ios - 解析 JSON 数据时无法将字符串附加到数组

Question

我在存储从 JSON 源数据检索的结果时遇到困难。我已确认能够打印检索到的数据，但无法将其存储到我的本地数组中。

我的最终目标是在 UITableView 中实际打印结果。

下面是我的相关 TableView Controller 的代码:

import UIKit

class CommunityActivityTableViewController: UITableViewController {
    var displayNameArr = [String]()
    var postDateArr = [String]()
    var postDetailArr = [String]()
    var testArr = ["teaad"]

    override func viewDidLoad() {
        super.viewDidLoad()
        parseJson()
        print(self.displayNameArr.count) //returns 0
        print(self.postDateArr.count) //returns 0
        print(self.postDetailArr.count) //returns 0
        print(self.testArr.count)
        print("end")

    }
    override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
        // #warning Incomplete implementation, return the number of sections

        return 1
    }

    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

        // #warning Incomplete implementation, return the number of rows

        return self.displayNameArr.count
    }



    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        print("3")
        let cell = tableView.dequeueReusableCellWithIdentifier("Cell_activity", forIndexPath: indexPath)



        print("hi")
        cell.textLabel?.text = "hi"
        cell.detailTextLabel?.text = "test"

        return cell
    }
    override func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
        return UITableViewAutomaticDimension
    }
    override func tableView(tableView: UITableView, estimatedHeightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
        return UITableViewAutomaticDimension
    }
    func makeAttributedString(title title: String, subtitle: String) -> NSAttributedString {
        let titleAttributes = [NSFontAttributeName: UIFont.preferredFontForTextStyle(UIFontTextStyleHeadline), NSForegroundColorAttributeName: UIColor.purpleColor()]
        let subtitleAttributes = [NSFontAttributeName: UIFont.preferredFontForTextStyle(UIFontTextStyleSubheadline)]

        let titleString = NSMutableAttributedString(string: "\(title)\n", attributes: titleAttributes)
        let subtitleString = NSAttributedString(string: subtitle, attributes: subtitleAttributes)

        titleString.appendAttributedString(subtitleString)

        return titleString
    }
    func parseJson(){
        //MARK: JSON parsing
        let requestURL: NSURL = NSURL(string: "<sanitised>")!
        let urlRequest: NSMutableURLRequest = NSMutableURLRequest(URL: requestURL)
        let session = NSURLSession.sharedSession()
        let task = session.dataTaskWithRequest(urlRequest) {
            (data, response, error) -> Void in

            let httpResponse = response as! NSHTTPURLResponse
            let statusCode = httpResponse.statusCode

            if (statusCode == 200) {
                print("Everyone is fine, file downloaded successfully.")

                do{

                    let json = try NSJSONSerialization.JSONObjectWithData(data!, options:.AllowFragments)

                    if let results = json["result"] as? [[String: AnyObject]] {

                        for result in results {

                            if let lastname = result["last_name"] as? String {

                                if let postdate = result["timestamp"] as? String {
                                    if let firstname = result["first_name"] as? String {
                                        if let postdetails = result["post_details"] as? String {

                                            let displayname = firstname + " " + lastname
                                            //print(displayname)
                                            self.displayNameArr.append(displayname)
                                            self.postDateArr.append(postdate)
                                            self.postDetailArr.append(postdetails)
                                            self.testArr.append("haha")


                                        }
                                    }

                                }

                            }
                        }

                    }

                }catch {
                    print("Error with Json: \(error)")
                }

            }
        }

        task.resume()}


}

根据上面的代码，displaynamearr.count、postDateArr.count 和 postDetailArr.count 的打印结果在 parseJson() 方法应该返回大于 0 的结果时返回 0。

我已经打印了显示名称、游戏后和帖子详细信息变量，它们都包含数据，因此问题不在于数据的提取，而在于将数据附加到数组中。

感谢提供的任何帮助，谢谢!基于 Xcode 7 和 Swift 2.2 开发由于信息的敏感性，清理了我的 JSON 源(我已验证信息检索正常)

Answer 1

dataTaskWithRequest() 是异步数据加载。它在后台线程上加载，确保您的 UI 不会卡住。因此，当您执行此操作时，您的数组将为空，因此会出现错误。您需要像这样的完成处理程序:

   func parseJson(completion: (isDone: Bool) -> ()){

///code

for result in results {

                            if let lastname = result["last_name"] as? String {

                                if let postdate = result["timestamp"] as? String {
                                    if let firstname = result["first_name"] as? String {
                                        if let postdetails = result["post_details"] as? String {

                                            let displayname = firstname + " " + lastname
                                            //print(displayname)
                                            self.displayNameArr.append(displayname)
                                            self.postDateArr.append(postdate)
                                            self.postDetailArr.append(postdetails)
  self.testArr.append("haha")


       }
completion(isDone: True)

   }



}

现在在 viewDidLoad 中:

 override func viewDidLoad() {
            super.viewDidLoad()
            parseJson(){ success in
            if success{
            print(self.displayNameArr.count) //returns a value
            print(self.postDateArr.count) //returns a value
            print(self.postDetailArr.count) //returns a value
            print(self.testArr.count) //This wont because I havent added it in the completion handler
            print("end")
       self.tableView.reloadData()
   }
   }
    }