swiftui - SwiftUI ObservedObject 未跨视图更新

Question

我无法让可观察的对象模型工作。

我有两个视图和一个视图模型的简单演示。视图模型是；

import Foundation

class Score: ObservableObject {

    @Published var total = 0

}

一个按钮视图，可将总数加一；

struct ScoreButton: View {
    @ObservedObject var score = Score()

    var body: some View {
        Button(action: {
            score.total += 1
        }, label: {
            Text("Add 1 to Total")
        })
    }
}

然后是一个开始视图来显示结果；

struct OBDemo: View {

    @ObservedObject var result = Score()

    var body: some View {
        VStack {
            ScoreButton()
                .padding()
            Text("Total = \(result.total)")

        }
    }
}

如果我将类、按钮和开始视图放在一个文件中，它就可以工作

Answer 1

您正在创建两个不同的实例Score：

struct ScoreButton: View {
    @ObservedObject var result = Score() // instance #1

struct OBDemo: View {
    @ObservedObject var result = Score() // instance #2

您需要在两个视图中使用相同的实例 - 将 传递@ObservedObject给子视图：

struct OBDemo: View {
    @ObservedObject var result = Score() // create in the parent view

    var body: some View {
        VStack {
            ScoreButton(result: result) // <- pass to the child view
                .padding()
            Text("Total = \(result.total)")

        }
    }
}

struct ScoreButton: View {
    @ObservedObject var score: Score // declare only

    var body: some View {
        Button(action: {
            score.total += 1
        }, label: {
            Text("Add 1 to Total")
        })
    }
}