问题
I have defined an alertcontroller when username or password is not correct the alert should pop, and it is working fine. but when the username & password is matched despite matching it pops up everytime when log in. I think I have not defined nested condition in a right way? help me to sort the multiple nested condition.
Code for Login
import UIKit
import CoreData
import Foundation
class ViewController: UIViewController {
var usernameGlobal : String = ""
@IBOutlet weak var emailText: UITextField!
@IBOutlet weak var passText: UITextField!
@IBOutlet weak var loginButton: UIButton!
@IBAction func loginAction(_ sender: Any) {
let appDel = UIApplication.shared.delegate as! AppDelegate
let context = appDel.persistentContainer.viewContext
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")
request.returnsObjectsAsFaults = false
// request.predicate = NSPredicate(format: "username = %@", "" + emailText.text!)
do {
let results = try! context.fetch(request)
if(results.count > 0){
for result in results as! [NSManagedObject]
{
if emailText.text == result.value(forKey: "username") as? String && passText.text == result.value(forKey: "password") as? String {
print(emailText.text!, passText.text!)
usernameGlobal = self.emailText.text!
let mainStoryBoard: UIStoryboard = UIStoryboard(name: "Main", bundle : nil)
let desController = mainStoryBoard.instantiateViewController(withIdentifier: "AddViewController") as! AddViewController
let newFrontViewController = UINavigationController.init(rootViewController:desController)
revealViewController().pushFrontViewController(newFrontViewController, animated: true)
}
else {
let alertController = UIAlertController(title: "Oops!", message: "Incorrect username or password", preferredStyle: .alert)
let defaultAction = UIAlertAction(title: "OK", style: .default, handler: nil)
alertController.addAction(defaultAction)
present(alertController, animated: true, completion: nil)
}
}
}
}
}
@IBAction func signupSegue(_ sender: Any) {
let mainStoryBoard: UIStoryboard = UIStoryboard(name: "Main", bundle : nil)
let desController = mainStoryBoard.instantiateViewController(withIdentifier: "SignupViewController") as! SignupViewController
let newFrontViewController = UINavigationController.init(rootViewController:desController)
revealViewController().pushFrontViewController(newFrontViewController, animated: true)
}
override func viewDidLoad() {
super.viewDidLoad()
loginButton.backgroundColor = UIColor.blue
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
回答1:
You can use this code:
@IBAction func loginAction(_ sender: Any) {
let appDel = UIApplication.shared.delegate as! AppDelegate
let context = appDel.persistentContainer.viewContext
let isMatched = false
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")
request.returnsObjectsAsFaults = false
do {
let results = try! context.fetch(request)
if(results.count > 0){
for result in results as! [NSManagedObject]
{
if emailText.text == result.value(forKey: "username") as? String && passText.text == result.value(forKey: "password") as? String {
print(emailText.text!, passText.text!)
usernameGlobal = self.emailText.text!
let mainStoryBoard: UIStoryboard = UIStoryboard(name: "Main", bundle : nil)
let desController = mainStoryBoard.instantiateViewController(withIdentifier: "AddViewController") as! AddViewController
let newFrontViewController = UINavigationController.init(rootViewController:desController)
revealViewController().pushFrontViewController(newFrontViewController, animated: true)
isMatched = true
break
}
}
if !isMatched {
let alertController = UIAlertController(title: "Oops!", message: "Incorrect username or password", preferredStyle: .alert)
let defaultAction = UIAlertAction(title: "OK", style: .default, handler: nil)
alertController.addAction(defaultAction)
present(alertController, animated: true, completion: nil)
}
}
}
}
Changes:
You add
let isMatched = false
You add break statement in if condition. So that it breaks the loop once username and password is matched. Then after for loop check if the isMatched is false, then show the result.
回答2:
if your result contains multiple different element then else block will execute multiple time. thats why alert appeared multiple time . when you found a match then you should return . if no match found then after loop alert will appear for one time .
Use this:
@IBAction func loginAction(_ sender: Any) {
let appDel = UIApplication.shared.delegate as! AppDelegate
let context = appDel.persistentContainer.viewContext
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")
request.returnsObjectsAsFaults = false
// request.predicate = NSPredicate(format: "username = %@", "" + emailText.text!)
do {
let results = try! context.fetch(request)
if(results.count > 0){
for result in results as! [NSManagedObject]
{
if emailText.text == result.value(forKey: "username") as? String && passText.text == result.value(forKey: "password") as? String {
print(emailText.text!, passText.text!)
usernameGlobal = self.emailText.text!
let mainStoryBoard: UIStoryboard = UIStoryboard(name: "Main", bundle : nil)
let desController = mainStoryBoard.instantiateViewController(withIdentifier: "AddViewController") as! AddViewController
let newFrontViewController = UINavigationController.init(rootViewController:desController)
revealViewController().pushFrontViewController(newFrontViewController, animated: true)
return
}
}
let alertController = UIAlertController(title: "Oops!", message: "Incorrect username or password", preferredStyle: .alert)
let defaultAction = UIAlertAction(title: "OK", style: .default, handler: nil)
alertController.addAction(defaultAction)
present(alertController, animated: true, completion: nil)
}
}
}
来源：https://stackoverflow.com/questions/47881304/alertcontroller-is-being-popped-every-time-in-nested-conditions-swift-ios