如何解决从 CoreData 中删除数据
我想马上说我是 Swift 的新手。我的任务是通过单击按钮删除某些数据 附言单击按钮并删除“框架”,如何为此重写函数 (在 SwiftUI、AppDelegate 中工作)
//MARK: - PROPERTIES
@FetchRequest(entity: TodoDB.entity(),sortDescriptors: [NSSortDescriptor(keyPath: \TodoDB.name,ascending: true)]) var manyTasksTodo: FetchedResults<TodoDB>
//MARK: - FUNCTION
public func deletetodo(at offsets: IndexSet){
for index in offsets{
let todoDB = manyTasksTodo[index]
managedobjectContext.delete(todoDB)
do{
try managedobjectContext.save()
} catch{
print(error)
}
}
}
完整代码:
import SwiftUI
struct ContentView: View {
//MARK: - PROPERTIES
@Environment(\.managedobjectContext) var managedobjectContext
@FetchRequest(entity: TodoDB.entity(),ascending: true)]) var manyTasksTodo: FetchedResults<TodoDB>
@State public var AddTodo: Bool = false
@State private var animationButton: Bool = false
@Namespace var animationID
//MARK: - BODY
var body: some View {
ScrollView(.vertical,showsIndicators: false){
vstack{
ForEach(self.manyTasksTodo,id: \.self) { (todoDB: TodoDB) in
vstack(alignment: .leading,spacing: 5){
ZStack{
Button(action: {
},label: {
Image(systemName: "trash")
.frame(maxWidth: .infinity,alignment: .bottomTrailing)
.padding(.bottom,30)
.foregroundColor(.black)
})
Divider()
Text(todoDB.attribute ?? "unkNown attribute")
.foregroundColor(.black)
.font(.callout)
.padding(.bottom,30)
}
Text(todoDB.name ?? "unkNown task")
.foregroundColor(.black)
.padding(.bottom)
Text(todoDB.date ?? Date(),style: .date)
.foregroundColor(.black)
.font(.callout)
HStack{
Spacer()
}
}//vstack
.padding()
.background(Color("Red"))
.cornerRadius(10)
.padding()
}//: FOREACH
.onDelete(perform: deletetodo(at:))
Spacer()
}
.shadow(color: Color.black.opacity(0.3),radius: 10,x: 0,y: 10)
.shadow(color: Color.black.opacity(0.2),radius: 5,y: 2)
}
.padding(.top,45)
.background(Color("Bg"))
.edgesIgnoringSafeArea(.all)
.overlay(
ZStack{
Group{
Circle()
.fill(Color.black)
.opacity(self.animationButton ? 0.2 : 0)
.scaleEffect(self.animationButton ? 1 : 0)
.frame(width: 68,height: 68,alignment: .center)
Circle()
.fill(Color.black)
.opacity(self.animationButton ? 0.15 : 0)
.scaleEffect(self.animationButton ? 1 : 0)
.frame(width: 88,height: 88,alignment: .center)
}
.animation(Animation.easeInOut(duration: 2).repeatForever(autoreverses: true),value: self.animationButton)
Button(action: {
self.AddTodo.toggle()
},label: {
Image(systemName: "plus.circle.fill")
.resizable()
.scaledToFit()
.background(Circle().fill(Color.white))
.foregroundColor(Color.black)
.frame(width: 48,height: 48,alignment: .center)
})
.sheet(isPresented: $AddTodo){
AddTodoView().environment(\.managedobjectContext,self.managedobjectContext)}
.onAppear(perform: {
self.animationButton.toggle()
})
}//: ZSTACK
.padding(.bottom,15)
.padding(.trailing,15),alignment: .bottomTrailing
)
//}//: NAVIGATON
}
//MARK: - FUNCTION
public func deletetodo(at offsets: IndexSet){
for index in offsets{
let todoDB = manyTasksTodo[index]
managedobjectContext.delete(todoDB)
do{
try managedobjectContext.save()
} catch{
print(error)
}
}
}
}
//MARK: - PREIVIEW
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
return ContentView()
.environment(\.managedobjectContext,context)
}
}
解决方法
当您将 IndexSet
与 onDelete
循环一起使用时,ForEach
方法有效。
由于您无权使用 IndexSet
访问 Button
,因此您传递了实际项目。
将您的功能更改为此。
public func deleteTodo(todoDB: TodoDB){
managedObjectContext.delete(todoDB)
do{
try managedObjectContext.save()
} catch{
print(error)
}
}
然后将此代码放入垃圾箱按钮的操作中,如下所示。
deleteTodo(todoDB: todoDB)
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