ObservableObject中@Published更新后SwiftUI View未刷新问题排查

我知道已有很多类似问题，但大多是引用/值类型的问题，我的情况不一样。我通过UIHostingController在UIViewController中嵌入了SwiftUI视图，使用了ObservableObject类型的ViewModel，这个ViewModel在ViewController中实例化后传递给SwiftUI视图。但更新ObservableObject中的@Published属性时，SwiftUI视图并未同步刷新，请问哪里出错了？

ViewController代码 #

class DeveloperScreenViewController1: UIViewController {
let developerScreenViewModel: DeveloperScreenViewModel

private lazy var contentView: UIHostingController = {
    UIHostingController(rootView: DeveloperScreenView(developerScreenViewModel: developerScreenViewModel))
}()

init(viewModel: DeveloperScreenViewModel) {
    self.developerScreenViewModel = viewModel
    super.init(nibName: nil, bundle: Bundle.main)
}


override func viewDidLoad() {
    super.viewDidLoad()
     setupConstraints()

}

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    self.developerScreenViewModel.setup()
}

private func setupConstraints() {
    // add swiftUI view as a subview
    addChild(self.contentView)
    self.contentView.view.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(self.contentView.view)
    
    // set constraints to match the parent viewcontroller's view
    NSLayoutConstraint.activate([
        view.leadingAnchor.constraint(equalTo: contentView.view.leadingAnchor),
        view.trailingAnchor.constraint(equalTo: contentView.view.trailingAnchor),
        view.topAnchor.constraint(equalTo: contentView.view.topAnchor),
        view.bottomAnchor.constraint(equalTo: contentView.view.bottomAnchor)
    ])
}

ViewModel代码 #

class DeveloperScreenViewModel: ObservableObject {

 @Published var environments: [Endpoint] = []
 @Published var realTimeUpdateToggle:Bool = false


public init() {
    // self.setup()
}

public func setup() {
    self.initializeListItems()
    self.initializeRealTimeToggle()
}

private func initializeListItems() {
    self.environments = EnvironmentStore.shared.changeableEndpoints
}

func initializeRealTimeToggle() {
   realTimeUpdateToggle = RealTimeUpdatesDeveloperUtils.isEnabled()
}

SwiftUI View代码 #

struct DeveloperScreenView: View {

@ObservedObject var developerScreenViewModel: DeveloperScreenViewModel


var body: some View { 
            VStack {
                
                DeveloperScreenEnvironmentView(endPoints: developerScreenViewModel.environments)
                
                
                DeveloperScreenRealTimeUpdateToggleView(realTimeToggleItem: developerScreenViewModel.realTimeUpdateToggle)
                
            }            
}

问题原因及修复方案 #

核心问题1：子视图接收的是值拷贝而非绑定 #

你的DeveloperScreenEnvironmentView和DeveloperScreenRealTimeUpdateToggleView直接接收的是属性的值拷贝，没有和ViewModel建立响应式关联。当ViewModel的@Published属性更新时，子视图持有的是旧值的副本，自然无法感知变化。

核心问题2：布局约束方向写反 #

setupConstraints中的约束逻辑错误，将父视图的锚点绑定到子视图，会导致布局异常，甚至可能隐藏SwiftUI视图（虽不是刷新失效的直接原因，但会引发其他UI问题）。

具体修复步骤： #

1. 子视图改用Binding传递参数
   修改子视图的输入参数为Binding类型，让它们直接绑定到ViewModel的@Published属性：

   // 修改DeveloperScreenEnvironmentView
   struct DeveloperScreenEnvironmentView: View {
       @Binding var endPoints: [Endpoint]
       // 其余视图逻辑保持不变
   }
   
   // 修改DeveloperScreenRealTimeUpdateToggleView
   struct DeveloperScreenRealTimeUpdateToggleView: View {
       @Binding var realTimeToggleItem: Bool
       // 其余视图逻辑保持不变
   }
   
   // 父SwiftUI视图中传递绑定
   struct DeveloperScreenView: View {
       @ObservedObject var developerScreenViewModel: DeveloperScreenViewModel
   
       var body: some View { 
           VStack {
               DeveloperScreenEnvironmentView(endPoints: $developerScreenViewModel.environments)
               DeveloperScreenRealTimeUpdateToggleView(realTimeToggleItem: $developerScreenViewModel.realTimeUpdateToggle)
           }            
       }
   }
   

2. 修正布局约束方向
   调换锚点绑定顺序，确保子视图对齐父视图的边缘：

   NSLayoutConstraint.activate([
       contentView.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
       contentView.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
       contentView.view.topAnchor.constraint(equalTo: view.topAnchor),
       contentView.view.bottomAnchor.constraint(equalTo: view.bottomAnchor)
   ])
   

3. 可选：确保更新在主线程执行
   如果setup方法或后续属性更新是在后台线程触发的，必须切换到主线程——@Published的通知必须在主线程发送，否则SwiftUI无法正确刷新：

   public func setup() {
       DispatchQueue.main.async {
           self.initializeListItems()
           self.initializeRealTimeToggle()
       }
   }
   

内容的提问来源于stack exchange，提问作者SpaceDust__