Question

我正在进行网络呼叫并从API检索一些信息并将其存储在NSMutableArray中。当我试图将数组信息发送到另一个对象时，我碰壁了：
我没有任何错误。我无法访问另一个类中的数组信息。它在API类中打印得很好但在尝试访问另一个类时，数组打印为空。

这是我的API类，最顶层有NSMutableArray来保存信息：

class API: NSObject {

    var informationArray = NSMutableArray();

    func getEarthquakeInformation() {

        let session = NSURLSession.sharedSession()
        let urlString = "http://ehp2-earthquake.wr.usgs.gov/fdsnws/event/1/query?format=geojson&limit=20"
        let url = NSURL(string: urlString)!
        let request = NSURLRequest(URL: url)
        let task = session.dataTaskWithRequest(request){ data,response,downloadError in

            if let error = downloadError {
                 print("could not complete the request\(error)")
            } else {

                let parsedResult = try! NSJSONSerialization.JSONObjectWithData(data! , options: NSJSONReadingOptions.AllowFragments)
                let dataDict = parsedResult as! NSDictionary

                // This holds all the information we need from the API.
                if let result = dataDict["features"] {

                    for var i = 0; i < result.count; i++ {
                        self.informationArray.addObject(result[i])
                        print(self.informationArray[i]) 
                    }

                } else {
                    print("error")
                }

                //print("info from the array \(self.informationArray)")   
            }  
        }
        task.resume() 
    }
}

这是我试图将其发送到的类：MapViewController

 override func viewDidLoad() {
        super.viewDidLoad()

        // Instance of the api class
        let apiObject = API()
        apiObject.getEarthquakeInformation()
        print(apiObject.informationArray)

Answer 1

这里有几件事：

首先，请查看使用网络库（例如AlamoFire）

第二次，当你声明你的可变数组时，你应该以这种形式完成它（没有理由使用NSMutableArray（））：

var myArray = [ObjectType]()

第三，不要使用C风格的for循环，它们被标记为从Swift中删除。你应该迭代：

for item in result {
    //Do something with item.
}

，只要将数组“发送”到MapViewController对象即可。如果API对象存在于MapViewController中，那么您可以将API函数作为参数接受闭包。您可以将数组传递回闭包本身的MapViewController。或者您也可以使用通知。

希望这有帮助。

Answer 2

  let apiObject = API()
    // Your problem it here this method takes time to update informationArray
    apiObject.getEarthquakeInformation()
    // But this line print immediately while it's still empty.
    print(apiObject.informationArray)

你做的是

从informationArray课程中删除API并将其放入MapViewController

更改getEarthquakeInformation方法以获得竞争处理程序

class API: NSObject {

// remove it  //var informationArray = NSMutableArray();

func getEarthquakeInformation(compeletion: (informationArray: [AnyObject]!) ->()) {

    let session = NSURLSession.sharedSession()
    let urlString = "http://ehp2-earthquake.wr.usgs.gov/fdsnws/event/1/query?format=geojson&limit=20"
    let url = NSURL(string: urlString)!
    let request = NSURLRequest(URL: url)
    let task = session.dataTaskWithRequest(request){ data,response,downloadError in

        if let error = downloadError {
             print("could not complete the request\(error)")
        } else {

            let parsedResult = try! NSJSONSerialization.JSONObjectWithData(data! , options: NSJSONReadingOptions.AllowFragments)
            let dataDict = parsedResult as! NSDictionary

            // This holds all the information we need from the API.
            if let result = dataDict["features"] {
              compeletion(result)
            } else {
                print("error")
            }
        }    
    }

    task.resume()
}

然后在MapViewController

var informationArray: [AnyObject]!
override func viewDidLoad() {
   super.viewDidLoad()

    // Instance of the api class
    let apiObject = API()
    apiObject.getEarthquakeInformation() { [unowned self] (result) ->() in 
    self.inforamtionArray = result
    print(self.informationArray)
}

将NSMutableArray传递给Swift中的另一个对象

2 个答案: