Question

在我的应用程序的注册过程中，我有两个功能 - 首先检查用户输入的句柄以查看它是否已被占用，然后第二个函数设置其余的值：

@IBAction func setupDoneButtonPressed(_ sender: Any) {

    checkHandle()
    setUserInfo()
    self.performSegue(withIdentifier: "setupToChat", sender: nil)
}

checkHandle函数似乎正在做它的工作，因为它检查数据库然后打印“else”条件print语句 - 但是我没有看到警报，程序只是进入应用程序

如果该句柄已被使用，我需要编程停止而不是继续setUserInfo然后进入应用程序。我想在那里显示我的警报，然后允许用户使用不同的句柄再次尝试。

这是checkHandle函数：

func checkHandle() {

    if self.handleTextField.text != nil {
        if let handle = self.handleTextField.text {

            let handleRef: FIRDatabaseReference = FIRDatabase.database().reference().child("users")
            handleRef.queryOrdered(byChild: "handle").queryEqual(toValue: "\(handle)").observeSingleEvent(of: .value, with: { (snapshot) in

                if (snapshot.value is NSNull) {
                    print("handle not in use") // handle not found
                    userRef.child("handle").setValue(handle)
                } else {
                    print("Handle already in use. Value: \(snapshot.value)") // handle is in use
                    let alertController = UIAlertController(title: "Handle Taken", message: "Please choose a different handle", preferredStyle: UIAlertControllerStyle.actionSheet)

                    let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: {(alert :UIAlertAction!) in
                    })
                    alertController.addAction(okAction)

                    self.present(alertController, animated: true, completion: nil)
                }

            })
        }
    }
}

如果已经存在的句柄，我该怎么做才能确保注册过程停止？

Answer 1

你可以这样解决：

首先使checkHandle()成为像checkHandle(completion: @escaping (Bool) -> Void)

那样完成的函数

然后，如果满足completion(true)条件，则在此函数内部调用if，如果不满足，则调用completion(false)。然后在你的按钮处理程序中使用checkHandle()，如下所示：

checkHandle { [weak self] success in 
     guard success else { return }

     self?.setUserInfo()
     self?.performSegue(withIdentifier: "setupToChat", sender: nil)
}

Answer 2

您的代码只是继续处理而不采取任何条件行为。我建议你让checkHandle函数返回一个布尔值，然后做出相应的响应。

func checkHandle(handle: String) -> Bool {
    someBool = // some logic to see if handle exists.
    return someBool 
}

@IBAction func setupDoneButtonPressed(_ sender: Any) {

    if checkHandle() {
        setUserInfo()
        self.performSegue(withIdentifier: "setupToChat", sender: nil)
    } else {
       // present an error, or make suggestions etc
    }
}

Answer 3

@IBAction func setupDoneButtonPressed(_ sender: Any) {

    if checkHandle()
    {
       setUserInfo()
       self.performSegue(withIdentifier: "setupToChat", sender: nil)
    }   
}

func checkHandle() -> Bool {
    let isAvailable = false
    if self.handleTextField.text != nil {
        if let handle = self.handleTextField.text {

            let handleRef: FIRDatabaseReference = FIRDatabase.database().reference().child("users")
            handleRef.queryOrdered(byChild: "handle").queryEqual(toValue: "\(handle)").observeSingleEvent(of: .value, with: { (snapshot) in

                if (snapshot.value is NSNull) {
                    print("handle not in use") // handle not found
                    userRef.child("handle").setValue(handle)
                    isAvailable = true
                } else {
                    print("Handle already in use. Value: \(snapshot.value)") // handle is in use
                    let alertController = UIAlertController(title: "Handle Taken", message: "Please choose a different handle", preferredStyle: UIAlertControllerStyle.actionSheet)

                    let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: {(alert :UIAlertAction!) in
                    })
                    alertController.addAction(okAction)

                    self.present(alertController, animated: true, completion: nil)
                    isAvailable = false
                }

            })
        }
    }
   if isAvailable
   {
      return true
   }
   return false
}

停止程序执行并返回if else条件

3 个答案: