等待数据加载到模型中，然后在 ViewController 中访问它们

Question

我正在努力让我的 ViewVontroller 知道何时成功加载了所有数据。我的 ViewController 有一个 Stop 对象列表，所有这些对象都有一个 Bus 对象列表。在每个 Stop 中，我调用一个 API 并填充 Bus 对象列表。我在每个 Stop 对象中都得到了完成块，用于了解作业何时完成。但是，当我想在 ViewController 中使用它们时，我几乎不知道该怎么做。在我使用它们之前，我想确保每个 Stop 对象都有一个完整的总线列表。目前的解决方案是等待 2 秒然后使用它们，这不是一个更好的解决方案，但它给了我一些数据来处理。有什么建议么？我想我不能从我的模型中的 ViewController 调用方法，因为这会破坏 MVC 模式，对吧？

class LoadingViewController: UIViewController {

var nearbyStops = [Stop]()

override func viewDidLoad() {
    super.viewDidLoad()
    animateLogoEntry()

    GPSUtil.sharedInstance.startGPS()

    stopsNearby(initialLocation, maxRadius: 1000, maxNumber: 5)

}

// MARK: - API work

/**
 Assigns the array of Stops to the nearby stops
*/
func stopsNearby(location: CLLocationCoordinate2D, maxRadius: Int, maxNumber: Int) {
    APIHelper.sharedInstance.getStopsNearby(location, maxRadius: maxRadius, maxNumber: maxNumber) { (result) -> Void in
        self.nearbyStops = result!
        self.test()
    }
}

func test() {
    let time = dispatch_time(dispatch_time_t(DISPATCH_TIME_NOW), 2 * Int64(NSEC_PER_SEC))
    dispatch_after(time, dispatch_get_main_queue()) {
        }
        for item in self.nearbyStops {
            let items = item.getDepartures()
            print(item.name!)
            for element in items {
                element.timeUtilDeparture()
                print("    " + element.name + " - " + element.direction)
                print("          \(element.times)")
                print(element.timeUntilDepartureList)
            }
        }
    }
}

class Stop: NSObject, MKAnnotation {

var departures = [Departure]()
var busses = [Bus]()

init(name: String, coordinate: CLLocationCoordinate2D, stopID: Int64, distance: Int) {
    self.name = name
    self.coordinate = coordinate
    self.stopID = stopID
    self.distance = distance
    super.init()
    loadDepartures() { (result) -> Void in
        self.sanitizeBusDepartures( { (result) -> Void in
            // THE CURRENT OBJECT IS LOADED WITH DATA
        })
    }
}

/**
    Loads the departures for the current stop.
*/
private func loadDepartures(completion: ((result: Bool) -> Void)!) {
    let date = NSDate()
    let calender = NSCalendar.currentCalendar()
    let components = calender.components([.Hour, .Minute, .Day, .Month, .Year], fromDate: date)
    let currentHour = components.hour
    let currentMinute = components.minute
    let currentDay = components.day
    let currentMonth = components.month
    let currentYear = components.year

    let currentDate = "\(currentDay).\(currentMonth).\(currentYear)"
    let currentTime = "\(currentHour):\(currentMinute)"

    let specificURL = "URL"

    let url: NSURL = NSURL(string: specificURL)!
    let session = NSURLSession.sharedSession()

    let task = session.dataTaskWithURL(url)
    { (data, resonse, error) -> Void in
        if error == nil {

            let dataReturned = JSON(data: data!)

            let departures = dataReturned["DepartureBoard"]["Departure"]
            for (_, value):(String, JSON) in departures {
                let busName = value["name"].stringValue
                let stop = value["stop"].stringValue
                let time = value["time"].stringValue
                let delay = value["messages"].intValue
                let date = value["date"].stringValue
                let finalStop = value["finalStop"].stringValue
                let direction = value["direction"].stringValue
                let journeyDetailUrl = value["JourneyDetailRef"]["ref"].stringValue

                self.departures.append(
                    Departure(name: busName,
                        stop: stop,
                        time: time,
                        delay: delay,
                        date: date,
                        finalStop: finalStop,
                        direction: direction,
                        journeyDetailLink: journeyDetailUrl))
            }
        }

        completion(result: true)
    }

    task.resume()
}

private func sanitizeBusDepartures(completion: ((result: Bool) -> Void)!) {
        var tempList = [Bus]()

        for item in departures {
            tempList.append(Bus(name: item.name!, direction: item.direction!, times: item.time!))
        }

        for item in tempList {
            if busses.contains(item) {
                let indexOfElement = busses.indexOf(item)
                busses[indexOfElement!].times += item.times
            } else {
                busses.append(item)
            }

        }

        completion(result: true)
    }

正如您在上面看到的，每个 Bus 对象都从它自己的 URL 加载它自己的数据，所以在我的 ViewController 中，我想确保每个 Stop 对象都加载了数据。

Answer 1

添加所有元素时发出通知，例如：

self.departures.append(
                    Departure(name: busName,
                        stop: stop,
                        time: time,
                        delay: delay,
                        date: date,
                        finalStop: finalStop,
                        direction: direction,
                        journeyDetailLink: journeyDetailUrl))
            }
        }

        completion(result: true)
    NSNotificationCenter.defaultCenter().postNotificationName("Completed", object: nil)
    }

    task.resume()
}

private func sanitizeBusDepartures(completion: ((result: Bool) -> Void)!) {
        var tempList = [Bus]()

        for item in departures {
            tempList.append(Bus(name: item.name!, direction: item.direction!, times: item.time!))
        }

        for item in tempList {
            if busses.contains(item) {
                let indexOfElement = busses.indexOf(item)
                busses[indexOfElement!].times += item.times
            } else {
                busses.append(item)
            }

        }

        completion(result: true)

    }

然后在test()收到：

func test(notification: NSNotification){
 NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(self.test(_:)), name: "Completed", object: nil)
//Your code..
}

然后移除观察者：

deinit{
NSNotificationCenter.defaultCenter().removeObserver(self)
}

Answer 2

在处理异步请求时对时间做出假设是个坏主意，是的，dispatch_groups 会起作用，但我提出了一个更简单的解决方案，委托，创建协议 StopDelegate 或一些对您有意义的名称，每个 Stop 对象都可以有一个 stopDelegate 变量：

protocol StopDelegate: class {
   func stopDidFetchDepartures(stop: Stop)
}

class Stop: NSObject, MKAnnotation {
   weak var stopDelegate: StopDelegate?
   ...
}

Stop 对象在出发和公共汽车信息准备就绪时通知它的委托：

loadDepartures() { (result) -> Void in
    self.sanitizeBusDepartures( { (result) -> Void in
        // THE CURRENT OBJECT IS LOADED WITH DATA
        self.stopDelegate. stopDidFetchDepartures(self)
    })
}

当你分配 LoadingViewController 的 nearbyStops 变量时，你可以将控制器分配为每个 stop 对象的委托并实现委托，你还需要一个计数器已完成加载的站点：

var stopDeparturesFetchedCount = 0

func stopDidFetchDepartures(stop: Stop) {
   stopDeparturesFetchedCount += 1
   if stopDeparturesFetchedCount >= nearbyStops.count {
      print("All stops finished loading")
   }
}

Answer 3

确实不应该违反 MVC，而使用 same.You 应该采用 MVVM 模式而不是 MVC。以下是详尽的教程，可将其合并到您的 ios 应用程序中。 https://www.raywenderlich.com/74106/mvvm-tutorial-with-reactivecocoa-part-1

等待数据加载到模型中，然后在 ViewController 中访问它们

Wait for data to get loaded in model before accessing them in ViewController

json

viewcontroller

ios

swift