SwiftUI ObservedObject没有跨视图更新

Question

我不能让可观察到的对象模型工作。

我有一个两个视图的简单演示和一个视图模型。视图模型为；

import Foundation

class Score: ObservableObject {

    @Published var total = 0

}

按钮视图，将其添加到总数中；

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

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

然后用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、按钮和启动视图放在一个文件中，它就能工作。

Answer 1

您正在创建两个不同的Score实例

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@ObservedObject传递给子视图：

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")
        })
    }
}