使用SwiftUI和Combine进行双向绑定
我正在尝试解决如何在父子关系中的两个ViewModel之间正确传递一个对象或一组值,以便在更新子ViewModel时将更改气泡返回到父视图 当只使用SwiftUI视图并直接绑定到商店时,这非常简单,但我希望将用于字段验证等的业务逻辑与SwiftUI视图分开 下面的代码显示了当父对象更新时,子对象将按预期进行更新,但我需要以某种方式将子对象中更改的值传递回父对象。我对移动应用开发非常陌生,而且还在学习,所以我肯定我错过了一些非常简单的东西使用SwiftUI和Combine进行双向绑定,swiftui,combine,Swiftui,Combine,我正在尝试解决如何在父子关系中的两个ViewModel之间正确传递一个对象或一组值,以便在更新子ViewModel时将更改气泡返回到父视图 当只使用SwiftUI视图并直接绑定到商店时,这非常简单,但我希望将用于字段验证等的业务逻辑与SwiftUI视图分开 下面的代码显示了当父对象更新时,子对象将按预期进行更新,但我需要以某种方式将子对象中更改的值传递回父对象。我对移动应用开发非常陌生,而且还在学习,所以我肯定我错过了一些非常简单的东西 import SwiftUI import Combine
import SwiftUI
import Combine
struct Person: Hashable {
var givenName: String
var familyName: String
}
// my person store - in the real app it's backed by coredata
class PersonStore: ObservableObject {
@Published var people: [Person] = [
Person(
givenName: "Test",
familyName: "Person"
)
]
static let shared = PersonStore()
}
// app entrypoint
struct PersonView: View {
@ObservedObject var viewModel: PersonView_ViewModel = PersonView_ViewModel()
var body: some View {
NavigationView {
VStack {
List(viewModel.people.indices, id: \.self) { idx in
NavigationLink(destination: PersonDetailView(viewModel: PersonDetailView_ViewModel(personIndex: idx))) {
Text(self.viewModel.people[idx].givenName)
}
}
}
}
}
}
class PersonView_ViewModel: ObservableObject {
@Published var people: [Person] = PersonStore.shared.people
}
// this is the detail view
struct PersonDetailView: View {
@ObservedObject var viewModel: PersonDetailView_ViewModel
var body: some View {
Form {
Section(header: Text("Parent View")) {
VStack {
TextField("Given Name", text: self.$viewModel.person.givenName)
Divider()
TextField("Family Name", text: self.$viewModel.person.familyName)
}
}
PersonBasicDetails(viewModel: PersonBasicDetails_ViewModel(person: viewModel.person))
}
}
}
// viewmodel associated with detail view
class PersonDetailView_ViewModel: ObservableObject {
@Published var person: Person
init(personIndex: Int) {
self.person = PersonStore.shared.people[personIndex]
}
}
// this is the child view - in the real app there are multiple sections which are conditionally rendered
struct PersonBasicDetails: View {
@ObservedObject var viewModel: PersonBasicDetails_ViewModel
var body: some View {
Section(header: Text("Child View")) {
VStack {
TextField("Given Name", text: self.$viewModel.person.givenName)
Divider()
TextField("Family Name", text: self.$viewModel.person.familyName)
}
}
}
}
class PersonBasicDetails_ViewModel: ObservableObject {
@Published var person: Person
init(person: Person) {
self.person = person
}
}
struct PersonView_Previews: PreviewProvider {
static var previews: some View {
PersonView()
}
}
在web上的大多数SwiftUI文本字段示例中,绑定是通过使用@State变量来提供的,该变量为您创建绑定实例
但是,也可以使用绑定构造函数创建自定义绑定。下面是一个这样的例子:
TextField(
"Given Name",
text: Binding(
get: { self.$viewModel.person.givenName },
set: { self.$viewModel.person.givenName = $0 }))
如果您想要双向工作,不仅需要发布,还必须使用绑定向上
struct Person: Hashable {
var givenName: String
var familyName: String
}
// my person store - in the real app it's backed by coredata
class PersonStore: ObservableObject {
@Published var people: [Person] = [
Person(givenName: "Test",familyName: "Person")
]
static let shared = PersonStore()
}
// app entrypoint
struct PersonView: View {
@ObservedObject var viewModel: PersonView_ViewModel = PersonView_ViewModel()
var body: some View {
NavigationView {
VStack {
List(viewModel.people.indices, id: \.self) { idx in
NavigationLink(destination: PersonDetailView(viewModel: PersonDetailView_ViewModel(person: self.$viewModel.people , index: idx ))) {
Text(self.viewModel.people[idx].givenName)
}
}
}
}
}
}
class PersonView_ViewModel: ObservableObject {
@Published var people: [Person] = PersonStore.shared.people
}
// this is the detail view
struct PersonDetailView: View {
@ObservedObject var viewModel: PersonDetailView_ViewModel
var body: some View {
Form {
Section(header: Text("Parent View")) {
VStack {
TextField("Given Name", text: self.viewModel.person.givenName)
Divider()
TextField("Family Name", text: self.viewModel.person.familyName)
}
}
PersonBasicDetails(viewModel: PersonBasicDetails_ViewModel(person: viewModel.person))
}
}
}
// viewmodel associated with detail view
class PersonDetailView_ViewModel: ObservableObject {
@Published var person: Binding<Person>
init(person: Binding<[Person]> ,index: Int) {
self.person = person[index]
}
}
// this is the child view - in the real app there are multiple sections which are conditionally rendered
struct PersonBasicDetails: View {
@ObservedObject var viewModel: PersonBasicDetails_ViewModel
var body: some View {
Section(header: Text("Child View")) {
VStack {
TextField("Given Name", text: self.viewModel.person.givenName)
Divider()
TextField("Family Name", text: self.viewModel.person.familyName)
}
}
}
}
class PersonBasicDetails_ViewModel: ObservableObject {
@Published var person: Binding<Person>
init(person: Binding<Person>) {
self.person = person //person
}
}
struct PersonView_Previews: PreviewProvider {
static var previews: some View {
PersonView()
}
}
非常感谢你发布这篇文章。这正是我一直在到处寻找的解决方案!那么,当观察到的值在viewmodel中时,如何使用@state呢?而不是在SwiftUI导入视图类中?