为什么我无法从 Alamofire 获取请求结果

Question

我无法获得 Alamofire 请求的结果。因此，我创建了从 json 异步调用获得的数组的输出。我无法从调度 {...} 中获取 resultArray。当我添加 println调试代码。第二个出现在第一个之前。 我只想使用 resultArray 从 Alamofire 获取数据以显示在 UIPickerView 中。请帮助！！！

这是我的代码

import UIKit
import Alamofire

class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource{

@IBOutlet var venuePicker : UIPickerView?

var resultOld = [String:String]() // i need it to get only value from json

var result : [String]?

let refreshControl = UIRefreshControl()

override func viewDidLoad() {

    if result == nil {
        populateVenues ({ (error, result) -> Void in
            self.result = result as? [String]
            self.venuePicker?.reloadAllComponents()
        })
    }
}

func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
    return 1
}

func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    if result != nil{
        return result!.count// Why i can't use result?.count instead of result!.count
    }
    else{
        return 0
    }
}

func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
    if result != nil{
        println(result)
        return result?[row]
    }
    else{
        return "..."
    }
}

func populateVenues(completion : (error: NSError?,result : AnyObject?) -> Void){
    Alamofire.request(.POST, "http://xxxx.xxxx.xxx").responseJSON() {
        (_, _, jsonData, error) in

        if error == nil{
            var venues = JSON(jsonData!)

            for (k, v) in venues {

                self.resultOld[k] = v.arrayValue[0].stringValue
            }

            self.result = self.resultOld.values.array

            completion(error: nil,result: self.result)
        }
        else{
            println("Error!!")
            completion(error: error!,result: nil)
        }
    }
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

这是我在控制台的输出

The 2st result array : []
The 1st result array : [ORIX Kobe Nyusatsu, NPS Sendai Nyusatsu, JU Gunma, KAA Kyoto, JU Ibaraki, USS Gunma, ISUZU Kobe, NAA Osaka Nyusatsu, SMAP Sapporo Nyusatsu, L-Up PKobeNyusatsu, ARAI Sendai, TAA Minami Kyushu, NPS Oyama Nyusatsu, CAA Tokyo, JU Toyama, USS Shikoku, NPS Gifu Nyusatsu, NAA Fukuoka, KCAA Yamaguchi, JU Fukuoka, LAA Kansai, JAA, TAA Kinki, USS Sapporo, JU Miyagi, USS Fukuoka, JU Tokyo]

我真的需要知道发生在我身上的事情以及为什么我不能先得到异步调用的结果。

Answer 1

所以异步调用在另一个线程上执行。因此，当您调用函数populateVenue() 时，populateVenue() 函数不会在println("The 2st result array : \(self.resultArray)" ) 之前完成。如果您将populateVenue() 设置为关闭，则不会发生这种情况。 示例：

override func viewDidLoad() {

   super.viewDidLoad()

   populateVenue( { (error, result) -> Void in 
      println("The 2st result array : \(self.resultArray)" )
   })
}

func populateVenue(completion: (error: NSError?, result: AnyObject?) -> Void) {
    Alamofire.request(.POST, "http://localhost:8080/ws/automobile/global/auction/latest/venues").responseJSON() {
    (_, _, jsonData, error) in

       if error == nil {
          // do whatever you need
          // Note that result is whatever data you retrieved
          completion(nil, result)
       } else {
           println("Errror")
           completion(error!, nil)
       }
   }
}

编辑：

我仍在努力了解您的问题，但这是我最好的选择。请注意，我不知道 resultOld 的用途是什么，所以我将其删除。如果您绝对需要它，可以将其重新添加。我的设计是使属性可选，并在完成块中返回结果。然后在 viewDidLoad 中，你可以初始化属性数组并重新加载你的屏幕。

@IBOutlet var venuePicker : UIPickerView?

// Try making this optional so you can tell when the network call is completed
var result: [String]?

var error = "Error"

let refreshControl = UIRefreshControl()

override func viewDidLoad() {
    if result == nil {
       populateVenues ( { (result) -> Void in
          self.result = result
          self.venuePicker?.reloadAllComponents()
       })
    }
}

func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
    return 1
}

func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
     if result != nil {
        return result.count
     } else {
        return 0
     }
}

func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {

    return result[row]
}

func populateVenues(completion : (result : [String]?) -> Void){
    Alamofire.request(.POST, "http://localhost:8080/ws/automobile/global/auction/latest/venues").responseJSON() {
        (_, _, jsonData, error) in

        if error == nil{
            var venues = JSON(jsonData!)

            for (k, v) in venues {

                resultOld[k] = v.arrayValue[0].stringValue

            }

            result = resultOld.values.array

            completion(result: result)
        }
        else{
            println("Error!!")
            completion(result: nil)
        }
    }
}