未添加到数组中的对象 - swift iOS

Question

我正在尝试将 Task 对象添加到一个名为 tasks 的数组中，然后按类别将它们过滤到另一个名为 filteredTasks 的数组中。

    var tasks = [Task]()
var filteredTasks = [Task]()    

override func viewDidLoad() {
    super.viewDidLoad()
    print(categoryPass)
    loadTasks()
    filterTasks(categoryPass!)
    if filteredTasks.isEmpty {
        filterTasks(categoryPass!)
    }
    print(filteredTasks)
    self.locationManager.desiredAccuracy = kCLLocationAccuracyBest
    self.locationManager.requestWhenInUseAuthorization()
    self.locationManager.startUpdatingLocation()
    self.locationManager.delegate = self
    tableView.registerClass(UITableViewCell.self, forCellReuseIdentifier: "cell")
    tableView.delegate = self
    tableView.dataSource = self

    // Do any additional setup after loading the view, typically from a nib.
}


func loadTasks() {
    var taskTitle: String?
    var id: String?
    var distance: Double?
    var category: String?

    var locationDict: [String:CLLocation] = [:]
    var refHandle = self.ref.child("tasks").observeEventType(FIRDataEventType.Value, withBlock: { (snapshot) in
        self.tasksDict = snapshot.value as? NSDictionary
        for i in 0 ..< self.tasksDict!.count {
            let taskId = self.tasksDict!.allKeys[i] as! String
            print ("1")
            id = taskId
           print (taskId)
            let task = self.tasksDict!.objectForKey(taskId) as! NSDictionary
            print ("2")
            let lat = task.objectForKey("latitude") as! String
            let long = task.objectForKey("longitude") as! String
            let latNum = Double(lat)! as CLLocationDegrees
            let longNum = Double(long)! as CLLocationDegrees
            taskTitle = task.objectForKey("title") as? String
            category = task.objectForKey("category") as? String
            print("3")
           // print (taskTitle)
            //print (category)

            let pointLocation = CLLocation(latitude: latNum, longitude: longNum)
            locationDict[taskId] = pointLocation
            if (self.locationCurrent == nil) {
                self.locationCurrent = self.locationManager.location!
            }
            print("4")
            distance = round(self.locationCurrent!.distanceFromLocation(pointLocation))
            var taskAddition = Task(title: taskTitle, id: id, distance: distance, category: category)
            print (taskAddition)
            self.tasks += [taskAddition]

        }
    })
}

func filterTasks(searchText: String, scope: String = "All") {
    print("filter")
    for i in 0 ..< tasks.count {
        let taskId = tasksDict!.allKeys[i] as! String
        //  print (taskId)
        let task = tasksDict!.objectForKey(taskId) as! NSDictionary
        let taskCategory = task.objectForKey("category") as! String
        if (taskCategory.lowercaseString.containsString(searchText.lowercaseString)) {
            filteredTasks.append(task[i] as! Task)
        }

    }

    self.tableView.reloadData()
}

数字 1、2、3 和 4 都在控制台中打印出来，但是如果我尝试打印出任务或过滤任务，我得到 [] 并且计数为 0。是否有没有任务没有的原因被添加到数组中？

Answer 1

你不能那样做。 observeEventType 方法是异步的。它需要一个闭包作为参数。它在闭包运行之前立即返回。

你需要重写你的 loadTasks 函数来完成闭包。然后，一旦填充了任务数组，您就可以使用要执行的代码来调用它。有关工作示例，请参阅我对此线程的回答：

how to return value after the execution of the block? Swift