问题描述
您可以尝试以下操作,它应适合您的情况。
@Environment(\.managedobjectContext) var moc
@State private var date = Date()
@FetchRequest(
entity: Todo.entity(),
sortDescriptors: [
NSSortDescriptor(keyPath: \Todo.date, ascending: true)
]
) var todos: FetchedResults<Todo>
var dateFormatter: DateFormatter {
let formatter = DateFormatter()
formatter.dateStyle = .short
return formatter
}
func update(_ result : FetchedResults<Todo>)-> [[Todo]]{
return Dictionary(grouping: result){ (element : Todo) in
dateFormatter.string(from: element.date!)
}.values.map{$0}
}
var body: some View {
vstack {
List {
ForEach(update(todos), id: \.self) { (section: [Todo]) in
Section(header: Text( self.dateFormatter.string(from: section[0].date!))) {
ForEach(section, id: \.self) { todo in
HStack {
Text(todo.title ?? "")
Text("\(todo.date ?? Date(), formatter: self.dateFormatter)")
}
}
}
}.id(todos.count)
}
Form {
DatePicker(selection: $date, in: ...Date(), displayedComponents: .date) {
Text("Datum")
}
}
Button(action: {
let newTodo = Todo(context: self.moc)
newTodo.title = String(Int.random(in: 0 ..< 100))
newTodo.date = self.date
newTodo.id = UUID()
try? self.moc.save()
}, label: {
Text("Add new todo")
})
}
}
解决方法
为了简单起见,假设我要创建一个简单的待办事项应用程序。我的xcdatamodel中有一个实体Todo,其属性为id
,title
和date
和以下swiftui视图(如图所示):
import SwiftUI
struct ContentView: View {
@Environment(\.managedObjectContext) var moc
@State private var date = Date()
@FetchRequest(
entity: Todo.entity(),sortDescriptors: [
NSSortDescriptor(keyPath: \Todo.date,ascending: true)
]
) var todos: FetchedResults<Todo>
var dateFormatter: DateFormatter {
let formatter = DateFormatter()
formatter.dateStyle = .short
return formatter
}
var body: some View {
VStack {
List {
ForEach(todos,id: \.self) { todo in
HStack {
Text(todo.title ?? "")
Text("\(todo.date ?? Date(),formatter: self.dateFormatter)")
}
}
}
Form {
DatePicker(selection: $date,in: ...Date(),displayedComponents: .date) {
Text("Datum")
}
}
Button(action: {
let newTodo = Todo(context: self.moc)
newTodo.title = String(Int.random(in: 0 ..< 100))
newTodo.date = self.date
newTodo.id = UUID()
try? self.moc.save()
},label: {
Text("Add new todo")
})
}
}
}
待办事项在获取时按日期排序,并显示在这样的列表中:
我想基于每个待办事项各自的日期将列表分组(样机):
据我了解,这可以与该init()
函数中的Dictionary一起使用,但是我无法提出任何对远程有用的东西。有一种有效的数据分组方法吗?