SwiftUI:选择器不会在同一视图中更新文本 [英] SwiftUI: Picker doesn't update text in same view

问题描述

我有一个简单的情况:

struct User: Hashable, Identifiable {
    var id: Int
    var name: String
    
    func hash(into hasher: inout Hasher) {
        hasher.combine(id)
    }
}

let bob = User(id: 1, name: "Bob")
let john = User(id: 2, name: "John")
let users = [bob, john]

struct ParentView: View {    
    @State private var user: User?

    var body: some View {
        VStack(spacing: 0) {
            // Other elements in view...
            Divider()
            ChildPickerView(user: $user)
            Spacer()
        }
    }    
}

struct ChildPickerView: View {
    @Binding var user: User?
    
    var body: some View {
        HStack {
            Text("Selected : \(author?.name ?? "--")")
            Picker(selection: $user, label: Text("Select a user")) {
                ForEach(0..<users.count) {
                    Text(users[$0].name)
                }
            }
        }
        .padding()
    }
}

当我在选择器中选择另一个值时，上面 Text() 中的名称不会更新.但是，当再次点击选择器时，所选用户附近有一个勾号，这意味着该值实际上已被选中.为什么文字没有更新?

When I select another value in the picker, the name in the Text() above isn't updated. However, when tapping the picker again, there is a tick near the selected user, which means the value has actually been selected. Why is the text not updated then?

感谢您的帮助

推荐答案

选择类型和选择器内容 id 或 tag 应该相同.找到以下固定变体.

Type of selection and picker content id or tag should be the same. Find below fixed variant.

使用 Xcode 12.1/iOS 14.1 测试.

Tested with Xcode 12.1 / iOS 14.1.

    VStack {
        Text("Selected : \(user?.name ?? "--")")
        Picker(selection: $user, label: Text("Select a user")) {
            ForEach(users) {
                Text($0.name).tag(Optional($0))
            }
        }
    }

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