MainViewController不会从NSNotificationCenter获取通知

Question

我的主类是一个UITableViewController。 我使用ConnectionManager类获取一些JSON数据，并使用ItemManager类对其进行解析。类之间的通信使用NotificationCenter完成。每当有来自ConnectionManager的响应时，它会向ItemManager发送通知，然后解析它。

ConnectionManager发布通知，ItemManager正确接收它们。我想用同样的方法来更新我的表格视图。问题出在我的主班上。分析完成后，它不会收到来自ItemManager的通知。

• 的ConnectionManager - >帖子，ItemManager - >接收 - OK
• ItemManager - >帖子，UITableViewController中 - >接收 - NOK

一些代码：

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)") 
    } 
    } 

而且最后我的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！ 我收到通知（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() 
    } 

... 

后注册观察者现在工作得很好:-)