swift - 如何在数组大小更改后刷新 ForEach 显示元素的数量(SwiftUI、Xcode 11 Beta 5)

import SwiftUI
 
struct test : View {
    @State var array:[String] = []
    @State var label = "not pressed"
    var body: some View {
        VStack{
            Text(label).onTapGesture {
                self.array.append("ForEach refreshed")
                self.label = "pressed"
            }
            ForEach(0..<array.count){number in
                Text(self.array[number])
            }
        }
}
}
 
#if DEBUG
struct test_Previews: PreviewProvider {
    static var previews: some View {
        test()
    }
}
#endif

import SwiftUI
 
struct ContentView : View {
    @State var array:[String] = []
    @State var label = "not pressed"
    var body: some View {
        VStack{
            Text(label).onTapGesture {
                self.array.append("ForEach refreshed")
                self.label = "pressed"
            }
            ForEach(array, id: \.self) { item in
                Text(item)
            }
        }
    }
}

struct ContentView : View {
    @State var array:[String] = []
    @State var label = "not pressed"
    var body: some View {
        VStack{
            Text(label).onTapGesture {
                self.array.append("ForEach refreshed")
                self.label = "pressed"
            }
            ForEach(array.indices, id: \.self) { index in
                Text(self.array[index])
            }
        }
    }
}

具有非恒定范围视图刷新的Swift ForEach

swift view swiftui-foreach

我知道这是一个简单的问题，但我还没有找到答案。我想了解基本概念。

我试图用非常量范围更新ForEach，closing参数是分配给按钮的变量。

变量被赋予@状态，因此应该刷新视图。不知怎么的，它不起作用了。

 
 
import SwiftUI
 
struct ContentView: View {
    @State private var numberOfTimes = 5
    let timesPicker = [2,5,10,12,20]
    @State private var tableToPractice = 2
    enum answerState {
        case unanswered
        case wrong
        case right
    }
    func listRange(){
        
    }
    
    var body: some View {
        NavigationView{
            HStack{
                VStack{
                    Form{
                        Section {
                            Picker("Tip percentage", selection: $numberOfTimes) {
                                ForEach(timesPicker, id: \.self) {
                                    Text($0, format: .number)
                                }
                            }
                            .pickerStyle(.segmented)
                        } header: {
                            Text("How many times do you want to practice?")
                        }
                        Section{
                            Stepper("Table to practice: \(tableToPractice.formatted())", value: $tableToPractice, in: 2...16 )
                        }
                            Button("Start Now", action: listRange).buttonStyle(.bordered)
                        
 
                        
                        List{
                            ForEach(0..<numberOfTimes){
                                Text("Dynamic row \($0)")
                            }
                        }
                    }.foregroundColor(.gray)
                }
            }
        }
    }
}
 
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}
 

 发布于 1 年前

✅ 最佳回答：

问题是没有确定范围。让我们排几行

    struct Row: Identifiable {
        let id = UUID()
    }

然后设置一组可识别的项目

    @State private var numberOfTimes = 5
    @State private var rows = Array(repeating: Row(), count: 5)

现在，您可以获得响应列表

    List{
        ForEach(rows) { row in
            Text("Dynamic row")
        }
    }

调用更改时更新以重新创建阵列

    .onChange(of: numberOfTimes) { newValue in
        rows = Array(repeating: Row(), count: newValue)
        numberOfTimes = newValue
    }

应在表单上调用onChange。

当您能够更好地查看模型数据时，这将更有意义，有关更深入的示例，请参阅apple文档。

这是针对lazy v stack的，但我考虑的是数据模型设置

https://developer.apple.com/documentation/swiftui/grouping-data-with-lazy-stack-views

最终解决办法：将FOREACH的列表改为@Published属性即可。