在SwiftUI中用文本字段更新字符串的困难

Question

我当前在使用TextField修改String值时遇到问题。到目前为止，这是我的(简化(代码：

class GradeItem: ObservableObject {
@Published var name: String
@Published var scoredPoints: Double
@Published var totalPoints: Double
let isUserCreated: Bool
init(name: String, scoredPoints: Double, totalPoints: Double, isUserCreated: Bool) {
self.name = name
self.scoredPoints = scoredPoints
self.totalPoints = totalPoints
self.isUserCreated = isUserCreated
}
}
var courses: [Course] {
// initialization code...
}
struct GradeCalculatorView: View {
@State var selectedCourseIndex: Int = 0
var body: some View {
VStack {
// allows user to select a course:
ForEach(0 ..< courses.count) { i in
Button(action: {
self.selectedCourseIndex = i
}, label: {
Text(courses[i].name)
})
}
CourseView(course: courses[selectedCourseIndex])
}
}
}
struct CourseView: View {
@ObservedObject var course: Course   // passed in from GradeCalculatorView
var body: some View {
VStack(alignment: .leading) {
Text(course.name)
ForEach(course.categories, id: .name) { category in
GradeCategoryView(category: category)
}
}.padding(.leading).frame(alignment: .leading)
}
}
struct GradeCategoryView: View {
@ObservedObject var category: GradeCategory   // passed in from CourseView
var body: some View {
VStack(alignment: HorizontalAlignment.leading) {
HStack {
Text(category.name)
Spacer()
}
ForEach(category.items, id:.name) { item in
GradeItemRow(item: item)
}
}
}
}
struct GradeItemRow: View {
@ObservedObject var item: GradeItem   // passed in from GradeCategoryView
var body: some View {
TextField("Item Name", text: $item.name)
}
}

我似乎无法使用TextField修改GradeItem对象的名称。编辑TextField时，其文本会临时更改。但是，当重新加载GradeItemRow视图时，它会显示GradeItem对象的原始名称，而不是更新后的名称。

有人能帮忙吗？

提前感谢

更新：根据您的请求，我为这个示例代码添加了更多上下文。

我知道这是行不通的，因为当我试图用TextField修改GradeItem的名称时，它会临时更改。但是，当我选择一个不同的课程，然后选择我最初参加的课程时，TextField会显示未修改的名称值。

Answer 1

以下测试有效。

class GradeItem: ObservableObject {

@Published var name: String
@Published var scoredPoints: Double
@Published var totalPoints: Double
let isUserCreated: Bool

init(name: String, scoredPoints: Double, totalPoints: Double, isUserCreated: Bool) {
self.name = name
self.scoredPoints = scoredPoints
self.totalPoints = totalPoints
self.isUserCreated = isUserCreated
}

init() {
self.name = "gradeItem" + UUID().uuidString
self.scoredPoints = 0.0
self.totalPoints = 0.0
self.isUserCreated = false
}
}
class Course: ObservableObject {
@Published var name: String
@Published var categories: [GradeCategory]
init(name: String, categories: [GradeCategory]) {
self.name = name
self.categories = categories
}
init() {
self.name = "course_" + UUID().uuidString
self.categories = [GradeCategory]()
self.categories.append(GradeCategory())
}
}
class GradeCategory: ObservableObject {
@Published var name: String
@Published var items: [GradeItem]
init(name: String, items: [GradeItem]) {
self.name = name
self.items = items
}
init() {
self.name = "category_" + UUID().uuidString
self.items = [GradeItem]()
self.items.append(GradeItem())
}
}
struct GradeItemRow: View {
@ObservedObject var item: GradeItem   // passed in from GradeCategoryView

var body: some View {
TextField("Item Name", text: $item.name).textFieldStyle(RoundedBorderTextFieldStyle())
}
}
struct GradeCategoryView: View {
@ObservedObject var category: GradeCategory   // passed in from CourseView

var body: some View {
VStack(alignment: .leading) {
HStack {
Text(category.name)
Spacer()
}
ForEach(category.items, id: .name) { item in
GradeItemRow(item: item)
}
}
}
}
struct CourseView: View {
@Environment(.presentationMode) var presentationMode: Binding<PresentationMode>
@ObservedObject var course: Course   // passed in from ContentView

var body: some View {
VStack(alignment: .leading) {
Button(action: {
self.presentationMode.wrappedValue.dismiss()
}, label: {
Text("done")
})
Spacer()
Text(course.name)
ForEach(course.categories, id: .name) { category in
GradeCategoryView(category: category)
}
Spacer()
}.padding(.leading).frame(alignment: .leading)
}
}
struct ContentView: View {
@State var courses: [Course] = [Course(), Course()]
@State var selectedCourseIndex: Int = 0
@State var showCourse = false

var body: some View {
VStack {
ForEach(0 ..< courses.count) { i in
Button(action: {
self.selectedCourseIndex = i
self.showCourse = true
}, label: {
Text(self.courses[i].name)
})
}
}.sheet(isPresented: self.$showCourse) {
CourseView(course: self.courses[self.selectedCourseIndex])
}
}
}