swift - 如何通过带有 FetchedResults 和 CoreData 的导航链接传递数据？
问题描述
我正在尝试通过 ScrollView 中的导航链接将 FetchResult 数据从一个屏幕传递到另一个屏幕。
当我尝试在 DetailView 屏幕中调用传递的数据时，出现以下错误：
Instance member "" cannoth be used on type "SavedPoem"
下面的代码 - 保存的诗歌列表
import SwiftUI
struct SavedPoemList: View {
@Environment(\.managedObjectContext) var moc
@FetchRequest(entity: SavedPoem.entity(), sortDescriptors: []) var savedpoems : FetchedResults<SavedPoem>
var body: some View {
VStack (alignment: .leading, spacing: 0) {
HStack{
Text("Your Saved Poems")
.font(.title)
.fontWeight(.black)
.foregroundColor(.black)
Spacer()
}.padding(.bottom)
.padding(.trailing)
.padding(.leading)
ScrollView {
ForEach(savedpoems, id:\.title) {SavedPoem in
NavigationLink (destination: DetailViewSaved()){
ZStack {
Rectangle()
.fill(Color.white)
.frame(width: UIScreen.screenWidth - 40, height: 70)
.cornerRadius(5)
.padding([.horizontal], 20)
// .shadow(color: .gray, radius: 10)
HStack {
VStack (alignment: .leading){
Text("\(SavedPoem.title ?? "")")
.font(.headline)
.foregroundColor(.black)
.lineLimit(1)
.padding(.bottom, 3)
Text("\(SavedPoem.author ?? "")")
.font(.subheadline)
.foregroundColor(.secondary)
}
.padding(.trailing)
Spacer()
}
.padding()
}.padding(.bottom,10)
}
}.onDelete(perform: self.remove)
}
.navigationTitle("My Saved Poems")
.navigationBarHidden(true)
.edgesIgnoringSafeArea(.top)
.padding(.bottom, 30)
}
.padding(.horizontal, 30)
.edgesIgnoringSafeArea(.bottom)
}
func remove(at offsets : IndexSet) {
for index in offsets {
let delete = savedpoems[index]
self.moc.delete(delete)
}
try? self.moc.save()
}
}
和详细视图的代码
import SwiftUI
struct DetailViewSaved: View {
@ObservedObject var fetch = FetchPoem()
@Environment(\.managedObjectContext) var moc
@FetchRequest(entity: SavedPoem.entity(), sortDescriptors: []) var savedpoems : FetchedResults<SavedPoem>
@State private var saved : Bool = false
var currentDate = Text(Date().addingTimeInterval(600), style: .date)
var body: some View {
VStack {
HStack{
// NavigationLink( destination: HomeView())
// {
//
// Image(systemName: "arrow.backward")
// .font(.system(size: 25, weight: .heavy))
// .foregroundColor(.black)
// }
Spacer(minLength: 0)
Button(action:
{
// self.moc.delete(delete)
try? self.moc.save()
}) {
Image(systemName: saved ? "bookmark.fill": "bookmark")
.font(.system(size: 25, weight: .heavy))
.foregroundColor(.black)
}
}
ScrollView {
VStack {
HStack{
VStack (alignment: .leading) {
Text("Today's Poem, \(currentDate)")
.font(.subheadline)
.foregroundColor(Color.gray)
.padding(.bottom, 20)
.padding(.top, 10)
Text("\(SavedPoem.title ?? "")")
// .font(.largeTitle)
// .fontWeight(.heavy)
// .foregroundColor(.black)
// .padding(.bottom, 20)
// .lineSpacing(0)
// Text("BY "+poem.author.uppercased())
Text("BY \(SavedPoem.author ?? "")")
// .font(.subheadline)
// .foregroundColor(Color.gray)
// .padding(.bottom, 20)
HStack {
Text("\(SavedPoem.lines ?? "")")
// .font(.body)
// .foregroundColor(.black)
// .padding(.bottom)
// .lineSpacing(5)
//
Spacer()
}
Spacer()
}
.padding()
}
}
}
}
}
}
我错过了什么吗？如何解决此问题，并将列表视图中 Fetchedresults 中的数据传递到详细屏幕？
提前致谢。
编辑回复代码
已保存的诗歌列表：
import SwiftUI
struct SavedPoemList: View {
@Environment(\.managedObjectContext) var moc
@FetchRequest(entity: SavedPoem.entity(), sortDescriptors: []) var savedpoems : FetchedResults<SavedPoem>
var body: some View {
VStack (alignment: .leading, spacing: 0) {
HStack{
Text("Your Saved Poems")
.font(.title)
.fontWeight(.black)
.foregroundColor(.black)
Spacer()
Text("Edit")
.font(.subheadline)
.fontWeight(.black)
.foregroundColor(.gray)
}.padding(.bottom)
.padding(.trailing)
.padding(.leading)
ScrollView {
ForEach(savedpoems, id:\.title) {SavedPoem in
NavigationLink (destination: DetailViewSaved(savedPoem: SavedPoem)){
ZStack {
Rectangle()
.fill(Color.white)
.frame(width: UIScreen.screenWidth - 40, height: 70)
.cornerRadius(5)
.padding([.horizontal], 20)
// .shadow(color: .gray, radius: 10)
HStack {
VStack (alignment: .leading){
Text("\(SavedPoem.title ?? "")")
.font(.headline)
.foregroundColor(.black)
.lineLimit(1)
.padding(.bottom, 3)
Text("\(SavedPoem.author ?? "")")
.font(.subheadline)
.foregroundColor(.secondary)
}
.padding(.trailing)
Spacer()
}
.padding()
}.padding(.bottom,10)
}
}.onDelete(perform: self.remove)
}
.navigationTitle("My Saved Poems")
.navigationBarHidden(true)
.edgesIgnoringSafeArea(.top)
.padding(.bottom, 30)
}
.padding(.horizontal, 30)
.edgesIgnoringSafeArea(.bottom)
}
func remove(at offsets : IndexSet) {
for index in offsets {
let delete = savedpoems[index]
self.moc.delete(delete)
}
try? self.moc.save()
}
}
详细视图
import SwiftUI
struct DetailViewSaved: View {
@ObservedObject var fetch = FetchPoem()
@Environment(\.managedObjectContext) var moc
@FetchRequest(entity: SavedPoem.entity(), sortDescriptors: []) var savedpoems : FetchedResults<SavedPoem>
@State private var saved : Bool = false
var savedPoem : SavedPoem
var currentDate = Text(Date().addingTimeInterval(600), style: .date)
var body: some View {
VStack {
HStack{
// NavigationLink( destination: HomeView())
// {
//
// Image(systemName: "arrow.backward")
// .font(.system(size: 25, weight: .heavy))
// .foregroundColor(.black)
// }
Spacer(minLength: 0)
Button(action:
{
// self.moc.delete(delete)
try? self.moc.save()
}) {
Image(systemName: saved ? "bookmark.fill": "bookmark")
.font(.system(size: 25, weight: .heavy))
.foregroundColor(.black)
}
}
ScrollView {
VStack {
HStack{
VStack (alignment: .leading) {
// Text("Today's Poem, \(currentDate)")
// .font(.subheadline)
// .foregroundColor(Color.gray)
// .padding(.bottom, 20)
// .padding(.top, 10)
Text("\(savedPoem.title ?? "")")
// .font(.largeTitle)
// .fontWeight(.heavy)
// .foregroundColor(.black)
// .padding(.bottom, 20)
// .lineSpacing(0)
// Text("BY "+poem.author.uppercased())
// Text("BY \(SavedPoem.author ?? "")")
// .font(.subheadline)
// .foregroundColor(Color.gray)
// .padding(.bottom, 20)
// HStack {
// Text("\(SavedPoem.lines ?? "")")
// .font(.body)
// .foregroundColor(.black)
// .padding(.bottom)
// .lineSpacing(5)
//
Spacer()
}
Spacer()
}
.padding()
}
}
}
}
}
}
struct DetailViewSaved_Previews: PreviewProvider {
static var previews: some View {
DetailViewSaved(savedPoem: SavedPoem)
}
}
解决方案
我用你的例子做了一个例子：
SavedPoemList：将一个项目从您的数组传递给您Detail View，就像这样：
NavigationLink (destination: DetailViewSaved(savedPoem: SavedPoem)){
VStack{
Text("Your row view")
}
}
并在您的Detail View：
struct DetailViewSaved: View {
var savedPoem : SavedPoem
var body: some View {
Text("Your view")
}
}
推荐阅读
- php - Laravel 5.8 Auth::guard()->check() 总是返回 false
- ios - 如何在没有 StoryBoards 的情况下以编程方式从 viewcontroller 转换到 TabbarController？
- python - 我对 Bellman-Ford 算法正确性的实现是错误的吗？
- ssis - SSIS 未将所有行从 ODBC（oracle）插入 SQL Server 2019
- reactjs - 如何在 React 中将 fontColor、fontBackgroundColor、fontSize 添加到 ckeditor5
- python - 如何在循环中从列表中删除值？pythoncrash课程书中的问题
- spartacus-storefront - 当具有无定价角色的用户登录“您无权执行此操作”时如何修复。在登陆页面中
- ui5-webcomponents - 标签容器渲染问题
- arrays - 套接字序列化错误，需要一个类似字节的对象，而不是 'str'
- database - 如何在 MongoDB 中获取到周末的日期？