SwiftUI:选择器中的 ForEach 未更新 [英] SwiftUI: ForEach in Picker doesn't update

问题描述

我有一个元素数组，我想使用 Picker 从中选择一个元素，我有一个 Button，它只是向数组添加一个新元素.问题是，当我添加一个元素时，Picker 选项不会更新.它不适用于 DefaultPickerStyle，但适用于 SegmentedPickerStyle.

I have an array of elements, from which I want to chose one using Picker, and I have a Button which simply adds a new element to the array. The thing is, when I add an element, the Picker choices are not updated. It doesn't work with DefaultPickerStyle, but works with SegmentedPickerStyle.

代码:

import SwiftUI

struct ExampleView: View {
    @State
    var array : Array<Int> = [Int]()
    @State
    var selection : Int = 0

    var body: some View {
        VStack {
            Picker("", selection: self.$selection) {
                ForEach(self.array, id : \.self) { i in
                    Text(String(i))
                }
            }
            // uncomment, and picker will refresh upon pushing the button
            //.pickerStyle(SegmentedPickerStyle())

            Button(action: {
                self.array.append(self.array.count)
            }){
                Text("Add me: " + String(self.array.count))
            }
        }
    }
}

struct ExampleView_Previews: PreviewProvider {
    static var previews: some View {
        ExampleView()
    }
}

有什么办法可以解决这个问题吗?我真的需要更新 Picker(以其默认样式).Xcode 版本 11.2.1 (11B500).

Is there any way to fix this? I really need to update the Picker (in its default styling). Xcode Version 11.2.1 (11B500).

推荐答案

正如@e-coms 所指出的，有一个 类似问题.@p-ent (github) 是在每次按下按钮时为 Picker 重新分配一个唯一的 .id(...)，以强制更新.适应我的问题:

As @e-coms pointed out, there is a similar question. An acceptable workaround found by @p-ent (github) is to re-assign a unique .id(...) for Picker on each button push, to force its update. Adapted to my question:

UPD:更好，谢谢@e-coms

UPD: even better, thanks @e-coms

import SwiftUI

struct ExampleView: View {
    @State
    var array : Array<Int> = [0,1,2]
    @State
    var selection : Int = 0

    var body: some View {
        VStack {
            Picker("", selection: self.$selection) {
                ForEach(self.array, id : \.self) { i in
                    Text(String(i))
                }
            }
            .id(self.array)

            Button(action: {
                self.array.append(self.array.count)
            }){
                Text("Add me: " + String(self.array.count))
            }
        }
    }
}

struct ExampleView_Previews: PreviewProvider {
    static var previews: some View {
        ExampleView()
    }
}

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