当 SwiftUI Picker 选择更改时，有没有办法调用函数? [英] Is there a way to call a function when a SwiftUI Picker selection changes?

问题描述

我想在 selectedOption 的值发生变化时调用一个函数.有没有办法在 SwiftUI 中执行此操作，类似于在编辑 TextField 时执行此操作?

I would like to call a function when selectedOption's value changes. Is there a way to do this in SwiftUI similar to when editing a TextField?

具体来说，我想在用户更改 selectedOption 时保存所选选项.

Specifically, I would like to save the selected option when the user changes the selectedOption.

这是我的选择器:

struct BuilderPicker: View {
    let name: String
    let options: Array<String>
    @State var selectedOption = 0
    var body: some View {
        HStack {
            Text(name)
                .font(.body)
                .padding(.leading, 10)
            Picker(selection: $selectedOption, label: Text(name)) {
                ForEach(0 ..< options.count) {
                    Text(self.options[$0]).tag($0)
                }
            }.pickerStyle(SegmentedPickerStyle())
                .padding(.trailing, 25)
        }.onTapGesture {
            self.selectedOption = self.selectedOption == 0 ? 1 : 0
        }
            .padding(.init(top: 10, leading: 10, bottom: 10, trailing: 0))
            .border(Color.secondary, width: 3)
            .padding(.init(top: 0, leading: 15, bottom: 0, trailing: 15))
            .font(.body)
    }

}

我还是 SwiftUI 的新手，希望得到一些帮助.谢谢！

I’m still new to SwiftUI and would love some help. Thanks!

推荐答案

如果 @State 值将用于视图中，则不需要额外的变量 name

If the @State value will be used in a View, you don't need extra variable name

  struct BuilderPicker: View {
// let name: String = ""
 let options: Array<String> = ["1", "2","3","4","5"]
 @State var selectedOption = 0
 var body: some View {
    HStack {
        Text(options[selectedOption])
            .font(.body)
            .padding(.leading, 10)
        Picker(selection: $selectedOption, label:    Text(options[selectedOption])) {
            ForEach(0 ..< options.count) {
                Text(self.options[$0]).tag($0)
            }
        }.pickerStyle(SegmentedPickerStyle())
            .padding(.trailing, 25)}
//        }.onTapGesture {
//            self.selectedOption = self.selectedOption == 0 ? 1 : 0
//        }
        .padding(.init(top: 10, leading: 10, bottom: 10, trailing: 0))
        .border(Color.secondary, width: 3)
        .padding(.init(top: 0, leading: 15, bottom: 0, trailing: 15))
        .font(.body)
    }


 }

如果需要对@State 进行分离操作，最简单的方法是在视图中添加一行:onReceive().

If you need separated operation on the @State, the simplest way is adding one line : onReceive() to the view.

  HStack {
        Text("")
            .font(.body)
            .padding(.leading, 10)
        Picker(selection: $selectedOption, label: Text("")) {
            ForEach(0 ..< options.count) {
                Text(self.options[$0]).tag($0)
            }
        }.pickerStyle(SegmentedPickerStyle())
            .padding(.trailing, 25)}
  //        }.onTapGesture {
 //            self.selectedOption = self.selectedOption == 0 ? 1 : 0
 //        }
        .padding(.init(top: 10, leading: 10, bottom: 10, trailing: 0))
        .border(Color.secondary, width: 3)
        .padding(.init(top: 0, leading: 15, bottom: 0, trailing: 15))
        .font(.body)
        .onReceive([self.selectedOption].publisher.first()) { (value) in
            print(value)
    }

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