尽管使用SWIFT游乐场自己的代码，但我无法在所有视图中更新数组

Question

我是新来的所以请原谅我。

我正在iPad上学习斯威夫特游乐场教程。他们很好，但有点小马车。

我遵守了教程。我应该用代码来显示5个生物，他们的名字和表情符号。我可以按add键转到另一个视图并将更多内容添加到列表中。如果我将一个ForEach代码放入add视图，我可以看到列表更新。但在其他视图中，它似乎没有更新。当我来回导航的时候，更新就消失了。

本教程让我们使用附加项将项目添加到列表中。使用EnvironmentObject包装器调用列表。我在网上搜索了一下，找不到出什么问题了。

有人能帮忙吗？

谢谢

代码中的代码演练注释似乎是在从应用程序复制时自动添加的。

第一个文件: CreatureZoo

import SwiftUI

//#-learning-task(creatureZoo)

/*#-code-walkthrough(creatureZoo.observableObject)*/
class CreatureZoo : ObservableObject {
    /*#-code-walkthrough(creatureZoo.observableObject)*/
    /*#-code-walkthrough(creatureZoo.creatures)*/
    /*#-code-walkthrough(creatureZoo.published)*/ @Published /*#-code-walkthrough(creatureZoo.published)*/var creatures = [
        /*#-code-walkthrough(creatureZoo.creature)*/
        Creature(name: "Gorilla", emoji: ""),
        /*#-code-walkthrough(creatureZoo.creature)*/
        Creature(name: "Peacock", emoji: ""),
        Creature(name: "Squid", emoji: ""),
        Creature(name: "Owl", emoji: ""),
        Creature(name: "Unicorn", emoji: "")
        //#-learning-task(addCreatures)
        
    ]
    /*#-code-walkthrough(creatureZoo.creatures)*/
}

/*#-code-walkthrough(creatureZoo.creatureStruct)*/
struct Creature : Identifiable {
    var name : String
    var emoji : String
    
    var id = UUID()
    var offset = CGSize.zero
    var rotation : Angle = Angle(degrees: 0)
}
/*#-code-walkthrough(creatureZoo.creatureStruct)*/


// Should be hidden probably
extension CreatureZoo {
    func randomizeOffsets() {
        for index in creatures.indices {
            creatures[index].offset = CGSize(width: CGFloat.random(in: -200...200), height: CGFloat.random(in: -200...200))
            creatures[index].rotation = Angle(degrees: Double.random(in: 0...720))
        }
    }
    
    func synchronizeOffsets() {
        let randomOffset = CGSize(width: CGFloat.random(in: -200...200), height: CGFloat.random(in: -200...200))
        for index in creatures.indices {
            creatures[index].offset = randomOffset
        }
    }
    
    func indexFor(_ creature: Creature) ->  Double {
        if let index = creatures.firstIndex(where: { $0.id == creature.id }) {
            return Double(index)
        }
        return 0.0
    }
}

第二文件CreatureRow

import SwiftUI

struct CreatureRow: View {
    var creature : Creature
    
    var body: some View {
        HStack {
            Text(creature.name)
                .font(.title)
            
            Spacer()
            
            Text(creature.emoji)
                .resizableFont()
                .frame(minWidth: 125)
        }
        
        
    }
}

struct CreatureRow_Previews: PreviewProvider {
    static var previews: some View {
        CreatureRow(creature: Creature(name: "Dodo Bird", emoji: ""))
    }
}

第3文件CreatureEditor

import SwiftUI
import Guide

struct CreatureEditor: View {
    //#-learning-task(defineVariablesCreatureEditor)
    @Environment(\.dismiss) var dismiss
    
    @State var newCreature : Creature = Creature(name: "", emoji: "")
    @EnvironmentObject var data : CreatureZoo
    var body: some View {
        SPCAssessableGroup(view: self) {
            
            
            VStack(alignment: .leading) {
                
                
                Form {
                    Section("Name") {
                        //#-learning-task(addACreatureEditorTextField)
                        TextField("Creature Name", text: $newCreature.name)
                    }   
                    
                    Section("Emoji") {
                        TextField("Emoji", text: $newCreature.emoji)
                        
                    }
                    
                    Section("Creature Preview") {
                        CreatureRow(creature: newCreature)
                    }
                    
                    Section("Current Creatures") {
                        ForEach(data.creatures) { creature in 
                            
                            CreatureRow(creature: creature)
                            /*#-code-walkthrough(forEach.id)*/
                            
                        }
                        
                    }
                }
                
                
            }
            
            
            .toolbar { 
                ToolbarItem { 
                    Button("Add") { 
                        data.creatures.append(newCreature)
                        dismiss()
                        
                        
                    }
                }
            }
            
        }.environmentObject(CreatureZoo()) // I added this myself to try to make things work 
    }
    
}

struct CreatureEditor_Previews: PreviewProvider {
    static var previews: some View {
        NavigationView() {
            CreatureEditor().environmentObject(CreatureZoo())
        }
    }
}

第4文件contentView

import SwiftUI
import Guide

struct ContentView: View {
    
    @EnvironmentObject var data : CreatureZoo
    
    //#-learning-task(cleanUpApp)
    //#-learning-task(createYourOwn)

    var body: some View {
        SPCAssessableGroup(view: self) {
            List {
                
                Text("ContentView")
                
                Section("Dance") {
                    NavigationLink("make the creatures dance") {
                        DancingCreatures()
                            .navigationTitle("Dancing Creatures")
                            .environmentObject(CreatureZoo())
                    }
                    //#-learning-task(addNavLinkCreatureDance)
                    
                }
                /*#-code-walkthrough(forEach.id)*/
                Section("Add new creature") {
                    NavigationLink(" Add new") {
                        
                        CreatureEditor()
                            .navigationTitle("Add new")
                            .environmentObject(CreatureZoo())
                        
                    }
                    
                }
                ForEach(data.creatures) { creature in 
                    
                    CreatureRow(creature: creature)
                    /*#-code-walkthrough(forEach.id)*/
                    
                }
                
                .onDelete { indexSet in 
                    data.creatures.remove(atOffsets: indexSet)
                }
                
                                
            }
            .toolbar { 
                ToolbarItem { 
                    NavigationLink("Add") { 
                        CreatureEditor()
                            .navigationTitle("Add new creature")
                            .environmentObject(CreatureZoo())
                    }
                }
            }
            
        }
    }
}

第5文件myApp

import SwiftUI
import Guide
//#-learning-task(myApp)

@main
/*#-code-walkthrough(myApp.appProtocol)*/
struct MyApp: App {
    /*#-code-walkthrough(myApp.appProtocol)*/
    @StateObject var data = CreatureZoo()
    /*#-code-walkthrough(myApp.body)*/
    var body: some Scene {
        SPCAssessableWindowGroup(app: self, assessmentCandidates: [CreatureZoo()]) {
            NavigationView { 
                
                
                ContentView()
                    .navigationTitle("My Creatures")
                    .environmentObject(data)
                
            }
            
                
            }
            

            /*#-code-walkthrough(myApp.contentView)*/
            
            /*#-code-walkthrough(myApp.contentView)*/

        }
    }
    /*#-code-walkthrough(myApp.body)*/

Answer 1

当您添加.environmentObject(CreatureZoo())时，您将创建一个在视图之间不共享的新实例。您应该在.environmentObject文件中添加一次App。

在ContentView中，这个.environmentObject(CreatureZoo())应该是.environmentObject(data)。