仅当所有记录都在Swift中获取时，如何才能将从json异步获取的记录添加到数组中? [英] How can I add records fetched asynchronously from json to the array only when all records are fetched in Swift?

问题描述

我正在开发苹果地图的市场集群(这是插件 https://github.com/ribl/FBAnnotationClusteringSwift )，我想一次在地图上显示所有记录-为此，我需要从远程Web服务下载所有记录，将其添加到json(我已经完成了)，然后添加所有指向数组.

I'm working on a market cluster for apple maps (here is the plugin https://github.com/ribl/FBAnnotationClusteringSwift ) and I want to display all records on my map at once - for that I need to download all the records from remote webservice, add it to json (I've already done that) and then add all fetched points to an array.

我的代码如下:

let clusteringManager = FBClusteringManager()
var array:[FBAnnotation] = []

func loadInitialData() {
    RestApiManager.sharedInstance.getRequests { json in
        if let jsonData = json.array {
           for requestJSON in jsonData {
               dispatch_async(dispatch_get_main_queue(),{
               if let request = SingleRequest.fromJSON(requestJSON){

                let pin = FBAnnotation()
                pin.coordinate = CLLocationCoordinate2D(latitude: request.latitude, longitude: request.longitude)
                self.array.append(pin)

                }
                })
             }
          }
     }
}

如您所见，我将所有pin附加到数组中，有时需要在这里使用此数组:

as you can see I'm appending all pins to the array and at some point I need to use this array here:

self.clusteringManager.addAnnotations(array)

我以为我可以在方法loadInitialData的最后写上面的行，但是数组仍然是空的.我应该如何更改代码，以便在array充满数据时调用addAnnotations方法?

I thought I could just write the line above at the very end of my method loadInitialData, but then the array is still empty. How should I change my code so that it invokes the addAnnotations method when the array is filled with data?

===编辑

只是一个小小的补充-我在viewDidLoad

Just a small add on - I call the method loadInitialData in viewDidLoad

override func viewDidLoad() {
    super.viewDidLoad()
    mapView.delegate = self
    loadInitialData()
}

推荐答案

您可能要使用NSOperation. API的方法addDependency(:)正是您要寻找的. 代码可能看起来像这样:

You may want to use NSOperation. It's API has method addDependency(:) that is just what you're looking for. The code might look like this:

let queue = NSOperationQueue()
var operations : [NSOperation] = []
RestApiManager.sharedInstance.getRequests { json in
    if let jsonData = json.array {
       for requestJSON in jsonData {
           let newOperation = NSBlockOperation {
               SingleRequest.fromJSON(requestJSON){

               let pin = FBAnnotation()
               pin.coordinate = CLLocationCoordinate2D(latitude: request.latitude, longitude: request.longitude)
               self.array.append(pin)

            } 
            operations.append(newOperation)
           }

         }
      }
    let finalOperation = NSBlockOperation() {
         ///array has been populated
         ///proceed with it
    }

    operations.forEach { $0.addDependency(finalOperation) }
    operations.append(finalOpeartion)
    operationQueue.addOperations(operations)
 }

这篇关于仅当所有记录都在Swift中获取时，如何才能将从json异步获取的记录添加到数组中?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！