ios - SwiftUI 中的 ForEach TextField

Question

假设我有一个类 Student

class Student: Identifiable, ObservableObject {
    var id = UUID()

    @Published var name = ""
}

在另一个类(称为 Class)的数组中使用

class Class: Identifiable, ObservableObject {
    var id = UUID()

    @Published var name = ""
    var students = [Student()]
}

在我的 View 中是这样定义的。

@ObservedObject var newClass = Class()

我的问题是:如何为每个 Student 创建一个 TextField 并将其与 name 属性正确绑定(bind)(不出错) ？

ForEach(self.newClass.students) { student in
    TextField("Name", text: student.name)
}

现在，Xcode 向我抛出这个:

Cannot convert value of type 'TextField<Text>' to closure result type '_'

我试过在调用变量之前添加一些$，但似乎没有用。

Answer 1

只需将学生姓名属性的 @Published 更改为 @State。 @State 是为您提供带有 $ 前缀的 Binding。

import SwiftUI

class Student: Identifiable, ObservableObject {
  var id = UUID()

  @State var name = ""
}

class Class: Identifiable, ObservableObject {
  var id = UUID()

  @Published var name = ""
  var students = [Student()]
}

struct ContentView: View {
  @ObservedObject var newClass = Class()

  var body: some View {
    Form {
      ForEach(self.newClass.students) { student in
        TextField("Name", text: student.$name) // note the $name here
      }
    }
  }
}

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
    ContentView()
  }
}

一般来说，我还建议使用结构而不是类。

struct Student: Identifiable {
  var id = UUID()
  @State var name = ""
}

struct Class: Identifiable {
  var id = UUID()

  var name = ""
  var students = [
    Student(name: "Yo"),
    Student(name: "Ya"),
  ]
}

struct ContentView: View {
  @State private var newClass = Class()

  var body: some View {
    Form {
      ForEach(self.newClass.students) { student in
        TextField("Name", text: student.$name)
      }
    }
  }
}