從SwiftUI中的結構陣列更新@StatevarDouble-有解無憂

我整天都在看 StackOverFlow（和 Internet）以使這個按鈕起作用，但我沒有找到任何東西。

如您所見，我想通過使用最簡單的解決方案來更改單擊按鈕時的值。

以下是代碼：

// Element.swift

import Foundation
import SwiftUI

struct Element: Identifiable {
    let id = UUID()
    @State var value: Double
    let title: String
}

let elements = [
    Element(value: 10, title: "This is a title"),
    Element(value: 100, title: "This is another title")
]

// ElementView.swift

import SwiftUI

struct ElementView: View {

    let element: Element

    var body: some View {
        HStack {
            Text(element.title)
            Text("\(element.value)")
            Button("More", action: { element.value  = 10 })
        }
    }

}

struct ElementView_Previews: PreviewProvider {
    static var previews: some View {
        ElementView(element: elements[0])
    }
}

// ContentView.swift

import SwiftUI

struct ContentView: View {

    var body: some View {
        VStack {
            ForEach(elements) { element in
                ElementView(element: element)
            }
        }
    }

}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

令人驚訝的是，我對 Xcode 沒有任何問題。

我錯過了什么？提前致謝！:P

uj5u.com熱心網友回復：

你有幾個關于你如何對待狀態的問題。通常，在 SwiftUI 中，狀態由父級持有并通過 Binding 傳遞給子級。@State用于內部而不是模型內部也非常重要View。

有關更改和解釋，請參閱行內注釋。

struct Element: Identifiable {
    let id = UUID()
    var value: Double //Remove @State here -- @State is for use in a View
    let title: String
}

struct ElementView: View {

    @Binding var element: Element //pass Element via Binding so it is mutable

    var body: some View {
        HStack {
            Text(element.title)
            Text("\(element.value)")
            Button("More", action: { element.value  = 10 })
        }
    }

}

struct ElementView_Previews: PreviewProvider {
    static var previews: some View {
        ElementView(element: .constant(Element(value: 10, title: "This is a title"))) //use .constant() for a Binding in a Preview
    }
}

struct ContentView: View {
    @State private var elements = [ //define elements with @State so they are mutable
        Element(value: 10, title: "This is a title"),
        Element(value: 100, title: "This is another title")
    ]
    
    var body: some View {
        VStack {
            ForEach($elements) { $element in //use element binding syntax to get a binding to each item in the array
                ElementView(element: $element)
            }
        }
    }

}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

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