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ios - @EnvironmentObject 可以与不是视图的普通结构一起使用吗？

问题描述

我在将类信息从一个结构实例传递到另一个结构实例时遇到了麻烦，所以我一直在搞砸尝试。

这有效，因为我正在通过 Views

// phone_testingApp.swift
import SwiftUI

@main
struct phone_testingApp: App {
    
    @ObservedObject var myObservedObject = MyObservedObject()
    
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(myObservedObject)
        }
    }
}

// ContentView.swift

import SwiftUI
import Combine

struct ContentView: View {
    
    var subtract = MinusToObject()
    @EnvironmentObject var myNumber: MyObservedObject
    
    var body: some View {
        VStack{

            Text("The number is \(myNumber.theObservedObjectToPass)")
            
            MinusToObject()
                .environmentObject(myNumber)
        }
    }
}

class MyObservedObject: ObservableObject {
    @Published var theObservedObjectToPass = 5
}

struct MinusToObject: View {
    
    @EnvironmentObject var theObservedObject: MyObservedObject
    
    var body: some View {
        Text("Minus")
            .onTapGesture {
                theObservedObject.theObservedObjectToPass -= 1
            }
    }
}

但是如果我只使用一个不符合 View 这样的普通结构尝试类似的东西

import SwiftUI
import Combine

struct ContentView: View {
    
    var subtract = MinusToObject()
    @EnvironmentObject var myNumber: MyObservedObject
    
    var body: some View {
        VStack{

            Text("The number is \(myNumber.theObservedObjectToPass)")
            
            Text("Minus")
                .onTapGesture {
                    subtract.subtractIt()
                }
        }
    }
}

class MyObservedObject: ObservableObject {
    @Published var theObservedObjectToPass = 5
}

struct MinusToObject {
    
    @EnvironmentObject var theObservedObject: MyObservedObject
    
        
            func subtractIt() {
                theObservedObject.theObservedObjectToPass -= 1 //Thread 1: Fatal error: No ObservableObject of type MyObservedObject found. A View.environmentObject(_:) for MyObservedObject may be missing as an ancestor of this view.
            }
}

我收到一个运行时错误，这是我在调用函数时添加的注释。

我对如何传递引用类型的实例感到很困惑，所以我确信我做错了很多事情，任何帮助将不胜感激。

标签： iosswiftswiftui

解决方案

这是行不通的，因为EnvironmentObject注入是在 SwiftUIView层次结构上仅对所有基于视图的子对象执行的。

如果您希望任何旧对象访问共享实例，则必须手动创建一个单例并将其注入 SwiftUI 视图层次结构。

class MyObservedObject: ObservableObject {
    static let shared = MyObservedObject()
    private init() { }

    @Published var theObservedObjectToPass = 5
}

/// you can use it in a plain object
struct MinusToObject {
    func subtractIt() {
        MyObservedObject.shared.theObservedObjectToPass -= 1 
    }
}

// you can use it in a view
struct ContentView: View {
    var body: some View {
        SomeOtherView()
            .environmentObject(MyObservedObject.shared)
    }
}

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