在SwiftUI中將值從App傳遞到ContentView

我找到了很多關于如何讓用戶選擇選單項然后打開檔案夾的資源。以下是我所擁有的。

import SwiftUI

@main
struct Oh_My_App: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
                .frame(width: 480.0, height: 320.0)
        }.commands {
            CommandGroup(after: .newItem) {
                Button {
                    if let url = showFileOpenPanel() {
                        print(url.path)
                    }
                } label: {
                    Text("Open file...")
                }
                .keyboardShortcut("O")
            }
        }
    }
    
    func showFileOpenPanel() -> URL? {
        let openPanel = NSOpenPanel()
        openPanel.canChooseDirectories = true
        openPanel.canCreateDirectories = false
        openPanel.canChooseFiles = false
        openPanel.title = "Selecting a folder..."
        openPanel.message = "Please select a folder containing one or more files."
        let response = openPanel.runModal()
        return response == .OK ? openPanel.url : nil
    }
}

好的。那沒問題。我可以列印檔案路徑。好吧，我的實際問題是如何將此值回傳到ContentView？這是ContentView虛擬地運行在此示例應用程式展示。所以我使用ObservableObject如下。

import SwiftUI

@main
struct Oh_My_App: App {
    @StateObject var menuObservable = MenuObservable()
    @NSApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
    
    var body: some Scene {
        WindowGroup {
            ContentView()
        }.commands {
            CommandGroup(after: .newItem) {
                Button {
                    menuObservable.openFile()
                } label: {
                    Text("Open file...")
                }
                .keyboardShortcut("O")
            }
        }
    }
}

class MenuObservable: ObservableObject {
    @Published var fileURL: URL = URL(fileURLWithPath: "")
    func openFile() {
        if let openURL = showFileOpenPanel() {
            fileURL = openURL
        }
    }
    
    func showFileOpenPanel() -> URL? {
        let openPanel = NSOpenPanel()
        openPanel.canChooseDirectories = true
        openPanel.canCreateDirectories = false
        openPanel.canChooseFiles = false
        openPanel.title = "Selecting a folder..."
        openPanel.message = "Please select a folder containing one or more files."
        let response = openPanel.runModal()
        return response == .OK ? openPanel.url : nil
    }
}
// ContentView.swift //
import SwiftUI

struct ContentView: View {
    @ObservedObject var menuObservable = MenuObservable()
    @State var filePath: String = ""
    
    var body: some View {
        ZStack {
            VStack {
                Text("Hello: \(filePath)")
            }.onChange(of: menuObservable.fileURL) { newValue in
                filePath = newValue.path
            }
        }
    }
}

我的ContentView不會更新。那么我如何ContentView從選單呼叫中接收一個值App呢？謝謝。

uj5u.com熱心網友回復：

現在，你要創建一個新的實體中MenuObservable的ContentView，所以它并沒有給收到選單命令實體的任何連接。您需要傳遞對現有實體的參考（即由 擁有的實體Oh_My_App）。

在您的 中ContentView，更改@ObservedObject var menuObservable = MenuObservable()為：

@ObservedObject var menuObservable : MenuObservable

在你的Oh_My_App：

WindowGroup {
    ContentView(menuObservable: menuObservable)
}

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