ios - 为什么 "self"在我的 QueryOperation 中阻止来自 CloudKit 的数据

Question

我在 Cloudkit 的数据库中有多个 CKRecords。我将这些 CKRecords 转换为我的 map 的注释。自从我不得不在我的查询操作中的变量 var annotation = MKPointAnnotation() 之前添加 self 之后，它只向我的 map 加载了一个注释。为什么会这样，我该如何解决？？？任何帮助都会很棒!

我如何获取记录 -

 var points: [MKPointAnnotation] = []
 var annotation = MKPointAnnotation()
 let database = CKContainer.default().publicCloudDatabase

 func fetchTruck() {

let truePredicate = NSPredicate(value: true)
let eventQuery = CKQuery(recordType: "User", predicate: truePredicate)
let queryOperation = CKQueryOperation(query: eventQuery)


queryOperation.recordFetchedBlock = {  (record) in



    self.points.append(self.annotation)

    self.annotation.title = record["username"] as? String
    self.annotation.subtitle = record["hours"] as? String
    if let location = record["location"] as? CLLocation {
        self.annotation.coordinate = location.coordinate
    }

    print("recordFetchedBlock: \(record)")

    self.mapView.addAnnotation(self.annotation)

    }




        self.database.add(queryOperation)

}

Answer 1

在更详细地查看您的代码后，我认为问题在于您始终使用相同的注释。 MKPointAnnotation 是一个类，一个引用值，这意味着每次您为 self.annotation 赋值时，您都在更改引用，而不是创建一个新引用。

您正在 CKQueryOperation 闭包内修改您的应用程序 UI (mapView)。尝试在主线程中运行修改代码

尝试类似...

var points: [MKPointAnnotation] = []
let database = CKContainer.default().publicCloudDatabase

func fetchTruck() 
{
    let truePredicate = NSPredicate(value: true)

    let eventQuery = CKQuery(recordType: "User", predicate: truePredicate)
    let queryOperation = CKQueryOperation(query: eventQuery)

    queryOperation.recordFetchedBlock = {  (record) in
        var annotation = MKPointAnnotation()

        annotation.title = record["username"] as? String
        annotation.subtitle = record["hours"] as? String
        if let location = record["location"] as? CLLocation 
        {
            annotation.coordinate = location.coordinate
        }

        self.points.append(annotation)

        DispatchQueue.main.async
        {
            self.mapView.addAnnotation(annotation)
        }

        print("recordFetchedBlock: \(record)")
    }

    self.database.add(queryOperation)
}