ios - Swift Array .append() 方法在 SwiftUI 中不起作用

Question

我正在努力在 SwiftUI 中做一个简单的追加。这是我的代码:

// This is defined in my custom view
var newClass = Class()

// This is inside a List container (I hid the Button's content because it doesn't matter)
Button(action: {
    self.newClass.students.append(Student())
    print(self.newClass.students) // This prints an Array with only one Student() instance - the one defined in the struct's init
})

// These are the custom structs used
struct Class: Identifiable {
    var id = UUID()
    @State var name = ""
    @State var students: [Student] = [Student()] // Right here
}

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

我认为它可能与新的 @Struct 有某种关系。事情，但我是iOS(和Swift)开发的新手，所以我不确定。

Answer 1

让我们稍微修改一下模型...

struct Class: Identifiable {
    var id = UUID()
    var name = ""
    var students: [Student] = [Student()]
}

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

... 而不是使用 @State在不想要的地方(因为它被设计在 View 内部，而不是模型)，让我们引入 View Model 层作为

class ClassViewModel: ObservableObject {
    @Published var newClass = Class()
}

现在我们可以声明行为符合预期的相关 View

struct ClassView: View {
    @ObservedObject var vm = ClassViewModel()

    var body: some View {
        Button("Add Student") {
            self.vm.newClass.students.append(Student())
            print(self.vm.newClass.students)
        }
    }
}

输出:

Test[4298:344875] [Agent] Received display message [Test.Student(id: D1410829-F039-4D15-8440-69DEF0D55A26, name: ""), Test.Student(id: 50D45CC7-8144-49CC-88BE-598C890F2D4D, name: "")]