My Desire Output:
i want to pass data with direct initializing of a second viewController
in my first vc :
class MainViewController : UIViewController {
#IBAction func nextQuestion(_ sender: UIButton ) {
//enter code here
questionIndex += 1
let currentQuestion = exam1[questionIndex]
questionLabel.text = currentQuestion.question
//enter code here
let svc = SecondViewController()
svc.label.text = "some data from mainvc"
}
in my secondvc :
class SecondViewController : UIViewController {
#IBOutlet weak var label : UILabel!
}
// any error is not showed up when I write code an the simulator works. but when it comes to sending data to svc app crashes and gives error " found nil while unwrapping optional"
The problem is that when you do:
let svc = SecondViewController()
You are initializing without the information you put in the Storyboard (assuming you are using storyboards). Hence, so the UILabel is never initialized.
Solution
In order to solve that replace the line:
let svc = SecondViewController()
for
let svc = UIStoryboard(name: "YourStoryboardName", bundle: nil).instantiateViewController(withIdentifier: "YourViewIdentifier") as! SecondViewController
Related
Variable cards in second ViewController should be updated in first VC on buttonClick.
I tested the sending data from the first VC with printing data and it works good.
Here is the code:
#IBAction func btnTapped(_ sender: Any) {
let mainStoryboard = UIStoryboard(name: "Main", bundle: Bundle.main)
let secondVC = (mainStoryboard.instantiateViewController(withIdentifier: "SecondViewController") as! SecondViewController)
for card in setsOfCardsByLevel {
cardVC.cards.append(card)
}
print("Number of cards to send - \(cardVC.secondVC.count)") //PRINTS RIGHT NUMBER
presentVC("SecondViewController") //WORKS FINE
}
Maybe you dont need this method below but I will put it just in case:
func presentVC(_ VC_Name: String) {
guard let myVC = self.storyboard?.instantiateViewController(withIdentifier: VC_Name) else { return }
let navController = UINavigationController(rootViewController: myVC)
navController.modalPresentationStyle = .fullScreen
self.navigationController?.present(navController, animated: true, completion: nil)
}
PROBLEM: When I print cards in the secondViewController, they are empty(count = 0). How?
EDIT: While waiting for answer on StackOverflow I changed presentViewController to pushViewController and print in secondVC shows right number. I am confused.
Your problem is in your presentVC method. First in your btnTapped method you instantiate your second viewController and assing your cards, again in your presentVC method instantiate another controller and it's not relevant to the first you define in your btnTapped and cards variable not assigned. For solution you can pass your secondVC as a parameter to your presentVC, not the name of storyboard
I have an array UIButtons that have a unique tag value. When a given button is pressed, I want to load and present a UIViewController that is also stored in an array of equal length.
The UIViewControllers to be presented are subclasses of a subclass of UIViewController:
class AViewController: UIViewController {}
class BViewController: AViewController {}
class CViewController: AViewController {}
class DViewController: AViewController {}
// ... etc.
I've tried storing the array of AViewController subclasses using the following:
private var array: [AViewController] = [BViewController.self, CViewController.self, DViewController.self]
but I get the error Cannot convert value of type '[BViewController].Type' to specified type '[AViewController]' for the first element.
I will then present BViewController (for instance) using the following:
let ViewController = array[button.tag].self
var viewController: AViewController
viewController = ViewController.init()
viewController.transitioningDelegate = self
viewController.modalPresentationStyle = .custom
present(viewController, animated: true)
Please let me know if this is the incorrect thought process for doing something like this please and thanks for any help.
You need instances
private var array: [AViewController] = [BViewController(), CViewController(), DViewController()]
if the vcs are in IB , then you would do
let b = self.storyboard!.instantiateViewController(withIdentifier: "bID") as! BViewController
let c = self.storyboard!.instantiateViewController(withIdentifier: "cID") as! CViewController
let d = self.storyboard!.instantiateViewController(withIdentifier: "dID") as! DViewController
Then
array = [b,c,d]
lazy var VCArray :[UIViewController] = {
return [VCinst(name: "firstVC"),VCinst(name: "secondVC"), VCinst(name: "thirdVC")]
}()
func VCinst(name:String) -> UIViewController {
return UIStoryboard(name: "Main", bundle: nil).instantiateViewController(identifier: name)
}
Alternate answer if you want to store array of view controllers as a constant.
struct AppConstant {
static let yourViewControllers: [AnyClass] = [AViewController.self,
BViewController.self, CViewController.self]
}
I would like to reuse code, so I created redirectToTabBarControllerChild
func redirectToTabBarControllerChild(storyboardName: String, tabBarIndex: Int, segueID: String, viewController: UITableViewController) {
let storyboardMain = UIStoryboard(name: storyboardName, bundle: nil)
let tabBarController = storyboardMain.instantiateViewController(withIdentifier: "TabBarController") as! UITabBarController
window?.rootViewController = tabBarController
tabBarController.selectedIndex = tabBarIndex
let navigationViewContrller = tabBarController.childViewControllers[tabBarIndex] as! UINavigationController
let currentViewContrller = navigationViewContrller.childViewControllers.first as! viewController
currentViewContrller.performSegue(withIdentifier: segueID, sender: nil)
window?.makeKeyAndVisible()
}
The last parameter I would like to pass ProfileViewController for example. But I have an error in this line: let currentViewContrller = navigationViewContrller.childViewControllers.first as! viewController
Use of undeclared type viewController
Does anyone know how I could do it?
The navigationController?.childViewControllers is an array of UIViewControllers. You´re getting the first property which means you need to cast it to as! UIViewController which will force cast it and it will not be an optional anymore.
What you want to do is to cast it to a UITableViewController, so do it like this:
if let vc = navigationViewContrller.childViewControllers.first as? UITableViewController {
// Will succeed if the first is of type UITableViewController
// Use vc in here
}
Replace viewController to UITableViewController
I have a rails api set up and one test user. I can login/logout view the api.
I have a tab app set up, and I have a LoginViewController set up to authenticate into that. My view controller (basically) looks like the below code. This doesnt work. However, the second block of code does work
I am guessing I am calling something wrong.. The first block executes and then crashes with a *** Assertion failure in -[UIKeyboardTaskQueuewaitUntilAllTasksAreFinished].. I've been spinning my wheels for hours.. tried looking into segues.. etc. Anything would help!!!
//DOES NOT WORK //
class LoginViewController: UIViewController {
#IBOutlet weak var email: UITextField!
#IBOutlet weak var password: UITextField!
#IBAction func Login(sender: AnyObject) {
func switchToTabs() {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let tabBarController = storyboard.instantiateViewControllerWithIdentifier("TabBarController") as! UITabBarController
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
appDelegate.window?.rootViewController = tabBarController
}
let authCall = PostData()
var authToken = ""
authCall.email = email.text!
authCall.password = password.text!
authCall.forData { jsonString in
authToken = jsonString
if(authToken != "") {
switchToTabs()
}
}
}
// SAME CLASS THAT DOES WORK//
class LoginViewController: UIViewController {
#IBOutlet weak var email: UITextField!
#IBOutlet weak var password: UITextField!
#IBAction func Login(sender: AnyObject) {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let tabBarController = storyboard.instantiateViewControllerWithIdentifier("TabBarController") as! UITabBarController
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
appDelegate.window?.rootViewController = tabBarController
}
My question is, why can I seemingly navigate to a new view when I don't use my api, but when I do receive my auth token.. I can't log in.
Please excuse the ugly code.. this is my first day with swift
Everytime you every do anything that changed something about the UI inside of a closure or anything that could even possibly be off the main queue, enclose it in this statement.
dispatch_async(dispatch_get_main_queue()) {
//the code that handles UI
}
This includes all code that segues inside a closure like the one you have
authCall.forData { jsonString in
authToken = jsonString
if(authToken != "") {
switchToTabs()
}
}
If you write it like so it would work
authCall.forData {
jsonString in
authToken = jsonString
if(authToken != "") {
dispatch_async(dispatch_get_main_queue()) {
switchToTabs()
}
}
}
then call your segue in switchToTabs()
If you arn't sure what queue you are on, it won't hurt to do it. As you become more familiar with scenarios that take you off the main queue, you will realize when to use it. Anytime you are in a closure and dealing with UI its a safe bet that you could leave. Obviously anything asynchronous would cause it as well. Just place your performSegueWithIdentifier inside of it and it should work.
If you make a segue on the storyboard from the view controller attatched to LoginViewController, then you click the segue you can give it an identifier. Then you just call performSegueWithIdentifier("identifierName", sender: nil) and none of the other code in switchToTabs() is necessary.
If you want to continue down the route you are taking to summon the View Controller, then I think what you are missing is these lines.
Use this below your class outside of it.
private extension UIStoryboard {
class func mainStoryboard() -> UIStoryboard { return UIStoryboard(name: "Main", bundle: NSBundle.mainBundle()) }
class func tabBarController() -> UITabBarController? {
return mainStoryboard().instantiateViewControllerWithIdentifier("TabBarController") as? UITabBarController
}
}
Then change your switchToTabs() function out for this
func switchToTabs() {
let tabBarController = UIStoryboard.tabBarController()
view.addSubview(tabBarController!.view)
//line below can be altered for different frames
//tabBarController!.frame = self.frame
addChildViewController(tabBarController!)
tabBarController!.didMoveToParentViewController(self)
//line below is another thing worth looking into but doesn't really correlate with this
//self.navigationController!.pushViewController(tabBarController!, animated: true)
}
I added in a couple comments for you to look into if you like. I believe this will do the job, but keep in mind that the direction you are headed doesn't remove the previous screen from memory. It is technically still sitting behind your new screen. I wouldn't ever recommend this for what you are trying to do, but it might not hurt if you are building something simplistic.
I've two storyboards and need to pass messages and objects. I know how to do it in the same storyboard and with .xib files, but not with two different storyboards.
My code is:
var storyboard = UIStoryboard(name: "RecibosStoryboard", bundle: nil)
var controller = storyboard.instantiateViewControllerWithIdentifier("RecibosStoryboard") as! UINavigationController
self.presentViewController(controller, animated: true, completion: nil).
// If i do: var controller = storyboard.instantiateViewControllerWithIdentifier("RecibosStoryboard") as! = TableRecibosViewController -> fails ->cannot convert TablaRecibosViewController to UINavigationController
// If i do:
/* var controller = storyboard.instantiateViewControllerWithIdentifier("RecibosStoryboard") as! UINavigationController
let vartest: TablaRecibosTableViewController = TablaTablaRecibosTableViewController()
prueba.inicioPrueba(str, strPrueba2: str2) -> two objects are nill
self.presentViewController(controller, animated: true, completion: nil).
Two objects are nill*/
My second storyboard is "RecibosStoryboard" and only has 1 view who class is TablaRecibosViewController and has a contructor method:
class TablaRecibosTableViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
#IBOutlet var tablaRecibos: UITableView!
var pruebaMansajes: String?
var pruebaMansajes2: String?
var arrayOfObjectsCellRecibos: [ObjectTableRecibos] = [ObjectTableRecibos] ()
override func viewDidLoad() {
super.viewDidLoad()
tablaRecibos.dataSource = self
tablaRecibos.delegate = self
println("Pruebas satisfactorias1 \(pruebaMansajes) \(pruebaMansajes2)")
}
func inicioPrueba(strprueba1:String, strPrueba2:String){
pruebaMansajes = strprueba1
pruebaMansajes2 = strPrueba2
}
When i execute the App or crash or print two objects = nil
I don't find the way to do. Thanks a lot.
The problem is the following "cannot convert TablaRecibosViewController to UINavigationController". Your TablaRecibosViewController is embedded inside a UINavigationController. Try the following:
if let recibosViewController = (storyboard.instantiateViewControllerWithIdentifier("RecibosStoryboard") as? UINavigationController).viewControllers.first as? TablaRecibosTableViewController {
recibosViewController.pruebaMensajes = "Hola mundo"
}
You were creating a new instance of TablaTablaRecibosTableViewController() which was not associated to the Storyboard, therefore the table view was nil and it crashed.