        }) {
            Text("Finish Workout")
        }
        .disabled(self.$activeWorkout.wrappedValue.exercises.isEmpty)
    }

    var body: some View {
        Form {
            Section(footer: Text("Choose which exercises are part of this workout")) {
                chooseExercisesButton
            }
            Section(header: Text("Exercises")) {
                if $activeWorkout.wrappedValue.exercises.isEmpty {
                    Text("No exercises")
                } else {
                    ForEach(activeWorkout.exercises.indices, id: \.self) { exerciseIndex in
                        NavigationLink(destination: EditWorkoutExercise(exercise: self.$activeWorkout.exercises[exerciseIndex])) {
                            VStack(alignment: .leading) {
                                Text(self.activeWorkout.exercises[exerciseIndex].name)
                                Text("\(self.activeWorkout.exercises[exerciseIndex].sets.count) Set\(self.activeWorkout.exercises[exerciseIndex].sets.count == 1 ? "" : "s")")
                                    .font(.footnote)
                                    .opacity(0.5)
                            }
                        }
                    }
                    saveButton
                }
            }
        }
        .navigationBarTitle(Text("Edit Workout"), displayMode: .inline )
    }
}

import Foundation
import Combine

class ActiveWorkoutStore: ObservableObject {
    @Published var activeWorkouts: [Workout] = []
    
    func newActiveWorkout() {
        activeWorkouts.append(Workout())
    }
    
    func saveActiveWorkout(workout: Workout) {
        let workoutIndex = activeWorkouts.firstIndex(where: { $0.id == workout.id })!
        
        activeWorkouts[workoutIndex] = workout
    }
    
    func removeActiveWorkout(workout: Workout) {
        if let workoutIndex = activeWorkouts.firstIndex(where: { $0.id == workout.id }) {
            activeWorkouts.remove(at: workoutIndex)
        }
    }
}

import SwiftUI

struct Workout: Hashable, Codable, Identifiable {
    var id = UUID()
    var date = Date()
    var exercises: [WorkoutExercise] = []
}

extension ForEach where Data == Range<Int>, ID == Int, Content : View {

    /// Creates an instance that computes views on demand over a *constant*
    /// range.
    ///
    /// This instance only reads the initial value of `data` and so it does not
    /// need to identify views across updates.
    ///
    /// To compute views on demand over a dynamic range use
    /// `ForEach(_:id:content:)`.
    public init(_ data: Range<Int>, @ViewBuilder content: @escaping (Int) -> Content)
}