ios - MainViewController 没有收到来自 NSNotificationCenter 的通知

Question

我的主类是一个 UITableViewController。我正在使用 ConnectionManager 类获取一些 JSON 数据，并使用 ItemManager 类对其进行解析。类之间的通信是使用 NotificationCenter 完成的。每当有来自 ConnectionManager 的响应时，它都会向 ItemManager 发送通知，然后对其进行解析。

ConnectionManager 发布通知，ItemManager 正确接收它们。我想使用相同的方法来更新我的 TableView 。问题出在我的主课上。解析完成后，它不会收到来自 ItemManager 的通知。

• ConnectionManager -> posts，ItemManager -> receives -- OK
• ItemManager -> posts, UITableViewController -> receives -- NOK

部分代码:

class ConnectionManager {

  private let URL = "http://foo.json"
  private var response: Data?

  init () {
    getData()
  }

  func getData() {
    let req = NSMutableURLRequest(url: NSURL(string: URL)! as URL)
    req.httpMethod = "GET"
    URLSession.shared.dataTask(with: req as URLRequest) { data, response, error in
      if error != nil {
        //HTTP request failed
        NSLog(error?.localizedDescription ?? "Unknown Error")
        NotificationCenter.default.post(name: Notification.Name(NotificationCenterKeys.NOK), object: nil)
      } else {
        //HTTP request succeeded
        self.response = data
        NotificationCenter.default.post(name: Notification.Name(NotificationCenterKeys.OK), object: nil)
      }
      }.resume()
  }
}

class ItemManager {
  private var cm: ConnectionManager
  private var items = [Item]()

  init() {
    self.cm = ConnectionManager()
    NotificationCenter.default.addObserver(self, selector: #selector(self.parseResponse), name: Notification.Name(NotificationCenterKeys.OK), object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(self.noData), name: Notification.Name(NotificationCenterKeys.NOK), object: nil)
  }

  @objc private func noData() {
    NSLog("No data to parse")
  }

  @objc private func parseResponse() {
    do {
      if let data = cm.getResponse() {
        let items: NSDictionary = try JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions.mutableContainers) as! NSDictionary
        let rawItems = items["numbers"] as! [Int]
        self.items = parseItems(rawItems: rawItems)
    NotificationCenter.default.post(name: Notification.Name(NotificationCenterKeys.PARSED), object: nil)

      }
    } catch {
      print("Error deserializing JSON: \(error)")
    }
  }

最后是我的 UITableViewController:

class MainViewTableViewController: UITableViewController {

  var items = [Item]()
  var dataAvailable = false
  var im = ItemManager()
  var dataLabel = "Loading Data..."

  override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: #selector(self.updateTable), name: Notification.Name(NotificationCenterKeys.PARSED), object: nil)
    setTable()
  }

  @objc func updateTable() {
    if im.getItems()?.count != 0 {
      items = im.getItems()!
      dataAvailable = true
    } else {
      dataAvailable = false
      dataLabel = "No Data Available"
    }
    self.tableView.reloadData()
  }

  override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
  }

  func setTable() {
    title = "Test"
    tableView.rowHeight = 40
  }

  // MARK: - Table view data source

  override func numberOfSections(in tableView: UITableView) -> Int {
    var numOfSections = 0
    if dataAvailable {
      numOfSections = 4
      return numOfSections
    } else {
      let noDataLabel: UILabel = UILabel(frame: CGRect(x: 0, y: 0, width: tableView.bounds.size.width, height: tableView.bounds.size.height))
      noDataLabel.text = dataLabel
      noDataLabel.textColor = UIColor.black
      noDataLabel.textAlignment = .center
      tableView.backgroundView = noDataLabel
      tableView.separatorStyle = .none
    }
    return numOfSections
  }

  override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return getNumOfItemsPerSection(section: section)
  }

  override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! TableViewCell
    guard let sectionNumber = SectionNumber(rawValue: indexPath.section) else { return cell }
    let elements = self.items.filter({ $0.sectionNumber == sectionNumber })
    cell.nameLabel?.text = elements[indexPath.row].itemNumber?.description
    if elements[indexPath.row].checkmark {
      cell.accessoryType = .checkmark
    } else { cell.accessoryType = .none }
    return cell
  }

  func getNumOfItemsPerSection(section: Int) -> Int {
    guard let sectionNumber = SectionNumber(rawValue: section) else { return 0 }
    return self.items.filter({ $0.sectionNumber == sectionNumber }).count
  }

  override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
    return "Section \(section + 1)"
  }
}

Answer 1

发现问题了!收到通知后我正在注册观察者(ups)

class MainViewTableViewController: UITableViewController {

  var items = [Item]()
  var dataAvailable = false
  var im: ItemManager? = nil

  override func viewDidLoad() {
    super.viewDidLoad()
    setTable()
    NotificationCenter.default.addObserver(self, selector: #selector(self.updateTable),
                                           name: Notification.Name(NotificationCenterKeys.END), object: nil)
    im = ItemManager()
  }

...

现在工作得很好:-)