I've tried passing data backward from my unwind segue in a number of ways. It seems like the data is not getting sent or its getting sent after viewDidLoad() so the label I'm trying to set isn't getting updated. The unwind segue is working, and below I use prepare for segue with some success to change the title of the previous view controller to 'new title', but the last line isn't setting nbaRotoHome.player to 'new player name'.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "BuyStatsTapPager" {
let nav = segue.destination as! UINavigationController
let buyStatsTapPager = nav.viewControllers[0] as! BuyStatsTabPager
buyStatsTapPager.selectedPlayerBuyStats = selectedPlayer
buyStatsTapPager.buyStatsRef = self
}
if segue.identifier == "unwindToViewController1" {
var viewControllers: [UIViewController] = mainNavigationController.viewControllers as [UIViewController];
if(viewControllers.count == 3){
viewControllers.remove(at: viewControllers.count-2)
mainNavigationController?.viewControllers = viewControllers
}
let enteredContestViewController = viewControllers[viewControllers.count-1]
enteredContestViewController.title = "new title"
self.presentingViewController?.dismiss(animated: true, completion: nil)
let nbaRotoHome = segue.destination as! NBARotoHome
nbaRotoHome.player = "new player name"
}
Back in my previous view controller I have
#IBAction func prepareForUnwind(segue: UIStoryboardSegue) {
}
And after looking at this question
Passing data with unwind segue
I've also tried getting the data this way in the previous view controller
#IBAction func prepareForUnwind(segue: UIStoryboardSegue) {
if let sourceViewController = segue as? BuyStats {
playerNameLabel.text = sourceViewController.playerName
}
}
If I need to add more detail to what I'm trying to do please ask and I will edit. I wanted to ask the question but I am having trouble formulating.
It seems like the data is not getting sent or its getting sent after viewDidLoad() so the label I'm trying to set isn't getting updated.
In an unwind segue you are returning to an already created viewController, so viewDidLoad happened ages ago before you segued to the other viewController.
If you're using segues, you should not be mucking with the array of viewControllers in the navigationController or calling dismiss. The unwind segue will do all of that. Just get the destination in prepare(for:sender:) and set the data:
if segue.identifier == "unwindToViewController1" {
let nbaRotoHome = segue.destination as! NBARotoHome
nbaRotoHome.player = "new player name"
}
or in your prepareForUnwind get the source and read the data:
In this line you are missing .source. Change:
if let sourceViewController = segue as? BuyStats
to:
if let sourceViewController = segue.source as? BuyStats
Related
I'm learning swift from couple months and one thing I keep screwing up is passing data between ViewControllers. When I PO the path of the forward looking variable from within the prepareForSegue method, the value is intact. But when the new ViewController actually appears and I checked its value, it is nil at that point. if anyone could point me in the right direction I'd be very appreciative.
class LoginViewController: UIViewController {
var user_ID:String = ""
//this below is within another method activated by button
Auth.auth().signIn(withEmail: email, password: password) { (result, error) in
if error != nil {
print ("there was an error signing in")
print (error!.localizedDescription)
return
}
else {
//go to home screen
let userUID = result?.user.uid
print (userUID)
self.user_ID = userUID
self.performSegue(withIdentifier: "MainSegue", sender: self)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
//this is the destination VC
let viewController = segue.destination as! ViewController
viewController.user_ID = self.user_ID
//NOTE: if I break here and PO viewConroller.user_ID the value is intact
let homeViewController = (self.storyboard?.instantiateViewController(withIdentifier: "MainVC"))! as! ViewController
//let mainViewController = ViewController()
//mainViewController.user_ID = userUID
self.present(homeViewController, animated: true, completion: nil)
}
class ViewController: UIViewController {
var persons = [Person]()
let db = Firestore.firestore()
var user_ID:String = ""
//NOTE: WHEN `viewdidload` runs value of user_ID is nil
Phillip in the comments above provided the solution. The present ViewController was the problem. The segue already does that. Thank you!!!
When I read the QR code, I want to open the viewcontroller with the webview. But I get the error in the title. Even though I have made the relationship between Viewcontroller and defined it, I still get this error. I defined it in web_load, but it still looks undefined.
func launchApp(decodedURL: String) {
if let url = URL(string: decodedURL) {
if UIApplication.shared.canOpenURL(url) {
// UIApplication.shared.open(url)
self.performSegue(withIdentifier: "web_load", sender: nil)
}
}
}) }
override func prepare(for segue: UIStoryboardSegue, sender: Any?){
if segue.identifier == "web_load"{
if let nextVC = segue.destination as? DetailsViewController {
nextVC.scannedCode = messageLabel.text
}
}
}
Make sure you have set "web_load" as a storyboard ID not as an identifier.
Follow this step
select the segue arrow -> got to attribute inspector -> identifier(web_load)
like this:
webload is segue identifier so that you can not set on viewController Storyboard ID you need to set as per given below screenshot.
Storyboard ID in need to set Your ViewController name.
Click on segue and set identifier as web_load then it can work properly.
I have a collection view with some cells representing a contact (their data has a phone number and name) and I am trying to add the contact to the iPhone contacts. I have created a segue from a button called "add contact" that is inside the CollectionViewCell to a navigation controller, and set its identifier as "ADD_CONTACT".
In the storyboard, my segue has a navigation controller with no root view controller.
in prepareToSegue of the view controller that delegates my UICollectionView I wrote this code:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == ADD_CONTACT {
let dest = segue.destination as! UINavigationController
if let cell = sender as? SBInstructionCell {
if cell.isContact {
let newContact = CNMutableContact()
if let phone = cell.instructionBean?.contactAttachment?.phoneNumber{
newContact.phoneNumbers.append(CNLabeledValue(label: "home", value: CNPhoneNumber(stringValue: phone)))
}
if let name = cell.instructionBean?.contactAttachment?.contactName {
newContact.givenName.append(name)
}
let contactVC = CNContactViewController(forNewContact: newContact)
contactVC.contactStore = CNContactStore()
contactVC.delegate = self
dest.setViewControllers([contactVC], animated: false)
}
}
}
}
this results with a black screen.
How can this be fixed? I want to see the CNContactViewController
Eventually I solved this in a different approach using Closures.
In my UICollectionViewCell
I added this var:
var closureForContact: (()->())? = nil
Now on my button's action in the same cell I have this func:
#IBAction func addContactTapped(_ sender: UIButton) {
if closureForContact != nil{
closureForContact!()
}
}
Which calls the function.
In my CollectionView in cell for item at index path, I set the closure like this:
cell.closureForContact = {
if cell.isContact {
let newContact = CNMutableContact()
if let phone = cell.instructionBean?.contactAttachment?.phoneNumber{
newContact.phoneNumbers.append(CNLabeledValue(label: "home", value: CNPhoneNumber(stringValue: phone)))
}
if let name = cell.instructionBean?.contactAttachment?.contactName {
newContact.givenName.append(name)
}
let contactVC = CNContactViewController(forNewContact: newContact)
contactVC.contactStore = CNContactStore()
contactVC.delegate = self
contactVC.allowsEditing = true
contactVC.allowsActions = true
if let nav = self.navigationController {
nav.navigationBar.isTranslucent = false
nav.pushViewController(contactVC, animated: true)
}
}
}
This worked perfectly. I learned that for navigating from a cell, it is best to use closures.
I currently have a navigation controller setup like this:
and my prepareForSegue, that passes data between the initial view (Login View Controller) and the Navigation controller looks like such:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
super.prepareForSegue(segue, sender: sender)
let navVc = segue.destinationViewController as! UINavigationController // 1
let chatVc = navVc.viewControllers.first as! ChatViewController // 2
chatVc.senderId = userID // 3
chatVc.senderDisplayName = "" // 4
}
However, when I try to embed in a Tab Bar controller (to add more pages/functionality to my app) like this...
...and run my application, my program crashes at the line let navVc = segue.destinationViewController as! UINavigationController
I know that the problem is that after my initial view, it goes to the tab bar which is type UITabBarController rather than UINavigationController however if I change it, my data does not go to the view that I want it to go to...it is kind of confusing.
Please let me know if you have any ideas how to implement this, or if you have any questions feel free to ask me for clarification.
Thanks!
P.s. The error that I am receiving in the console is:
Could not cast value of type 'UITabBarController' (0x10b8e48b0) to 'UINavigationController' (0x10b8e4860).
Try this:
Start by casting destinationViewController to UITabBarController and then using the viewControllers property to access the first viewController in the tabBarController:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let tabVc = segue.destinationViewController as! UITabBarController
let navVc = tabVc.viewControllers!.first as! UINavigationController
let chatVc = navVc.viewControllers.first as! ChatViewController
chatVc.senderId = userID
chatVc.senderDisplayName = ""
}
In the CS193p class, Paul Hegarty shows the uses of extensions to deal with Navigation Controller segues (Lecture 8: 23'). The UIViewController extension introduces a new computed property: contentViewController available to all UIViewControllers (and subclasses).
The code I posted below was adapted to work with TabBarViewControllers as well.
When you are attempting to cast your navigation controller as your ChatViewController, the segue.destinationController.contentViewController will recursively return the ChatViewController.
class LoginViewController: UIViewController {
/* ... */
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let chatVc = segue.destinationViewController.contentViewController as? ChatViewController {
chatVc.senderId = userID
chatVc.senderDisplayName = ""
}
}
}
extension UIViewController {
var contentViewController: UIViewController {
if let navcon = self as? UINavigationController {
return navcon.visibleViewController ?? self
} else if let tabcon = self as? UITabBarController {
return tabcon.selectedViewController ?? self
} else {
return self
}
}
}
A clean way of doing this would be that right after you log in, you use something like:
let controller = self.storyboard?.instantiateViewControllerWithIdentifier("setthisisyourstoryboard") as! UITabBarController // This would instantiate the TabBarController.
let navInstance = controller[0] as! UINavigationController // This would instantiate the navigationController, that is placed at 0th index in the array of all view controllers that are child to TabBarController, since you only have one child, you can use 0 as index
if navInstance.viewControllers[0] is YourClassName { // YouClassName is the name of the class right next to the navigation view controller, and it is also the only child of navigation Controller(0 index)
// You can also send some data here (for example the sender id)
(navInstance.viewControllers[0] as! YourClassName).someProperty = Value
}
// This line would present the tabBar controller, that would ultimately reach the end of the stack. I have used this approach in many apps, it works great!
self.presentViewController(controller, animated: true, completion: nil)
You can delete the segue after this and set storyboard id for the tabbarcontroller.
I like to do it this way because it is more natural. What I mean is the UITabBarController is mostly a parent to View Controllers, I don't like the idea of setting a UITabBarController as a child to UIView Controller.
Maybe there is nothing wrong with it, but I don't prefer it.
Here. it's working pretty fine for me:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let tabVC = segue.destination as? UITabBarController {
if let navVC = tabVC.viewControllers!.first as? UINavigationController {
if let nextVC = navVC.viewControllers.first as? NextVC {
nextVC.varName = "works like a charm"
}
}
}
}
NextVC is your target VC which you want to send your variable into.
I have a UITableView that uses an NSFetchedResultsController to fetch my data for the UITableView. When a user selects a row in the UITableView, I have an edit modal view slide up with two UITextFields for the user to edit the data that was in the UITableViewCell. What I am trying to accomplish is setting the text of each UITextField with the text that was in the UITableViewCell from Core data. I am doing this so that the user does not have to re-type their data just to make an edit.
The issue is when I try to set the text for each UITextField in prepareForSegue, I am getting a fatal error " unexpectedly found nil while unwrapping an Optional value". I know that the data is there, so I am unsure exactly why it is finding nil. I followed this stackoverflow post to write my prepareForSegue function correctly when using an NSFetchedResultsController. This is my code:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "edit" {
if let inputController = segue.destinationViewController as? QAInputViewController {
let uri = currentDeck!.objectID.URIRepresentation()
let objectID = managedContext.persistentStoreCoordinator?.managedObjectIDForURIRepresentation(uri)
inputController.currentDeck = managedContext.objectWithID(objectID!) as? Deck
if let indexPath = tableView.indexPathForCell(sender as! DisplayTableViewCell) {
let data = fetchedResultsController.objectAtIndexPath(indexPath) as? Card
inputController.questionInput.text = data?.question
inputController.answerInput.text = data?.answer
}
}
}
}
Thank you for your help.
I found that my the crash was happening because my destination view controller's view was not loaded yet when trying to assign text to each UITextField.
So I added two variables of type String in my destination view controller to hold the data from my prepareForSegue function instead of trying to assign the text from the selected UITableView row directly to the UITextField and then in viewWillAppear I assigned those variables to each UITextField.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "edit" {
if let inputController = segue.destinationViewController as? QAInputViewController {
let uri = currentDeck!.objectID.URIRepresentation()
let objectID = managedContext.persistentStoreCoordinator?.managedObjectIDForURIRepresentation(uri)
inputController.currentDeck = managedContext.objectWithID(objectID!) as? Deck
if let indexPath = tableView.indexPathForCell(sender as! DisplayTableViewCell) {
let data = fetchedResultsController.objectAtIndexPath(indexPath) as? Card
inputController.selectedQuestion = data!.question
inputController.selectedAnswer = data!.answer
}
}
}
}
In my destination view controller:
var selectedQuestion: String = ""
var selectedAnswer: String = ""
override func viewWillAppear(animated: Bool) {
questionInput.text = selectedQuestion
answerInput.text = selectedAnswer
}