ios - 从 Firebase 解析数据时无法成功重新加载 UITableView 元素

Question

我正在制作一个应用程序，用户可以在其中买卖门票。用户可以创建新票证并成功上传到 Firebase，但是对票证 ID 的引用存储在用户数据中，该用户数据引用票证数据中的票证 ID。数据库结构如下:

数据库

• 用户
• 门票

门票

• 门票信息

用户

• 他们正在销售的门票的用户信息和门票 ID

我的问题是，第一次从售票处加载门票时一切都很好。但是，当用户添加他们正在销售的新门票时， TableView 会加载所有内容两次。

override func viewWillAppear(_ animated: Bool) {
    self.tickets = []
    DataService.ds.REF_USER_CURRENT.child("selling").observe(.value, with: { (snapshot) in //HERE WE REFERNCE OUR SINGELTON CLASS AND OBSERVE CHAMGE TO THE POSTS OBJECT
        self.tickets = [] //WE CLEAR THE POSTS ARRAY BEFORE WE START MANIPULATION TO MAKE SURE THAT WE DONT REPEAT CELLS
        if let snapshot = snapshot.children.allObjects as? [DataSnapshot]{
            print("ADAM: \(snapshot)")//CHECKING THAT THE OBJECTS EXIST AS AN ARRAY OF DATA SNAPSHOTS
            for snap in snapshot {
                DataService.ds.REF_TICKETS.child(snap.key).observe(.value, with: { (snapshot) in

                    if let ticketDict = snapshot.value as? Dictionary<String, AnyObject>{

                        let ticket = Ticket(ticketID: snap.key, ticketData: ticketDict)

                        self.self.tickets.append(ticket)
                    }

                    self.sell_ticketsTableView.reloadData()
                })
            }

        }
        //self.sell_ticketsTableView.reloadData()
        self.tickets = []//RELAOD THE DATA
    })
}

我不太确定我哪里出了问题。

Answer 1

请将您的代码更改为此。我添加了清除数组的部分

  override func viewWillAppear(_ animated: Bool) {
        self.removeAll() // This is how you clear your array
        DataService.ds.REF_USER_CURRENT.child("selling").observe(.value, with: { (snapshot) in //HERE WE REFERNCE OUR SINGELTON CLASS AND OBSERVE CHAMGE TO THE POSTS OBJECT
            self.tickets = [] //WE CLEAR THE POSTS ARRAY BEFORE WE START MANIPULATION TO MAKE SURE THAT WE DONT REPEAT CELLS
            if let snapshot = snapshot.children.allObjects as? [DataSnapshot]{
                print("ADAM: \(snapshot)")//CHECKING THAT THE OBJECTS EXIST AS AN ARRAY OF DATA SNAPSHOTS
                for snap in snapshot {
                    DataService.ds.REF_TICKETS.child(snap.key).observe(.value, with: { (snapshot) in

                        if let ticketDict = snapshot.value as? Dictionary<String, AnyObject>{

                            let ticket = Ticket(ticketID: snap.key, ticketData: ticketDict)

                            self.tickets.append(ticket)
                        }

                        self.sell_ticketsTableView.reloadData()
                    })
                }

            }
            //self.sell_ticketsTableView.reloadData()
        })
    }