如何回傳View以編輯其屬性？

我正在創建一個回傳其編輯器視圖的類。但是遇到了錯誤

無法將“Published.Publisher”型別的值轉換為預期的引數型別“Binding”

這是 Playgrounds 的簡單測驗代碼。

import SwiftUI
import PlaygroundSupport


struct EditorView: View {
    @Binding var text: String

    var body: some View {
        HStack {
            Text("Name:")
            TextField("Jerry", text: $text)
        }
    }
}

class MyModel: ObservableObject {
    @Published var name: String = "Tom"

    func editorView() -> some View {
        EditorView(text: $name) // [ERROR] Cannot convert value of type 'Published.Publisher' to expected argument type 'Binding<String>'
    }
}

struct ContentView: View {
    @StateObject var model: MyModel = .init()

    var body: some View {
        model.editorView()
    }
}

struct ContentView_Preview: PreviewProvider {
    static var previews: some View {
        ContentView()
            .previewLayout(.fixed(width: 375, height: 400))
    }
}

let viewController = UIHostingController(rootView: ContentView())
let nav = UINavigationController(rootViewController: viewController)
PlaygroundPage.current.liveView = nav

怎么了？

2022.03.23 添加

我測驗了沒有系結的視圖，它可以作業。我認為該類可以使用其屬性創建一個視圖。但不能通過@Binding。

import SwiftUI
import PlaygroundSupport


struct EditorView: View {
    @Binding var text: String

    var body: some View {
        HStack {
            Text("Name:")
            TextField("Jerry", text: $text)
        }
    }
}

// Just display the name parameter
struct DispView: View {
    let name: String
    var body: some View {
        Text(name)
    }
}

class MyModel: ObservableObject {
    @Published var name: String = "Tom"

    @ViewBuilder
    func editorView() -> some View {
//      EditorView(text: $name) // Error at this line.
        DispView(name: name) // Pass the property.
    }
}

struct ContentView: View {
    @StateObject var model: MyModel = .init()

    var body: some View {
        model.editorView()
    }
}

struct ContentView_Preview: PreviewProvider {
    static var previews: some View {
        ContentView()
            .previewLayout(.fixed(width: 375, height: 400))
    }
}

let viewController = UIHostingController(rootView: ContentView())
let nav = UINavigationController(rootViewController: viewController)
PlaygroundPage.current.liveView = nav

uj5u.com熱心網友回復：

你在錯誤的地方創建了 EditorView，把它放在你的ContentView而不是你的 ViewModel 中。ViewModel 用于保存資料（或模型）而不是 View。我相信 SwiftUI 不是為攜帶視圖而設計的。

struct ContentView: View {
    @StateObject var model: MyModel = .init()

    var body: some View {
        editorView
    }
}

extension ContentView {
    @ViewBuilder
    var editorView: some View {
        EditorView(text: $model.name)
    }
}

如果你仍然想把它放在你的 ViewModel 中，這應該是作業代碼。您可以為視圖初始化程式創建新的系結作為引數。

@ViewBuilder
func editorView() -> some View {
    EditorView(text: 
        Binding { name } set: { newName in self.name = newName }
    )
}

uj5u.com熱心網友回復：

系結由StateObject包裝器（on ObservableObject）提供，并且應該在body（即在視圖層次結構中）創建一個視圖，所以它應該看起來像

struct ContentView: View {
    @StateObject var model: MyModel = .init()

    var body: some View {
        EditorView(text: model.$name)     // << here !!
    }
}

注意：替代方法是直接EditorView依賴于MyModel，然后在這樣的視圖中，您可以創建一個提供所需系結的包裝器。

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