ios - 为什么我的 firebase 数据库不等待更新值

Question

所以我真的是线程的新手，而且我一整天都在阅读它。出于某种原因，虽然在其他代码执行之前数据没有加载

基本上，我需要将所有具有键 ["whatever"] 的值填充到一个数组中，这在其他地方有效，因为我不需要先加载它。所以我已经检查并仔细检查了我正在更新的 key 确实存在，我正在提取的 key 确实存在，可能还没有值，但 key 确实存在。

问题是代码会快速通过该方法。我如何让主线程等到我的 firebase 加载了我在下面尝试过的数据，但它似乎没有工作

这是我的代码

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let alertController = UIAlertController(title: "Accept Bet", message: "Match the bet of " + amountBets[indexPath.row], preferredStyle: .alert)

    let okButton = UIAlertAction(title: "No", style: .default, handler: { (action) -> Void in
        print("Ok button tapped")
    })

    let yesButton = UIAlertAction(title: "Yes", style: .default, handler: { (action) -> Void in
        // let them know to wait a second or the bet won't go through
        var waitController = UIAlertController(title: "Please Wait", message: "You must wait for the bet to go through", preferredStyle: .alert)

        self.present(waitController, animated: true, completion: nil)
        //take away that bitches money
        self.takeAwayMoney(self.amountBets[indexPath.row], completion: { (result: Bool?) in

            guard let boolResult = result else {
                return
            }

            if boolResult == true {
                self.updateBet(indexPath.row, completion: {(result: String?) in





                    guard let resultRecieved = result else {
                        return
                    }
                    print(self.opposingUserNames)
                    //let delayInSeconds = 7.0 // 1
                    //DispatchQueue.main.asyncAfter(deadline: .now() + delayInSeconds) { // 2
                    self.dismiss(animated: true, completion: nil)
                    let successController = UIAlertController(title: "Success", message: "You have made a bet with " + self.opposingUserNames!, preferredStyle: .alert)
                    let okButt = UIAlertAction(title: "Ok", style: .default, handler: nil)
                    successController.addAction(okButt)
                    self.present(successController, animated: true, completion: nil)
                    //lastly delete the opposing UserName
                    print(self.opposingUserNames)
                    self.amountBets.remove(at: indexPath.row)
                    self.tableView.reloadData()
                    print("Second")
                    print(self.opposingUserNames)
                    //}

                })
            } else {
                return
            }

        })

        //then delete that cell and do another pop up that says successful
        // check if value is yes or no in the database


    })

    alertController.addAction(okButton)
    alertController.addAction(yesButton)
    present(alertController, animated: true, completion: nil)
}

下面的函数更新值 OpposingUsername 并显示

func updateBet(_ index: Int, completion: @escaping (_ something: String?) -> Void) {
    let userID = FIRAuth.auth()?.currentUser?.uid
    datRef.child("User").child(userID!).observeSingleEvent(of: .value, with: { (snapshot) in
        // Get user value
        let value = snapshot.value as? NSDictionary
        // ...


        self.datRef.child("Bets").observe(.childAdded, with: { snapshot in
            //
            // this is the unique identifier of the bet.  eg, -Kfx81GvUxoHpmmMwJ9P
            guard let dict = snapshot.value as? [String: AnyHashable] else {
                print("failed to get dictionary from Bets.\(self.userName)")
                return
            }
            let values = ["OpposingUsername": self.userName,"Show": "no"]


            self.datRef.child("Bets").child(self.tieBetToUser[index]).updateChildValues(values)
            // now get the opposing username which is just the Username registered to that specific bet
            self.datRef.child("Bets").child(self.tieBetToUser[index]).observe(.childAdded, with: { snapshot in
                guard let dict2 = snapshot.value as? [String: AnyHashable] else {
                    return
                }
                let userNameOfOtherPlayer = dict2["Username"] as? String
                self.opposingUserNames = userNameOfOtherPlayer!
                completion(self.opposingUserNames)
            })


        })

    }) { (error) in
        print(error.localizedDescription)
    }


}

好的，使用这个更新后的代码，它消除了我之前遇到的逻辑错误，但现在该应用程序卡在我的 waitAlertViewController 上。不知道为什么。它确实更新了 firebase 数据库中的赌注，所以我知道它的工作和运行该代码，但它就像从未完成这一切。抱歉，bibscy，我现在明白你的意思了

完成处理程序一旦你更好地理解它们就会非常强大

Answer 1

 //Notice that I made `result: String?` optional, it may or may not have a value.    
 func getOpoosingUserNames(_ username: String,_ index: Int, completion: @escaping (_ result: String?) -> Void ) {
    let userID = FIRAuth.auth()?.currentUser?.uid
    datRef.child("User").child(userID!).observeSingleEvent(of: .value, with: { (snapshot) in
        // Get user value
        let value = snapshot.value as? NSDictionary
        let username = value?["username"] as? String ?? ""
        self.userName = username

        // ...


        self.datRef.child("Bets").observe(.childAdded, with: { snapshot in
            //
            // this is the unique identifier of the bet.  eg, -Kfx81GvUxoHpmmMwJ9P

            let betId = snapshot.key as String
            guard let dict = snapshot.value as? [String: AnyHashable] else {
                print("failed to get dictionary from Bets.\(self.userName)")
                return
            }
            if let show = dict["Show"] as? String {

                let opposingUser = dict["OpposingUsername"] as? String
                    self.opposingUserNames.append(opposingUser!)
            }



             completion(opposingUserNames)
        })
    }) { (error) in
        print(error.localizedDescription)
    }

}



    //update the be
   func updateBet(_ index: Int, completion: @escaping (_ something: [String]?) -> Void) {
  let userID = FIRAuth.auth()?.currentUser?.uid
datRef.child("User").child(userID!).observeSingleEvent(of: .value, with: { (snapshot) in
    // Get user value
     let value = snapshot.value as? NSDictionary
    // ...


     self.datRef.child("Bets").observe(.childAdded, with: { snapshot in
        //
        // this is the unique identifier of the bet.  eg, -Kfx81GvUxoHpmmMwJ9P
        guard let dict = snapshot.value as? [String: AnyHashable] else {
            print("failed to get dictionary from Bets.\(self.userName)")
            return
        }
         let values = ["OpposingUsername": self.userName,"Show": "no"]

    //store the values received from Firebase in let valueOfUpdate and pass this
  // constant to your completion handler completion(valueOfUpdate) so that you can use this value in func 
   //tableView(_ tableView:_, didSelectRowAt indexPath:_)
          let valueOfUpdate =  self.datRef.child("Bets").child(self.tieBetToUser[index]).updateChildValues(values)



     completion(valueOfUpdate)
  }) { (error) in
    print(error.localizedDescription)
  }


}


  func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let alertController = UIAlertController(title: "Accept Bet", message: "Match the bet of " + amountBets[indexPath.row], preferredStyle: .alert)

    let okButton = UIAlertAction(title: "No", style: .default, handler: { (action) -> Void in
        print("Ok button tapped")
    })

    let yesButton = UIAlertAction(title: "Yes", style: .default, handler: { (action) -> Void in
        //take away that bitches money
        self.takeAwayMoney(self.amountBets[indexPath.row])

        //then delete that cell and do another pop up that says successful
        // check if value is yes or no in the database
        self.updateBet(indexPath.row, completion: {(result: String) in


  guard let resultReceivedInupdateBet = result, else {
    print("result of updateBet() is \(result)")
}
         print("If you see this print, database was updated")

  //calling this method with the indexPath.row clicked by the user
     self.getOpoosingUserNames(self.userName, indexPath.row, completion: { (result: [String]) in


 guard let resultReceivedIngetOpoosingUserNames = result{
      print("result of getOpoosingUserNames is \(result)")
 }
     print("If you see this print, you received a value from db after calling getOpoosingUserNames and that value is in \(result) ")

  //result is not nil, resultReceivedIngetOpoosingUserNames has the same value as result.

 }//end of self.getOpoosingUserNames

        self.checkForNo(indexPath.row)
        self.amountBets.remove(at: indexPath.row)
        self.tableView.reloadData()
        print(self.opposingUserNames)

        let successController = UIAlertController(title: "Success", message: "You have made a bet with " + self.opposingUserNames[indexPath.row], preferredStyle: .alert)
        let okButt = UIAlertAction(title: "Ok", style: .default, handler: nil)
        successController.addAction(okButt)
        self.present(successController, animated: true, completion: nil)
        //lastly delete the opposing UserName
        self.opposingUserNames.remove(at: indexPath.row)

    })

    alertController.addAction(okButton)
    alertController.addAction(yesButton)
    present(alertController, animated: true, completion: nil)
 }