如何通过操作更新 macOS Storyboard Cocoa 项目的 Window 标题？

Question

这是我的项目：

import Cocoa
import SwiftUI

var appName: String = "My App Name"

class ViewController: NSViewController {
    
    override func viewWillAppear() {
        let controller = NSHostingController(rootView: ContentView())
        self.view = controller.view
        self.view.window?.title = appName
    }

}

struct ContentView: View {
    
    var body: some View {
        VStack {
            Button("Change") {
                appName += " updated!"
                print(appName)
            }
        }
        .frame(width: 400.0, height: 300.0)
    }
}

我的目标是能够更新我的 window 标题，我能够更新保存我的应用程序名称的变量，但由于 viewWillAppear function 不会被触发，我无法在那里更新我的 window 标题。 我想在那里使用通知，但在这种情况下我不确定它是否正确，因为它需要发布和接收通知，解决这个问题的方法是什么？

Answer 1

您可以引入一个 ViewModel 将title存储为@Published并从 Button 操作更新该属性而不是全局appName 。 在您的主机 controller 中，您可以订阅title的更改，因为它是@Published并在视图模型的title属性更新时更新窗口的标题。

import Cocoa
import Combine
import SwiftUI

var appName: String = "My App Name"

final class ViewModel: ObservableObject {
  @Published var title: String = appName
}

class ViewController: NSViewController {

  private let viewModel = ViewModel()

  private var titleObservation: AnyCancellable?

  override func viewDidLoad() {
    super.viewDidLoad()

    // Observe the title of the view model and update the window's title whenever it changes
    titleObservation = viewModel.$title.sink { [weak self] newTitle in
      self?.view.window?.title = newTitle
    }
  }

  override func viewWillAppear() {
    let controller = NSHostingController(rootView: ContentView(viewModel: viewModel))
    self.view = controller.view
    self.view.window?.title = viewModel.title
  }

}

struct ContentView: View {
  @ObservedObject private var viewModel: ViewModel

  init(viewModel: ViewModel) {
    self.viewModel = viewModel
  }

  var body: some View {
    VStack {
      Button("Change") {
        viewModel.title += " updated!"
      }
    }
    .frame(width: 400.0, height: 300.0)
  }
}

或者，您可以简单地将Button操作的闭包从托管 controller 注入您的视图，并从闭包更新窗口的标题。

class ViewController: NSViewController {

  override func viewWillAppear() {
    let contentView = ContentView(
      onButtonTap: { // this closure will be executed every time Button is tapped
        appName += " updated!"
        self.view.window?.title = appName
        print(appName)
      }
    )
    let controller = NSHostingController(rootView: contentView)
    self.view = controller.view
    self.view.window?.title = appName
  }

}

struct ContentView: View {
  // Closure to execute when `Button` is tapped
  private let onButtonTap: () -> Void

  init(onButtonTap: @escaping () -> Void) {
    self.onButtonTap = onButtonTap
  }

  var body: some View {
    VStack {
      Button("Change", action: onButtonTap)
    }
    .frame(width: 400.0, height: 300.0)
  }
}