I'm getting nil when unwrapping an optional value with GADBannerView..
I setup my ad banner like this, in FlashViewController.swift..
class FlashViewController: UIViewController {
#IBOutlet weak var bannerView: GADBannerView!
and then in ViewDidLoad:
func initAdMobBanner() {
bannerView.adUnitID = "ca-app-pub-3940256099942544/2934735716"
bannerView.rootViewController = self
bannerView.load(GADRequest())
}
bannerView has an outlet in storyboard to Root View Controller, which is class FlashViewController.
Then in TableViewController.swift I have my purchase button. Purchase button runs:
FlashViewController().HideMyBanner();
The function HideMyBanner is in FlashViewController and will run this code:
if bannerView != nil {
print("bannerview Contains a value!")
bannerView.isHidden = true
} else {
print("bannerview Doesn’t contain a value.")
}
The issue is, if I create a button directly in FlashViewContorller.swift and run the same function, bannerView contains a value and can be hidden.. If I call the function from TableViewController.swift, it returns nil, (or crashes if I try to hide bannerView... I feel like I missing something easy here, but already spent a long time trying to figure it out...
By using this line FlashViewController().HideMyBanner(); you are creating new object of FlashViewController. so it will crash.you need to use the object of FlashViewController which is already created and loaded in memory.
I think you need to pass the reference of FlashViewContorller to TableViewController
If your TableViewController is load from FlashViewContorller than you need to create reference FlashViewContorller in TableViewController like this way.
class TableViewController: UIViewController {
var objFlashViewContorller : FlashViewContorller?
override func viewDidLoad() {
super.viewDidLoad()
//This is the UILabel
}
func purchasebuttonClick() {
objFlashViewContorller?.HideMyBanner();
}
}
While setup Navigation FlashViewContorller to TableViewController you need to pass reference.
let tableViewController = self.storyboard!.instantiateViewController(withIdentifier: "TableViewController") as! TableViewController
tableViewController.objFlashViewContorller = self
self.navigationController?.pushViewController(tableViewController, animated: true)
OR
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "TableViewController" {
let vc = segue.destinationViewController as! TableViewController
vc.objFlashViewContorller = self
}
Don't use FlashViewController().HideMyBanner();
I think you need to use this in in TableViewController.swift -> my purchase button method.
self.revealViewController.frontViewController.HideMyBanner()
I used Notifications to finally work this out... Controller 2 sends a notification that a purchase has been made, and Controller 1 observes and waits for this notification, then takes care of hiding the banner in Controller 1.
https://blog.bobthedeveloper.io/pass-data-with-nsnotification-in-swift-3-73743723c84b
Related
I have a view controller, lets call it vc1, which passes some data to another (vc2) using prepare for segue, and then calling performSegue.
Is there a way to pass some data back from vc2 to vc1 when vc2 is dismissed by swiping down?
Thanks,
Edit --
Apologies for the lack of information, very new to swift so unsure of the correct question to ask in this situation.
To elaborate, the root of the issue at the moment is that vc2 is not dismissed programatically. ie there is currently no function called, it is simply dismissed by the user swiping down.
Is there some function that I can include to capture this dismissal, and use it to send data back to vc1?
I would prefer not to add any buttons to vc2 if possible.
Apologies again, and I appreciate all the help given already!
Try This
class VCOne: UIViewController {
//Create a shared instance of VCOne
static var sharedInstance:VCOne?
//Let the data to be passed back to VCOne is of type string
var dataToBePassedBack:String?
override func viewDidLoad() {
super.viewDidLoad()
//set the sharedInstance to self
VCOne.sharedInstance = self
}
}
Class VCTwo:UIViewController{
//function in which you are dismissing your current VC you can use the shared
instance to pass the data back
func dismissVC(){
//before dismissing the VCTwo you can set the value for VCOne
VCOne.sharedInstance?.dataToBePassedBack = "data"
}
}
Using Protocol And Delegate You Do or Other Option is NSotificationcenter.
One way yo do it is to create another file that it the controller of everything and then have a delegate that always notifies the view controllers when new changes are available. I will walk it through.
protocol HeadControllerDelegate {
// Create a function that sends out the data to the delegates when it is called
// You can use your custom struct here to pass more data easly
func didReciveNewData(myData: String?)
}
struct HeadController {
// Create a shared instance so that the viewcontroller that conforms to the view as well as when we sends out the data the delegate is correct
static var shared = HeadController()
// Creates the delegate, every view can asign it to
public var delegate: HeadControllerDelegate?
// Add all your values here you want to pass back
var myValue: String? {
// The didSet gets called every time this value is set, and then is it time to call the delegate method
didSet {
// Calls the delegates didReciveMethod to notify the delegates that new data exsists
delegate?.didReciveNewData(myData: myValue)
}
}
}
Now in your viewcontroller class where you would like the data to be avaiable (as you said when you swipe down)
class ViewController: UIViewController {
// Here you create a property of the shared instance
let headController = HeadController.shared
override func viewDidLoad() {
super.viewDidLoad()
// Set yourself as the delegate for the headController delegate to recive data
headController.delegate = self
}
}
extension ViewController: HeadControllerDelegate {
// here will the data be recived
func didReciveNewData(myData: String?) {
// handle the data here, you have now got newData
print(myData)
}
}
In the class where you want to pass data you just do it like this. The beauty of this is that you can have multiple classes or structs that writes to the head controllers data (just make sure you do it thought the shared instance). It is also a good pracice according to we to use the delegate pattern.
class Sender {
var headController = HeadController.shared
func sendData(data: String) {
// Here you change the data of the headcontroller wich will send the data to all the delegates
headController.myValue = data
}
}
Hope this answer helps. If you have any questions please let me know.
UPDATE -- EASIER SOLUTION
Here is an easier solution but is less scalable as the previous one according to me.
In prepareForSegue simply pass over your current viewContorller as a field in the destination view controller. Then when viewDidDissapear in the new view controller you can simply pass back the data. Not to worry, I will show you!
In prepare for Segue
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let dc = segue.destination as? SecondViewController {
dc.viewController = self
}
}
And declare the secondViewContorller as following. The ViewDidDisappear method will be called when the view has dismissed, and therefore can you pass over the data to the view controller you have set before using the prepare for segue method.
class SecondViewController: UIViewController {
var viewController: UIViewController?
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidDisappear(_ animated: Bool) {
(viewController as? ViewController)?.value = 2
}
}
Then you could update the UI using a didSet, which simply will be called when the property is set, which will be done in the view did disappear method.
var value: Int = 0 {
didSet {
print(value)
text?.text = "\(value)"
}
}
Hope this helps!
Trying to pass data from one view controller MainScreenVC to Another RatesVC with protocol and extension, but that's not working, app crashing everytime . I'm clearly see that problem with code on second VC(because print showing correct data after action on first VC) but not sure where is error.
StoryBoard and 1st VC Example
Second VC
1st View controller
import UIKit
protocol transferNameOfCurrency {
func currencySelected(nameOfCurrency: String)
}
class MainScreenVC: UIViewController {
var transferCurrencyDelegate: transferNameOfCurrency?
var nameOfTheCurrency: String?
#IBAction func updateRates(_ sender: Any) {
nameOfTheCurrency = "EUR"
transferCurrencyDelegate?.currencySelected(nameOfCurrency:
nameOfTheCurrency)
print(nameOfTheCurrency)
}
}
2nd ViewController
import UIKit
class RatesVC: UIViewController {
var currencySelected: String?
override func viewDidLoad() {
super.viewDidLoad()
if let push = self.storyboard?.instantiateViewController(withIdentifier: "MainScreenVC") as? MainScreenVC
{
push.transferCurrencyDelegate = self
}
// Do any additional setup after loading the view.
}
}
extension RatesVC: transferNameOfCurrency {
func currencySelected(nameOfCurrency: String) {
currencySelected = nameOfCurrency
print(currencySelected)
}
}
The most obvious problem lies here:
if let push = self.storyboard?.instantiateViewController(withIdentifier: "MainScreenVC") as? MainScreenVC {
push.transferCurrencyDelegate = self
}
You have to realize that instantiateViewController creates a new view controller - it's not the reference to the view controller presented at the screen. In that code you just created a completely new view controller and then set its delegate to self, but otherwise nothing else.
Without knowing the context it is really hard to suggest anything - prepare(for:) segue might be the place where you want to set the delegate. Anyway, the problem is that you have to obtain a reference to the controller that is presented on the screen, the one that is supposed to be reacting to those events.
Moreover, from the memory management aspect, you should really consider making the delegate property a weak one to prevent memory leaks.
EDIT
So after seeing the minimal working example you provided at link, I think I can provide the solution on how to get that string to the SecondVC.
Your first view controller with comments:
import UIKit
class ViewController: UIViewController {
var newLine: String = "EUR"
#IBAction func push(_ sender: Any) {
// here the secondVC does not exist yet, calling delegate.transferWord() here would have no sense
// performSegue will create that secondVC, but now it does not exist, nor it is set up as the delegate
self.performSegue(withIdentifier: "ViewController", sender: navigationController)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let secondVC = segue.destination as? SecondVC, segue.identifier == "ViewController" {
// at this moment secondVC did not load its view yet, trying to access it would cause crash
// because transferWord tries to set label.text directly, we need to make sure that label
// is already set (for experiment you can try comment out next line)
secondVC.loadViewIfNeeded()
// but here secondVC exist, so lets call transferWord on it
secondVC.transferWord(word: newLine)
}
}
}
No need for delegates here, because your ViewController is the one pushing the SecondVC to the Navigation controller - that means that you can access it directly in prepare(for:), as you can see above.
Now the SecondVC is super simple (I omitted unnecessary code):
import UIKit
class SecondVC: UIViewController {
#IBOutlet weak var label: UILabel!
func transferWord(word: String) {
label.text = word
}
}
Storyboards can stay as they are.
i have a ViewController which is already loaded from the beginning of the app Lunching i need when the user logout from his AccountViewController ,so the Logout Icon in Side menu got hidden.
So in the Homepage i made that Protocol :
protocol HomeViewControllerDelegate {
func Menucheck()
}
then assign the delegate in ViewDidload():
var delegate: HomeViewControllerDelegate?
override func viewDidLoad() {
super.viewDidLoad()
delegate?.Menucheck()
then in the Side MenuViewController i did like that:
in ViewDidLoad():
let secondVC = Storyborad.instantiateViewController(withIdentifier: "HomeViewController") as! HomeViewController
secondVC.delegate = self
then i have used the delegate function like that:
extension SideMenuViewController: HomeViewControllerDelegate {
func Menucheck() {
print("i can hear you :) ")
if(preferences.double(forKey: User_ID) == 0)
{
LogoutSideIcon.isHidden = true
}else {
LogoutSideIcon.isHidden = false
}
}
Now when i go to homeViewController i suppose to see ("i can hear you") at least ,but actually nothing happen,i have tried to add to (Viewdidload) instead ,and i have tried to add it to a button action but nothing is happen ...
I’m trying to pass data between two ViewControllers with the initial call being made from a UITabBarController.
Here is what I’m doing. I’m using a class called RaisedTabBarController to add a custom button to a TabBarController, which works fine displaying the button, my issue is that when I tap the custom button I want it to take me to FirstViewController and then I want to pass data from FirstViewController to SecondViewController via protocols but for some reason I’m getting an error that in my opinion doesn’t make any sense, it complains about a labels not being accessible within SecondViewController.
Here is the error:
fatal error: unexpectedly found nil while unwrapping an Optional value
Here is the code…
Class ref from GitHub:
RaisedTabBarController
TabBarController
Here I'm adding the custom button and making the call to go to FirstViewController
import UIKit
/// TabBarController subclasses RaisedTabBarController
class TabBarController: RaisedTabBarController {
override func viewDidLoad() {
super.viewDidLoad()
// Insert empty tab item at center index. In this case we have 5 tabs.
self.insertEmptyTabItem("", atIndex: 2)
// Raise the center button with image
let img = UIImage(named: “myImage”)
self.addRaisedButton(img, highlightImage: nil, offset: -10.0)
}
// Handler for raised button
override func onRaisedButton(_ sender: UIButton!) {
super.onRaisedButton(sender)
// Go to FirstViewController
let pvc = storyboard?.instantiateViewController(withIdentifier: “firstStoryBoardID”) as! FirstViewController
/// Here, I’m not sure if this is the right way to tell that
/// SecondViewController will be the delegate not TabBarController, seem to work
pvc.delegate = SecondViewController() as FirstViewControllerDelegate
self.present(pvc, animated:true, completion:nil)
}
}
FirstViewController
From here I want to send data to SecondViewController
protocol FirstViewControllerDelegate {
func messageData(greeting: String)
}
class FirstViewController: UIViewController{
override func viewDidLoad() {
super.viewDidLoad()
}
func sendData() {
self.delegate?.messageData(greeting: “Hello SecondViewController”)
}
}
SecondViewController
Here I want to receive the data sent from FirstViewController
class SecondViewController: UIViewController, FirstViewControllerDelegate{
#IBOutlet weak var labelMessage: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
func messageData(greeting: String) {
/// I do get message from FirstViewController
print(" Message received from FirstViewController: \(greeting)")
/// Here I get error, fatal error: unexpectedly found nil while unwrapping an Optional value
/// I think it has something to do with the labelMessage not being accessible, but why?
labelMessage.text = greeting
}
}
Any idea why am I getting the error in SecondViewController, why wouldn't labels be accessible if they are declared in SecondViewController?
Ideally I would like to be able to call method onRaisedButton(_ sender: UIButton!) directly from SecondViewController but without having to subclass RaisedTabBarController. I’m not usr if this would solve the error but I think this would make my code cleaner.
EDIT: 06/19/2017 - Solved
The effect I was looking for can be done directly in XCode, in the storyboards. I stopped using the third party class (RaisedTabBarController), problem solved.
This seems wrong.
pvc.delegate = SecondViewController() as FirstViewControllerDelegate
Try to instantiate the SecondViewController like you did for the first from storyboard.
let svc = storyboard?.instantiateViewController(withIdentifier: “secondStoryBoardID”) as! SecondViewController
And then set the delegate to SecondViewController
pvc.delegate = svc
I am re-writing a tutorial converting the code from Objective-C to swift. The app moves from VC one where there is 3 sliders (Red, Green and Blue) that set the background colour, a label of the colour name and a button that links to the second VC. In the second VC the colour from the first VC is used as the background and the user has a chance to name the colour.
When the user enters the colour name it should return the new colour name to the orginal VC and the label that shows the colour name should show the text entered.
The following is the code that is causing issue:
func textFieldShouldReturn(nameEntry: UITextField) -> Bool
{
ViewController().colourLabel.text = nameEntry.text
nameEntry.resignFirstResponder()
dismissViewControllerAnimated(true, completion: nil)
return true
}
The error "fatal error: unexpectedly found nil while unwrapping an Optional value" is generated. However debugging nameEntry.text has a string in it.
I'm a little stumped. I could try and do a prepare for unwind segue but it is meant to be a tutorial app.
Cheers
ViewController() actually creates a new instance of your ViewController. This is not a reference to the already existing ViewController. What you can do is create a weak variable pointing to first ViewController inside the second ViewController and set it at prepareForSegue or when the second View controller is shown.
class SecondViewController : UIViewController {
weak var firstViewController : ViewController?
// Other code
func textFieldShouldReturn(nameEntry: UITextField) -> Bool
{
firstViewController?.colourLabel.text = nameEntry.text
nameEntry.resignFirstResponder()
dismissViewControllerAnimated(true, completion: nil)
return true
}
}
Inside First View Controller prepareForSegue
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "SecondViewController" {
let secondViewController = segue.destinationViewController as SecondViewController
secondViewController.firstViewController = self
}
}
It's possible that the view controller returned by ViewController() has not yet loaded its views. You could try checking this in a setter function and storing it for later use once the views have been loaded.
class VC : UIViewController {
#IBOutlet weak var colourLabel: UILabel!
var savedLabelText: String?
override func viewDidLoad() {
super.viewDidLoad()
self.colourLabel.text = self.savedLabelText
}
func setColorLabelText(label: String) {
if self.isViewLoaded() {
self.colourLabel.text = label
}
else {
self.savedLabelText = label
}
}
}