父 NavigationView 的 SwiftUI 更新数据

Question

如何更新位于 NavigationView 细节中的 TextField 中的数据？我希望在父视图的列表中更新数据。这是我的代码：

class Address: ObservableObject, Identifiable {
    let id = UUID()
    @Published var name: String
    @Published var age: String
    
    init(name: String, age: String) {
        self.name = name
        self.age = age
    }
}
class AddressBook: ObservableObject {
    @Published var addresses: [Address]

    init(addresses: [Address]) {
        self.addresses = addresses
    }
}
struct TestData {
    static let addressbook = AddressBook(addresses: [
        Address(name: "Person1", age: "39"),
        Address(name: "Person2", age: "22")
    ])
}
struct ContentView: View {
    @ObservedObject var addressbook = TestData.addressbook
    
    var body: some View {
        NavigationView {
            List (addressbook.addresses) {address in
                NavigationLink(destination: AddressDetail(address: address)) {
                    Text(address.name)
                }
            }
            .navigationBarTitle("Addressbook")
        }
        
    }
}

struct AddressDetail: View {
    @ObservedObject var address: Address
    
    var body: some View {
        Form {
            TextField("name", text: $address.name)
            
            TextField("age", text: $address.age)
        }
        
    }
}

此代码不起作用：如果我转到 AddressDetail-View，更改 TextField 值然后返回，则更改不会在 List-View 中更新。

妮可

Answer 1

问题在于Address 是一个类，因此如果其发布的属性发生更改，addresses 中的引用不会更改，但ContentView 视图将addressbook 视为地址容器。

这里是可能方法的演示（经过测试并适用于 Xcode 12b / iOS 14，也在 11.4 / iOS 13.4 上）

List (addressbook.addresses) {address in
    NavigationLink(destination: AddressDetail(address: address)) {
        Text(address.name)
            .onReceive(address.objectWillChange) { _ in
                self.addressbook.objectWillChange.send()
            }
    }
}

替代方案：基于Binding（需要更多更改，所以对我而言，不太可取，但值得一提

struct Address: Identifiable, Hashable {
    let id = UUID()
    var name: String
    var age: String

    init(name: String, age: String) {
        self.name = name
        self.age = age
    }
}
class AddressBook: ObservableObject {
    @Published var addresses: [Address]

    init(addresses: [Address]) {
        self.addresses = addresses
    }
}
struct TestData {
    static let addressbook = AddressBook(addresses: [
        Address(name: "Person1", age: "39"),
        Address(name: "Person2", age: "22")
    ])
}

struct ContentView: View {
    @ObservedObject var addressbook = TestData.addressbook

    var body: some View {
        NavigationView {
            List (Array(addressbook.addresses.enumerated()), id: \.element) { i, address in
                NavigationLink(destination: AddressDetail(address: self.$addressbook.addresses[i])) {
                    Text(address.name)
                }
            }
            .navigationBarTitle("Addressbook")
        }

    }
}

struct AddressDetail: View {
    @Binding var address: Address

    @State private var name: String
    @State private var age: String

    init(address: Binding<Address>) {
        _address = address
        _name = State(initialValue: _address.wrappedValue.name)
        _age = State(initialValue: _address.wrappedValue.age)
    }
    var body: some View {
        Form {
            TextField("name", text: $name)

            TextField("age", text: $age)
        }
        .onDisappear {
            self.address.name = self.name
            self.address.age = self.age
        }
    }
}