what i am trying to accomplish is once the app is launched it will check for first time use. if it is the first time use it will take you to a view controller to enter credentials, else it will take you to to the main menu of the app. this is what i have so far but every time i launch it will give me a blank page with the error message of "A segue must either have a performHandler or it must override -perform.
" i have both segues linked on storyboard. can any one please steer me in the right direction.
let defaults = UserDefaults.standard
if defaults.string(forKey: "isAppAlreadyLaunchedOnce") != nil{
print("first time")
self.performSegue(withIdentifier: "toToken", sender: nil)
}else{
defaults.set(true, forKey: "isAppAlreadyLaunchedOne")
defaults.synchronize()
print("not first")
self.performSegue(withIdentifier: "toMainMenu", sender: nil)
}
If your segue type is set to be Custom in Storyboard — you have to subclass UIStoryboardSegue with your own logic in order for it to work.
class MySegue: UIStoryboardSegue {
override func perform() {
// your custom transition logic
}
}
Otherwise just use one of the existing presets from iOS SDK.
Your method is very confusing. The way I go about this problem is shown below.
override viewDidLoad() {
super.viewDidLoad
let checkForFirstTimeLaunch = Userdefaults.standard.string(forKey: "Flag")
if checkForFirstTimeLaunch == false {
print("First time launch")
//if user launches app for the first time, it will go here
} else {
//otherwise, it will go here
}
}
Related
This question already has answers here:
Perform Segue on ViewDidLoad
(12 answers)
Closed 4 years ago.
I`m trying to perform a segue if its the first time the app is loading.
I can see my print message in the debugger, but the Perform Segue is not working. I don't get any errors.
Can somebody please tell me whats wrong?
import UIKit
import LocalAuthentication
let isFirstLaunch = UserDefaults.isFirstLaunch()
extension UserDefaults {
// check for is first launch - only true on first invocation after app install, false on all further invocations
// Note: Store this value in AppDelegate if you have multiple places where you are checking for this flag
static func isFirstLaunch() -> Bool {
let hasBeenLaunchedBeforeFlag = "hasBeenLaunchedBeforeFlag"
let isFirstLaunch = !UserDefaults.standard.bool(forKey: hasBeenLaunchedBeforeFlag)
if (isFirstLaunch) {
UserDefaults.standard.set(true, forKey: hasBeenLaunchedBeforeFlag)
UserDefaults.standard.synchronize()
}
return isFirstLaunch
}
}
class loginVC: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
if isFirstLaunch == false {
performSegue(withIdentifier: "setPassword", sender: self)
print("testFalse") }
else {
performSegue(withIdentifier: "setPassword", sender: self)
print("testTrue")}
// Do any additional setup after loading the view, typically from a nib.
}
You can't use performSegue() from within viewDidLoad(). Move it to viewDidAppear().
At viewDidLoad() time, the current view isn't even attached to the window yet, so it's not possible to segue yet.
You can also use a different approach - change the main window's rootViewController to the view controller of your choice depending on isFirstLaunchboolean
UIApplication.shared.keyWindow?.rootViewController = setPasswordViewController
I'm having a problem where every time I enter the right credentials, it brings me to one view controller then opens up the same view controller again even though I only have the login viewer controller linked to one view controller. If I don't enter the right credentials it still brings me into the linked view controller. Here is the code.
EDIT: Using a push segue(show)
#IBAction func loginTapped(_ sender: Any) {
if let Email = userEmail.text, let Pass = userPassword.text{
Auth.auth().signIn(withEmail: Email, password: Pass, completion: { (user, error) in
if error != nil{
print("incorrect")
}
else{
if error == nil{
self.performSegue(withIdentifier: "loginPage", sender: self)
print("correct")
}
}
})
}
}
I don't know if you've fixed your problem, but check your storyboard. Sounds like you have a segue connected from the button to the next ViewController which would result in pressing the button and it'll always push that ViewController.
To do this easily just see if you have a segue connected from the button to your destination ViewController in your MainStoryboard.
In my application, I use UserDefaults to store the user's login status (whether they are logged in or not), and their username. It works fine in that when I login, close the app, and open it again my app skips the login page and recognizes that I am already logged in. Although, I am now trying to install a logout button to a separate viewController. When clicked, this logout button needs to 1.) Reset UserDefaults.loginStatus to "False" 2.) Reset UserDefaults.username to nil 3.) Perform a segue to the login page.
Here is the related code from my ViewController.swift file. This is the first viewController which controls the loginPage.
import UIKit
import Firebase
let defaults = UserDefaults.standard
class ViewController: UIViewController {
func DoLogin(username: String, password: String) {
//I Am not including a lot of the other stuff that takes place in this function, only the part that involves the defaults global variable
defaults.setValue(username, forKey: "username")
defaults.setValue("true", forKey: "loginStatus")
defaults.synchronize()
self.performSegue(withIdentifier: "loginToMain", sender: self) //This takes them to the main page of the app
}
override func viewDidLoad() {
super.viewDidLoad()
if let stringOne = defaults.string(forKey: "loginStatus") {
if stringOne == "true" { //If the user is logged in, proceed to main screen
DispatchQueue.main.async
{
self.performSegue(withIdentifier: "loginToMain", sender: self)
}
}
}
}
Below is my code in SecondViewController.swift, particularly the logout function.
import UIKit
import Firebase
class SecondViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
if let username = defaults.string(forKey: "username") {
checkAppSetup(username: username) //This is an unrelated function
//I included this because this works fine. Proving that I am able to read the defaults variable fine from this other viewController
}
}
#IBAction func logout(_ sender: Any) {
defaults.setValue("false", forKey: "username")
defaults.setValue("false", forKey: "loginStatus")
defaults.synchronize()
performSegue(withIdentifier: "logoutSegue", sender: nil)
}
When the logout function is run, the segue performs fine but the default values do not change. Can someone explain why and what I can do to get around this?
**Side note, I am not actually going to set the defaults to "false" and "false". That is just temporary for while I am debugging this issue.
Several things.
You should be using set(_:forKey:) and object(_:forKey) to read and write key/value pairs to defaults, not setValue(_:forKey). (Your use of defaults.string(forKey: "loginStatus") is correct, however.)
You should probably be writing a nil to the userName key:
defaults.set(nil, forKey: "username")
And your logout IBAction should almost certainly be setting loginStatus to false, not true.
Try changing those things.
Also, there is no reason to call synchronize unless you are terminating your app in Xcode rather than pressing the home button on the device/simulator in order to let it exit normally.
Hey i used the exactly same concept recently :
1) In your initial view, in the viewDidLoad() , check whether somebody is already logged in or not, and only one user can be logged in one device at a time, so we check like
let defaults = UserDefaults.standard
if defaults.object(forKey: "userName") != nil && defaults.object(forKey: "userPassword") != nil
{
let loginObject = self.storyboard?.instantiateViewController(withIdentifier: "YourSecondViewController") as! YourSecondViewController
//As someone's details are already saved so we auto-login and move to second view
}}
2) In your sign in button function , check whatever condition you want to check and then, inside the same, if condition satisfies then save data to userDefaults.
// If no details are saved in defaults, then control will come to this part, where we will save the entered userName and Password
let defaults = UserDefaults.standard
defaults.set(self.enteredUseName, forKey: "userName")
defaults.set(self.enteredPassword, forKey: "Password")
defaults.synchronize()
3) On logout button , delete the userDefaults and load the login view again :
let defaults = UserDefaults.standard
defaults.removeObject(forKey: "userName") //We Will delete the userDefaults
defaults.removeObject(forKey: "userPassword")
defaults.synchronize() //Sync. the defaults.
navigationController?.popToRootViewController(animated: true) //Move Back to initial view.
4) If you are using a navigation control, that you must be using :P then you will surely see the back button which will open the second view if clicked, for that you can hide the navigation bar in viewDidLoad() of your login view
self.navigationController?.navigationBar.isHidden = true
I want to show a tutorial that is a UIPageView only once at the beginning of the first launch.
I am attempting this using this code
let launchedBefore = UserDefaults.standard.bool(forKey: "launchedBefore")
if launchedBefore {
performSegue(withIdentifier: "tutorialtohome1", sender: nil)
}
else {
UserDefaults.standard.set(true, forKey: "launchedBefore")
}
For some reason it's not working with the UIPageController, it works fine with other views.
Just to make clear, I only want this view to appear once, then never again, as it acts as a tutorial.
Any suggestions?
Thanks
You need to check the OBJECT. Not the bool. This is better way to do it. On first run, there are no such key "lauchedBefore". You cannot check boolean value of what's not there.
let launchedBefore = UserDefaults.standard.object(forKey: "launchedBefore")
if (launchedBefore==nil) {
performSegue(withIdentifier: "tutorialtohome1", sender: nil)
UserDefaults.standard.set(true, forKey: "launchedBefore")
}
else {
// already launched, so do nothing.
}
I am trying to switch view controllers after a user successfully logs in to their account, but it is not working correctly. I cant use a segue directly because if the login button is clicked it will go to that view controller regardless if the information is correct or not. I have tried everything that I know of with no success. This is the code I am trying.
#IBAction func loginTapped(sender: AnyObject) {
let username = usernameField.text
let password = passwordField.text
if username.isEmpty || password.isEmpty {
var emptyFieldsError:UIAlertView = UIAlertView(title: "Please try again", message: "Please fill in all the fields we can get you logged in to your account.", delegate: self, cancelButtonTitle: "Try again")
emptyFieldsError.show()
}
PFUser.logInWithUsernameInBackground(username, password:password) {
(user: PFUser?, error: NSError?) -> Void in
if user != nil {
self.performSegueWithIdentifier("Klikur", sender: self)
} else {
if let errorString = error!.userInfo?["error"] as? String {
self.errorMessage = errorString
}
self.alertView("Please try again", message: "The username password combiation you have given us does not match our records, please try again.", buttonName: "Try again")
}
}
}
I have the storyboard ID set to "Test" and it is not switching view controller when the correct information is entered. Can somebody help me resolve my problem?
[Assuming that your code is not crashing, but rather just failing to segue]
At least one problem is:
self.performSegueWithIdentifier("Test", sender: self)
should be:
dispatch_async(dispatch_get_main_queue()) {
[unowned self] in
self.performSegueWithIdentifier("Test", sender: self)
}
Remember that all UI operations must be performed on the main thread's queue. You can prove to yourself you're on the wrong thread by checking:
NSThread.isMainThread() // is going to be false in the PF completion handler
ADDENDUM
If there's any chance self might become nil, such as getting dismissed or otherwise deallocated because it's not needed, you should capture self weakly as [weak self] not unowned, and use safe unwrapping: if let s = self { s.doStuff() } or optional chaining: self?.doStuff(...)
ADDENDUM 2
This seems to be a popular answer so it's important to mention this newer alternative here:
NSOperationQueue.mainQueue().addOperationWithBlock {
[weak self] in
self?.performSegueWithIdentifier("Test", sender: self)
}
Note, from https://www.raywenderlich.com/76341/use-nsoperation-nsoperationqueue-swift:
NSOperation vs. Grand Central Dispatch (GCD)
GCD [dispatch_* calls] is a lightweight way to represent units of work that are going to be executed concurrently.
NSOperation adds a little extra overhead compared to GCD, but you can add dependency among various operations and re-use, cancel or suspend them.
ADDENDUM 3
Apple hides the single-threaded rule here:
NOTE
For the most part, use UIKit classes only from your app’s main thread.
This is particularly true for classes derived from UIResponder or that
involve manipulating your app’s user interface in any way.
SWIFT 4
DispatchQueue.main.async(){
self.performSegue(withIdentifier: "Test", sender: self)
}
Reference:
https://developer.apple.com/documentation/uikit
Make sure you're putting your:
self.performSegue(withIdentifier: ..., ...)
in viewDidAppear or later. It won't work in viewWillAppear or viewDidLoad.
I've got the same problem with login issue. probably we do the same tutorial. After naming your segue identifier you need to replace:
performSegueWithIdentifier("Klikur", sender: self)
with:
dispatch_async(dispatch_get_main_queue()){
self.performSegueWithIdentifier("Klikur", sender: self)
}
type of seque needs to be set as "show (e.g. Push)" in the storyboard segue.
Hope it will work.
The segue identifier that you pass to performSegueWithIdentifier(_:sender:) must exactly match the ID you've given the segue in the storyboard. I assume that you have a segue between the login view controller and the success view controller, which is as it should be; if not, ctrl+drag from the first to the second view controller, then select the segue's icon in the storyboard and set its ID to Klikur. Don't perform the navigation on the button click, as one commenter said, because that defeats the main purpose of having segues, which is to give a visual indication of the application flow in the storyboard.
EDIT: Here's the code for a login view controller:
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var usernameField: UITextField!
#IBOutlet weak var passwordField: UITextField!
#IBAction func attemptLogin(sender: AnyObject) {
if !usernameField!.text!.isEmpty && !passwordField!.text!.isEmpty {
performSegueWithIdentifier("Klikur", sender: self)
}
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if "Klikur" == segue.identifier {
// Nothing really to do here, since it won't be fired unless
// shouldPerformSegueWithIdentifier() says it's ok. In a real app,
// this is where you'd pass data to the success view controller.
}
}
}
And a screenshot of the segue properties that I'm talking about:
swift 3.x
DispatchQueue.main.async(){
self.performSegue(withIdentifier: "Klikur", sender: self)
}
DispatchQueue.main.async() {
self.performSegue(withIdentifier: "GoToHomeFromSplash", sender: self)`
}
Check to make sure you are running the perform segue on a visible view controller.
This is an edge case, but my perform segue failed when I attempted to run it on the view controller belonging to my UIPageViewController that was not currently visible. It also failed if I attempted to do the segue on all view controllers belonging to my UIPageViewController, including the view controller currently visible. The fix was to track which view controller was currently visible in my UIPageViewController, and only perform the segue on that view controller.
An example in a login. When you have success in your login after clicking a button (Action) you can use:
self.performSegue(withIdentifier: "loginSucess", sender: nil)
But if you are launching the app and you got the credentials from your keychain you need to use this as a part of the theard:
DispatchQueue.main.async(){
self.performSegue(withIdentifier: "sessionSuccess", sender: nil)
}