CoreData 和 FetchRequest，ForEach 和 "Cannot invoke initializer" 的问题

Question

我刚刚迁移到使用CoreDate而不是简单的集合。我使用的是 iOS13 beta 8 和 Xcode11 beta 6。

struct BeaconList: View {
@Environment(.managedObjectContext) var managedObjectContext
@FetchRequest(fetchRequest: fetchRequest(), animation: nil) var beacons: FetchedResults<Beacon>
static func fetchRequest() -> NSFetchRequest<Beacon> {
let request: NSFetchRequest<Beacon> = Beacon.fetchRequest()
request.sortDescriptors = [NSSortDescriptor(key: "id", ascending: true)]
return request
}
func buildView(name: String, beacons: [Beacon]) -> AnyView {
return AnyView (
Section(header: Text(name)) {
ForEach(beacons) { beacon in
BeaconListEntry(beacon: beacon)
}
}
)
}
var body: some View {
TabView {
NavigationView {
List {
buildView(name: "MY BEACONS", beacons: beacons.filter { $0.isActive })
}
.navigationBarTitle("Beacons")
.listStyle(GroupedListStyle())
.navigationBarItems(trailing: addButton)
}
.tabItem {
Image(systemName: "antenna.radiowaves.left.and.right")
Text("Beacons")
}
}
}

BeaconListEntry如下：

struct BeaconListEntry : View {
@Binding var beacon: Beacon
var body: some View {
HStack {
Text(verbatim: beacon.name!)
}
}
}

(请忽略强制解包，仅供测试之用(

当我在重写之前将其与集合一起使用时，它起作用了，但现在我收到消息

Cannot invoke initializer for type 'ForEach<_, _, _>' with an argument list of type '([Beacon], @escaping (Binding<Beacon>) -> BeaconListEntry)'

和

1. Overloads for 'ForEach<_, _, _>' exist with these partially matching parameter lists: (Data, content: @escaping (Data.Element) -> Content), (Range<Int>, content: @escaping (Int) -> Content)

知道去哪里看吗？这是使用FetchedResults的正确方法吗？

Answer 1

BeaconListEntry

初始值设定项需要一个类型为Binding的参数，因此您应该按如下方式修改调用：

BeaconListEntry(beacon: .constant(beacon))