I know the implicitly unwrapping optional value question has been answered a million times, but this is so weird. I used storyboard?.instantiateViewController(identifier: "SettingsViewController") to create the current view controller, but I can't access the properties of the sending view controller. Im getting the error from the optional value of an isHidden property of an object in the sending view controller being nil. I checked to make sure that all the required outlets are properly linked, and they are as far as I can tell. No idea what's going on. Here's the code where isHidden is nil:
#IBAction func hideSearchRadiusPressed(_ sender: UIButton) {
if hideSearchRadiusButton.titleLabel?.text == "Hide Search Radius" {
mapViewController.searchRadiusView.isHidden = true
mapViewController.searchRadiusView.isUserInteractionEnabled = false
hideSearchRadiusButton.titleLabel?.text = "Show Search Radius"
} else if hideSearchRadiusButton.titleLabel?.text == "Show Search Radius" {
mapViewController.searchRadiusView.isHidden = false
mapViewController.searchRadiusView.isUserInteractionEnabled = true
hideSearchRadiusButton.titleLabel?.text = "Hide Search Radius"
}
}
Here is the code in which the current view controller (SettingsViewController), is instantiated. this is done within MapViewController, the initial view controller:
#IBAction func settingsButtonPressed(_ sender: UIBarButtonItem) {
// Identifier is under 'Storyboard ID' in the identity inspector for SettingsViewController
guard let settingsViewController = storyboard?.instantiateViewController(identifier: "SettingsViewController") else {return}
settingsViewController.modalPresentationStyle = .overCurrentContext
settingsViewController.transitioningDelegate = self
present(settingsViewController, animated: true)
}
I get the error on the 'mapViewController.searchRadiusView.isHidden = true' line, but I'm sure Id get it for the isUserInteractionEnabled part as well. Any idea why this error would occur on an isHidden property? Again the outlet for the searchRadiusView (which is in another view controller, that's why I call it as a part of mapViewController) is properly linked. thanks for any help.
Well, I solved my own problem. I'm going to make this more general in case anyone else runs into this issue. If you are instantiating what I will call a 'newViewController' programmatically, like I was, you will need to add a transitioning delegate:
class SendingViewController: UIViewController {
#IBAction func sendingButtonPressed(_ sender: UIBarButtonItem) {
// Identifier argument of 'instantiateViewController' is under 'Storyboard ID' in the identity inspector for NewViewController
guard let newViewController = storyboard?.instantiateViewController(identifier: "NewViewController") else {return}
// Presentation style up to you. I did it this way because I am using a custom transition
newViewController.modalPresentationStyle = .overCurrentContext
// Set the newViewController's transitioningDelegate property to self (the sending view controller)
newViewController.transitioningDelegate = self
present(newViewController, animated: true)
}
}
In NewViewController, when you want to access the properties of the SendingViewController, all you have to do is reference the transitioning delegate:
class NewViewController: UIViewController {
#IBAction func buttonPressed(_ sender: UIButton) {
// Remember, we set the current view controller's transitioningDelegate as SendingViewController before, when we were INSIDE SendingViewController, by using newViewController.transitioningDelegate = self
if let sendingVC = self.transitioningDelegate as? SendingViewController {
// Now we can access properties of the sendingVC.
// In my case, I needed to access a UIView, put your code below in place of mine
sendingVC.customView.isHidden = true
sendingVC.customView.isUserInteractionEnabled = false
dismiss(animated: true, completion: nil)
}
}
}
Hopefully this helps someone.
I'll give an example of what I want so it's not so confusing:
Example:
Let's say that I have a map that adds every time that my user scrolls 3 annotations dynamically. Now I have a button under the map and when I press it I go to another viewController do what I want and get back to the viewController with the map, now I want to find all the annotations that my map had and not reload the view at all.
I used to use this function that I made to move between viewControllers:
func move(identifier: String , viewController : UIViewController) -> Void {
let mstoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let vc: UIViewController = mstoryboard.instantiateViewControllerWithIdentifier(identifier)
viewController.presentViewController(vc, animated: true, completion: nil)
}
I also tried this:
let vc = self.storyboard?.instantiateViewControllerWithIdentifier("view") as? MyViewcontroller
self.presentViewController(vc!, animated: true, completion: nil)
These two when I use them the viewcontroller that appears is calling viewDidload so its like it appeared for the first time.
Another example is the tabBarViewController if you notice when you navigate through tabs nothing reloads (only function that is called is viewDidAppear )
EDIT
test file
The problem is caused by the fact that the map controller gets deallocated when navigating back to the other controller, and another one is created when you want to move again to the map screen.
What you need is to hold on onto the same controller instance, and present that one. Keeping a strong reference in the presenting controller would suffice.
class PresentingController {
// making the property lazy will result in the getter code
// being executed only when asked the first time
lazy var mapController = { () -> UIViewController in
let mstoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
return mstoryboard.instantiateViewControllerWithIdentifier("mapControllerIdentifier")
}()
func moveToMap() {
// simply use the mapController property
// the property reference will make sure the controller won't
// get deallocated, so every time you navigate to that screen
// you'll get the same controller
presentViewController(mapController, animated: true, completion: nil)
}
}
According to the same project you posted, you instantiate a new UIViewController when going from view 2 back to view 1 and that is why your viewDidLoad gets called again and your entire map view is reloaded.
In your sample project, instead of
lazy var mapController2 = { () -> UIViewController in
let mstoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
return mstoryboard.instantiateViewController(withIdentifier: "first")
}
You should just dismiss your view 2 on the button press.
#IBAction func butto(_ sender: AnyObject) {
//Your initial code
//PresentingController().moveToMap(self, flag: 1)
self.dismiss(animated: true, completion: nil)
}
When you present a new UIViewController, the older UIViewController is not removed from memory, it is just hidden behind the new UIViewController. So whenever you wish to go back to a UIViewController with the previous state maintained, all you need to do is close the new UIViewController
However, if you are doing some tasks that you performed on your second UIViewController that you wish to be reflected in your initial UIViewController, you will have to setup closures to update your initial UIViewController.
Suppose I have three view controllers in a Main.storyboard. Two of the three, vc_login and vc_studyDesc load the other view controller using a UIButton with 'present modally' option.
The other one vc_signup has a UIButton, which may go back to the previous controller. To implement this, I used the following methods:
vc_studyDesc has an identifier of studyDesc; I let it pass its identifier to vc_signup. In the same way, vc_login has login as an identifier.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if sender as! UIButton == qnaSignUp {
let signup = segue.destinationViewController as! vc_signup
signup.latestVC = "studyDesc"}}
This one is in the UIViewController class for vc_signup. By referencing a string latestVC, the method determines which VC to move on.
#IBAction func backBtnClick(sender: UIButton) {
print("latestVS: \(latestVC)")
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier(latestVC)
vc.modalTransitionStyle = UIModalTransitionStyle.CrossDissolve
print("check check")
self.presentViewController(vc, animated: true, completion: nil)}
The problem I have is that the app gets terminated when vc_studyDesc is called by vc_signup. I found that this is because I missed a significant variable which must be loaded in vc_signup.
vc_studyDesc has some data to be referenced from Firebase when it is loaded. I did this by loading a variable postID from the prior vc to vc_studyDesc; which is vc_list.
So I just saved postID using NSUserdefaults.standardUserDefaults(). It is solved but I'm wondering if there's any way to pass data using the way I used in vc_signup.
As far as I see, I cannot find any way to pass the data into vc_studyDesc.swift; for the vc is chosen by its identifier..
Can I pass the variable I want in the way I want?? And adding tags would be appreciated!
So there are a couple problems with this design.
When you instantiate a viewController you are creating a new instance of that class, and presenting it adds it to the stack. Think of the stack like a deck of cards, you start with one card and then add or remove them, the top card being the visible vc. When you are going back to studyDesc you are instantiating and presenting it so you will have 3 VCs in your stack, of which two are studyDesc (the one you started with and the one you add when you try to go back)
To remove a VC from the stack you can use
dismissViewController(animated: true, completion: nil)
or if you have the VCs in a navigation controller you can use
popViewControllerController(animated: true, completion: nil)
in terms of passing information between viewControllers, if the info is in the VC you use to present your new controller you can use prepareForSegue like you already have. To pass information back you should use a delegate pattern. So to implement a delegate pattern in this case you would do the following:
Declare a protocol (not inside your classes, above there but below your import's)
protocol SignUpDelegate {
signInCompleted(infoToPass: AnyObject)
}
Then have your studyDesc class conform to this protocol and implement the function signInCompleted
StudyDescVC: UIViewController, SignUpDelegate {
func signInCompleted(infoToPass: AnyObject) {
// do what you want with the info here
}
}
Then in your signUpVc add a var delegate (which will be used to call the signInCompeleted function)
class SignInVC: UIViewController {
var delegate: SignUpDelegate!
func finishedSigningIn() {
delegate.signInCompleted(infoToPass: //yourinfo)
self.dismissViewControllerAnimated(true, completion: nil)
}
And then in your prepareForSegue set the delegate
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if sender as! UIButton == qnaSignUp {
let signup = segue.destinationViewController as! vc_signup
signup.delegate = self
}
}
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier(latestVC) as! YOUR_VIEW_CONTROLLER_NAME
vc.modalTransitionStyle = UIModalTransitionStyle.CrossDissolve
vc.name = "Andrew"
print("check check")
self.presentViewController(vc, animated: true, completion: nil)
//set a variale or property to your viewController
class YOUR_VIEW_CONTROLLER_NAME: UIViewController {
var name: String?
}
This is my first application for iOS.
So I have a UIVIewController with a UITableView where I have integrated a UISearchBar and a UISearchController in order to filter TableCells to display
override func viewDidLoad() {
menuBar.delegate = self
table.dataSource = self
table.delegate = self
let nib = UINib(nibName: "ItemCellTableViewCell", bundle: nil)
table.registerNib(nib, forCellReuseIdentifier: "Cell")
let searchButton = UIBarButtonItem(barButtonSystemItem: .Search, target: self, action: "search:")
menuBar.topItem?.leftBarButtonItem = searchButton
self.resultSearchController = ({
let controller = UISearchController(searchResultsController: nil)
controller.searchResultsUpdater = self
controller.dimsBackgroundDuringPresentation = false
return controller
})()
self.table.reloadData()
}
I am using also a modal segue in order to open the element's ViewController where I will display details of the element.
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
self.index = indexPath.row
self.performSegueWithIdentifier("ItemDetailFromHome", sender: self)
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if (segue.identifier == "ItemDetailFromHome") {
let settingsVC = segue.destinationViewController as! ItemDetailViewController
settingsVC.parent = self
if self.isSearching == true && self.searchText != nil && self.searchText != "" {
settingsVC.item = self.filteredItems[self.index!]
} else {
settingsVC.item = self.items[self.index!]
}
}
}
That works fine until I try to display the ItemDetailViewController for a filtered element (through the UISearchController).
I have the following message :
Warning: Attempt to present <ItemDetailViewController: *> on <HomeViewController: *> which is already presenting (null)
At every time I am going to the ItemDetailViewController.viewDidLoad() function but after that when the search is activated I have the previous error.
Any idea ? I have tried to use the following async dispatch but without success
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
self.index = indexPath.row
dispatch_async(dispatch_get_main_queue(), { () -> Void in
self.performSegueWithIdentifier("ItemDetailFromHome", sender: self)
})
}
I have found out a solution.
I have add the following code in HomeViewController.viewDidLoad and that works !
definesPresentationContext = true
In my case, I found my code to present the new viewController (a UIAlertController) was being called twice.
Check this before messing about with definesPresentationContext.
In my case, I tried too early to show the new UIViewController before closing the previous one. The problem was solved through a call with a slight delay:
DispatchQueue.main.asyncAfter(deadline: .now() + 0.3) {
self.callMethod()
}
The problem for me is that I was presenting two modals and I have to dismiss both and then execute some code in the parent window ... and then I have this error... I solved it seting this code in the dismiss o the last modal presented:
self.dismiss(animated: true, completion: {
self.delegate?.callingDelegate()
})
in other words instead of just dismiss two times .. in the completion block of the first dismiss call delegate that will execute the second dismiss.
What worked for me was to add the presentation of the alert to the main thread.
DispatchQueue.main.async {
self.present(alert, animated: true)
}
The presentation of the current viewController was not complete. By adding the alert to the main thread it can wait for the viewController's presentation to complete before attempting to present.
I got the same issue when i tried to present a VC which called inside the SideMenu(jonkykong).
first i tried inside the SideMenu and i called it from the delegate to the MainVC both had the same issue.
Solution: dismiss the SideMenu first and present the new VC after will works perfectly!.
This happened with me on our project. I was presenting our log in/log out ViewController as a pop-over. But whenever I tried to log back out again and display the pop-over again, I was getting this logged out in my console:
Warning: Attempt to present UIViewController on <MY_HOME_VIEW_CONTROLLER> which is already presenting (null)
My guess is that the pop-over was still being held by my ViewController even though it was not visible.
However you are attempting to display the new ViewController, the following code I used to solve the issue should work for you:
func showLoginForm() {
// Dismiss the Old
if let presented = self.presentedViewController {
presented.removeFromParentViewController()
}
// Present the New
let storyboard = UIStoryboard(name: "MPTLogin", bundle: Bundle(for: MPTLogin.self))
let loginVC = storyboard.instantiateViewController(withIdentifier: "LogInViewController") as? MPTLogInViewController
let loginNav = MPTLoginNav(rootViewController: loginVC!)
loginNav.modalPresentationStyle = .pageSheet;
self.present(loginNav, animated: true, completion: nil)
}
I faced the same kind of problem
What I did is from Interface builder selected my segue
Its kind was "Present Modally"
and its presentation was "Over current context"
i changed the presentation to "Default", and then it worked for me.
In my case I was trying to present a UIAlertController at some point in the app's lifetime after using a UISearchController in the same UINavigationController.
I wasn't using the UISearchController correctly and forgot to set searchController.isActive = false before dismissing. Later on in the app I tried to present the alert but the search controller, though not visible at the time, was still controlling the presentation context.
My problem was that (in my coordinator) i had presented a VC on a VC and then when i wanted to present the next VC(third one), presented the third VC from the first one which obviously makes the problem which is already presenting.
make sure you are presenting the third one from the second VC.
secondVC.present(thirdVC, animated: true, completion: nil)
Building on Mehrdad's answer: I had to first check if the search controller is active (if the user is currently searching):
if self.searchController.isActive {
self.searchController.present(alert, animated: true, completion: nil)
} else {
self.present(alert, animated: true, completion: nil)
}
where alert is the view controller to present modally.
This is what finally worked for me, as my project didn't exactly have a NavigationVC but instead, individual detached VC's. as xib files
This code produced the bug:
present(alertVC, animated: true, completion: nil)
This code fixed the bug:
if presentedViewController == nil{
navigationController?.present(alertVC, animated: true, completion: nil)
}
For me it was an alert that was interfering with the new VC that I was about to present.
So I moved the new VC present code into the OK part of my alert, Like this :
func showSuccessfullSignupAndGoToMainView(){
let alert = UIAlertController(title: "Alert", message: "Sign up was successfull.", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { action in
switch action.style{
case .default:
// Goto Main Page to show businesses
let mainStoryboard = UIStoryboard(name: "Main", bundle: Bundle.main)
let vc : MainViewController = mainStoryboard.instantiateViewController(withIdentifier: "MainViewController") as! MainViewController
self.present(vc, animated: false, completion: nil)
case .cancel:
print("cancel")
case .destructive:
print("destructive")
}}))
self.present(alert, animated: true, completion: nil)
}
My issue was that I was trying to present an alert from a view that wasn't on top. Make sure you present from the top-most viewController.
In my case this was an issue of a button which was duplicated in Interface Builder. The original button had a touch-up handler attached, which also presented a modal view. When I then attached a touch-up handler on the copied button, I forgot to remove the copied handler from the original, causing both handlers to be fired and thus creating the warning.
More than likely you have your Search button wired directly to the other view controller with a segue and you are calling performSegueWithIdentifier. So you are opening it twice, which generates the error that tells you "is already presenting."
So don't call performSegueWithIdentifier, and that should do the trick.
Make sure you Dismiss previous one before presenting new one!
#IBAction func DoneButton(sender: AnyObject) {
self.dismissViewControllerAnimated(true, completion: nil)
let viewController = self.storyboard?.instantiateViewControllerWithIdentifier("ViewController") as UIViewController
viewController.viewWillAppear()
}
Its suppose to dismiss my current view and reload ViewController
but it crashes with fatal error: unexpectedly
found nil while unwrapping an Optional value
is it because I'm dismissing before?
The call to instantiateViewControllerWithIdentifier() returns an optional. So if the view controller with the specified identifier cannot be found in your storyboard, it will be set to nil and the next line where you call viewWillAppear will crash.
It is also possible that you crash inside viewWillAppear actually. That is not a method that you should call. Instead, UIKit will call that method for you when your view controller is presented.
I guess what you are trying to do is something like this:
if let viewController = self.storyboard?.instantiateViewControllerWithIdentifier("ViewController") as UIViewController {
self.presentViewController(viewController,
animated: true, completion: nil)
}
If not, provide more context to your question.
I was thinking to do either
1.
let viewController = ViewController()
viewController.viewWillAppear(false)
2.
In secondary class:
let viewController = ViewController()
viewController.shouldRefresh = true
In primary class:
var shouldRefresh: Bool!
override func viewWillAppear(animated: Bool) {
if shouldRefresh == true {
}
}
3.
In secondary class:
let viewController = ViewController()
viewController.reloadRoutineData()
In primary class:
func reloadRoutineData() {
// Do my stuff here
}
The third option is my variable because I only need to do certain code, not really reload the view completely. But all of them crash with nil while unwrapping.