如何使用SwiftUI从CloudKit检索数据

Question

我正在使用SwiftUI制作应用程序并将数据存储在ICloud上。因为我可以找到的所有代码都与Swift和viewDidLoad和TableView有关，但是这并不适用。我已经编写了代码，似乎可以检索它，但不会将其返回给ObservableObject以便能够在SwiftUI中显示]

ObservableObject文件：-

import SwiftUI
import Combine

final class ObservedData: ObservableObject {
    @Published var venues = venuesData
}
检索数据的查询

import SwiftUI
import CloudKit

var venuesData: [Venue] = loadVenues()

func loadVenues() -> [Venue] {

    var data = [Venue]()

    let pred = NSPredicate(value: true)
    let sort = NSSortDescriptor(key: "id", ascending: true)
    let query = CKQuery(recordType: "DeptfordHopData", predicate: pred)
    query.sortDescriptors = [sort]

    let operation = CKQueryOperation(query: query)
    operation.desiredKeys = ["id","name", "address"]
    operation.resultsLimit = 50

    var newVenues = [Venue]()

    operation.recordFetchedBlock = { record in
        let venue = Venue()
        venue.racordID = record.recordID
        venue.id = record["id"]
        venue.name = record["name"]
        venue.address = record["address"]
        newVenues.append(venue)
    }

    operation.queryCompletionBlock = {(cursor, error) in
        DispatchQueue.main.async {
            if error == nil {
                data = newVenues
            } else {
                print(error!.localizedDescription)
            }
        }
    }

    CKContainer.default().publicCloudDatabase.add(operation)

    return data
}
我有数据显示何时中断数据但未传递给会场数据

我正在使用SwiftUI制作应用程序并将数据存储在ICloud上。因为我可以找到的所有代码都与Swift和viewDidLoad和TableView有关，但是这并不适用。我已经编写了代码，并且...

Answer 1

查询操作异步运行。当您将操作添加到数据库时，框架将在后台运行查询，并立即将控制权返回给您的函数，该函数会立即返回data，该值仍设置为空数组。