How can I update my Window title for macOS Storyboard Cocoa project via an action?-CodePudding

This is my project:

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)
    }
}

My goal is be able to update my window title, I am be able to update the variable that holds my app name but since viewWillAppear function would not be triggered I am unable to update my window title there. I was thinking to use a notification there but in this case I am not sure if it is the right feet there, because it would need to post and receive notification, what is the approach for solving this problem?

CodePudding user response：

You can introduce a ViewModel storing title as @Published and from the Button action update that property rather than a global appName. In your hosting controller, you can subscribe to changes of title, since it is @Published and update the window's title whenever the view model's title property is updated.

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)
  }
}

Alternatively, you can simply inject a closure for the Button action into your view from the hosting controller and update the window's title from the closure.

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)
  }
}