带有 onDelete 和确认警报的 Swiftui WatchKit 列表无法正确更新 tableview [英] Swiftui WatchKit List with onDelete and confirm alert does not update tableview correctly
问题描述
有人能指出我如何使用确认删除功能实现简单列表的正确方向，或者至少在这里展示最佳实践.
Can someone point me in the right direction on how to implement a simple list with a confirm remove-function or at least show best practice here.
如果警报部分被删除并且立即删除操作，下面的代码将起作用.不知何故，确认警报的呈现使得删除操作对错误的人员列表起作用.第一次删除也会给出控制台警告:
Below code will work if the alert-part is removed and delete action is immediate. Somehow, the presentation of the confirmation-alert makes the the deletion act on the wrong list of persons. First removal also gives a console warning:
[TableView] 仅警告一次:UITableView 被告知在不在视图层次结构中布局其可见单元格和其他内容(表视图或其父视图之一尚未添加到窗口中).这可能会通过强制 table view 中的视图在没有准确信息(例如 table view bounds、trait collection、layout margins、safe area insets 等)的情况下加载和执行布局而导致错误，并且还会由于额外的布局传递而导致不必要的性能开销.在 UITableViewAlertForLayoutOutsideViewHierarchy 处创建一个符号断点，以便在调试器中捕获此问题并查看导致此问题发生的原因，因此您可以尽可能避免此操作，或者将其推迟到将表视图添加到窗口中.
[TableView] Warning once only: UITableView was told to layout its visible cells and other contents without being in the view hierarchy (the table view or one of its superviews has not been added to a window). This may cause bugs by forcing views inside the table view to load and perform layout without accurate information (e.g. table view bounds, trait collection, layout margins, safe area insets, etc), and will also cause unnecessary performance overhead due to extra layout passes. Make a symbolic breakpoint at UITableViewAlertForLayoutOutsideViewHierarchy to catch this in the debugger and see what caused this to occur, so you can avoid this action altogether if possible, or defer it until the table view has been added to a window.
但是，我不知道如何在不删除警报的情况下解决此问题.顺便说一句，这个确切的代码在我相信我的 mac 更新 xcode 之前几周前就起作用了.
However, I have no idea on how to solve this without removing the alert. By the way, this exact code worked a couple of weeks ago before my mac updated xcode i believe.
import Foundation
import SwiftUI
import Combine
struct Person: Identifiable{
var id: Int
var name: String
init(id: Int, name: String){
self.id = id
self.name = name
}
}
class People: ObservableObject{
@Published var people: [Person]
init(){
self.people = [
Person(id: 1, name:"One"),
Person(id: 2, name:"Two"),
Person(id: 3, name:"Three"),
Person(id: 4, name:"Four")]
}
}
struct ContentView: View {
@ObservedObject var mypeople: People = People()
@State private var showConfirm = false
@State private var idx = 0
func setDeletIndex(at idxs:IndexSet) {
self.showConfirm = true
self.idx = idxs.first!
}
func delete() {
self.mypeople.people.remove(at: idx)
}
var body: some View {
VStack {
List {
Text("Currently \(mypeople.people.count) persons").font(.footnote)
.alert(isPresented: $showConfirm) {
Alert(title: Text("Delete"), message: Text("Sure?"),
primaryButton: .cancel(),
secondaryButton: .destructive(Text("Delete")) {
self.delete()
})
}
ForEach(mypeople.people){ person in
Text("\(person.name)")
}.onDelete { self.setDeletIndex(at: $0) }
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
推荐答案
问题是由于更新alert closed &列表记录删除.解决方法是延迟删除，如下(使用 Xcode 11.4 测试)
The problem is due to conflict of updating alert closing & List record removing. The working workaround is to delay deleting, as below (tested with Xcode 11.4)
Text("Currently \(mypeople.people.count) persons").font(.footnote)
.alert(isPresented: $showConfirm) {
Alert(title: Text("Delete"), message: Text("Sure?"),
primaryButton: .cancel(),
secondaryButton: .destructive(Text("Delete")) {
DispatchQueue.main.asyncAfter(deadline: .now() + 0.2) { // here !!
self.delete()
}
})
}
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