I'm trying to pass some data to my view controller class like this:
MyViewController *vc = [[MyViewController alloc] init];
vc.myProperty = dataToBePassed;
[self.navigationController pushViewController:vc animated:YES];
I need to make some view configuring in viewDidLoad, but it seems that viewDidload called earlier than property assignment.
Then in MyViewController implementation:
- (void)viewDidLoad
{
[super viewDidLoad];
NSLog(#"%#", self.myProperty); // Here i get myProperty = nil
}
- (void)viewWillAppear
{
[super viewWillAppear];
NSLog(#"%#", self.myProperty); // Here i get myProperty = dataToBePassed but it's to late
}
How can i get passed data in viewDidLoad method without implementing singleton or delegate patterns?
Try doing this
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:
#"MainStoryboard" bundle:[NSBundle mainBundle]];
MyViewController *vc = [storyboard instantiateViewControllerWithIdentifier:#"storyboardIdentifier"];
vc.myProperty = dataToBePassed;
[self.navigationController pushViewController:vc animated:YES];
You have to set a storyboard identifier first in the storyboard for the view controller.
While the code sample you provide looks technically correct, I'm with #john-elemans in that you need to show more code.
There is something that is referencing the view which causes it to load and therefore causes viewDidLoad to fire prematurely.
In any case, if something (such as your property) is absolutely essential to the correct building of your view structure, I'd put in its own designated initializer, e.g.,
- (id)initWithPhotoDiameter:(CGFloat)diameter
{
self = [super init...]; // some VC initializer that you should call
if (self) {
_photoDiameter = diameter;
}
return self;
}
Notice the use of the backing instance variable _photoDiameter instead of self.photoDiameter. This is about the only place in a class where you should use the backing ivar, since self is still in the process of being initialized.
Technically there are two approaches that are quite common for lifecycle handling of view controllers related to an application.
Using XIBs
When using XIBs one of the most common if not the most common process to create and setup your view controllers is done programmatically. Following this process, when you initialise the view controller you have the option of either overriding your init method in order for your view controller to have the information prior to loading the view and easing up the process of adjusting drawn content. You can also create a method within your view controller to be called in which you pass the data to be used by the view controller.
Using Storyboard
If you are using storyboards I recommend that you trust segues setup through it. I have found that they make life easier and it will allow you to use certain methods to handle the transition. One of those is prepareForSegue:sender: Within that method I have found that it is easier to setup a view controller after it's initialized accessing the destination controller. You also might consider having all data there before viewDidLoad hence following the segue approach.
I am using this code for the navigation view controller in the start
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
splashViewController *rootVC = [[splashViewController alloc]initWithNibName:#"splashViewController" bundle:nil];
self.navigator = [[UINavigationController alloc] initWithRootViewController:rootVC];
self.window.rootViewController = self.navigator;
[self.window makeKeyAndVisible];
after that i am using this simple method to push to next view
ScoreboardListViewController *SLvc = [[ScoreboardListViewController alloc]initWithNibName:#"ScoreboardListViewController" bundle:nil];
[self.navigationController pushViewController:SLvc animated:YES];
and using this to pop out from the view
[self.navigationController popViewControllerAnimated:YES];
but when i poppet and again push to the same view with different property values then viewdidload method did not run
it only runs if i just to any other view and then push to this view
i was not able to understand this abnormal behaviour. as when ever i push to any view then this viewdidload should be executed.....
for example i am doing this to get to the view
->
SLvc.trigger = #"sold";
SLvc.lblHeader.text = value;
[self.navigationController pushViewController:SLvc animated:YES];
-> then i popped out by back button by using this
[self.navigationController popViewControllerAnimated:YES];
-> then i push to the same view with different property
SLvc.trigger = #"earning";
SLvc.lblHeader.text = value;
[self.navigationController pushViewController:SLvc animated:YES]
and this time viewdidload didn't run.
This is because you are holding a strong pointer to SLvc controller. When you pop it, the view controller is retained. Initializing a new controller every time you push will solve your problem.
// below method called when pop out from the view
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
}
You can try these in your viewcontroller:
-(void) viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
// your code here
}
or
-(void)awakeFromNib
{
[super awakeFromNib];
// your code here
}
viewDidLoad() -Called after init(coder:) when the view is loaded into memory.
Similar to viewWillAppear, this method is called just before the view disappears from the screen. And like viewWillAppear, this method can be called multiple times during the life of the view controller object. It’s called when the user navigates away from the screen – perhaps dismissing the screen, selecting another tab, tapping a button that shows a modal view, or navigating further down the navigation hierarchy
viewDidLoad is called exactly once, when the ViewController is first loaded into the memory. This is where you want to instantiate any instance variables and build any views that live for the entire lifecycle of this ViewController. However, the view is usually not yet visible at this point.
However, viewWillAppear gets called every time the view appears.
I am using something like:
VC = [[SettingsViewController alloc] initWithNibName:nil bundle:nil];
viewDidLoad is not called yet.
But when I do:
VC.view.frame = CGRectMake(...);
At this point viewDidLoad is called.
But the issue is, that the view dimensions that I am passing in the above code statement is not used in the viewDidLoad method.
I think it sees that view is being used, so it is time to load the view, and after loading the view it must be assigning the frame dimensions to the view. But what if I want that view dimensions set before viewDidLoad gets called, so that I can use those dimensions in the viewDidLoad method..
Something like initWithFrame..
Also, I don't have the view dimensions in the view controller. I have to assign the view dimensions from outside of the VC.
So probably after calling initWithNibName:bundle: method I can save the view frame dimensions in some variable.. but that doesn't look like a clean solution, does it?
viewDidLoad is called when the view did load. (surprise)
so by the time you call VC.view, before it return, the viewDidLoaded will be executed and then the view is returned, and set the frame.
so from your current approach, it is not possible
anyway, why you need view frame in viewDidLoad? maybe you can move that part into viewWillAppear / viewDidAppear which is only get called when the view is about to present
You can do something like this:
In the interface
#interface SettingsViewController : ... {
CGRect _initialFrame;
}
...
- (id)initWithFrame:(CGRect)frame;
#end
In the implementation
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithNibName:nil bundle:nil];
if (self) {
_initialFrame = frame;
}
return self;
}
- (void)viewDidLoad
{
self.view.frame = _initialFrame;
[super viewDidLoad];
}
and then from the class you use these controller:
VC = [[SettingsViewController alloc] initWithFrame:CGRectMake(...)];
I have a View controller displaying some information (not table views).
I have an update call to a remote server which fills my data base. I would like to completely reload my ViewController after the update call is done.
What should I do?
If you know your database has been updated and you want to just refresh your ViewController (which was my case). I didn't find another solution but what I did was when my database updated, I called:
[self viewDidLoad];
again, and it worked. Remember if you override other viewWillAppear or loadView then call them too in same order.
like.
[self viewDidLoad];
[self viewWillAppear:YES];
I think there should be a more specific solution like refresh button in browser.
If you want to reload a ViewController initially loaded from a XIB, you can use the next UIViewController extension:
extension UIViewController {
func reloadViewFromNib() {
let parent = view.superview
view.removeFromSuperview()
view = nil
parent?.addSubview(view) // This line causes the view to be reloaded
}
}
You really don't need to do:
[self.view setNeedsDisplay];
Honestly, I think it's "let's hope for the best" type of solution, in this case. There are several approaches to update your UIViews:
KVO
Notifications
Delegation
Each one has is pros and cons. Depending of what you are updating and what kind of "connection" you have between your business layer (the server connectivity) and the UIViewController, I can recommend one that would suit your needs.
Try this, You have to call both methods to reload view,
as this one works for me,
-Objective-C
[self viewDidLoad];
[self viewWillAppear:YES];
-Swift
self.viewDidLoad()
self.viewWillAppear(true)
Update the data ... change button titles..whatever stuff you have to update..
then just call
[self.view setNeedsDisplay];
Direct to your ViewController again. in my situation [self.view setNeedsDisplay]; and [self viewDidLoad]; [self viewWillAppear:YES];does not work, but the method below worked.
In objective C
UIStoryboard *MyStoryboard = [UIStoryboard storyboardWithName:#"Main" bundle:nil ];
UIViewController *vc = [MyStoryboard instantiateViewControllerWithIdentifier:#"ViewControllerStoryBoardID"];
[self presentViewController:vc animated:YES completion:nil];
Swift:
let secondViewController = self.storyboard!.instantiateViewControllerWithIdentifier("ViewControllerStoryBoardID")
self.presentViewController(secondViewController, animated: true, completion: nil)
It is not advised to call ViewDidLoad or ViewWillAppear by yourself.
In the ViewDidLoad include a loadData() function to prepare the data. This is executed in the initial run.
When you want to reload, call loadData() again to get the data from model. In a tableView call reloadData() or in a regular view setNeedsDisplay().
Reinitialise the view controller
YourViewController *vc = [[YourViewController alloc] initWithNibName:#"YourViewControllerIpad" bundle:nil];
[self.navigationController vc animated:NO];
For UIViewController just load your view again -
func rightButtonAction() {
if isEditProfile {
print("Submit Clicked, Call Update profile API")
isEditProfile = false
self.viewWillAppear(true)
} else {
print("Edit Clicked, Call Edit profile API")
isEditProfile = true
self.viewWillAppear(true)
}
}
I am loading my view controller on profile edit and view profile. According to the Bool value isEditProfile updating the view in viewWillAppear method.
You Must use
-(void)viewWillAppear:(BOOL)animated
and set your entries like you want...
I read SO about another user encountering similar error, but this error is in different case.
I received this message when I added a View Controller initially:
Unbalanced calls to begin/end appearance transitions for
<UITabBarController: 0x197870>
The structure of the app is as follow:
I got a 5-tab TabBarController linked to 5 View Controllers. In the initial showing tab, I call out a new View Controller to overlay as an introduction of the app.
I use this code to call the introduction view controller:
IntroVC *vc = [[IntroVC alloc] init];
[self presentModalViewController:vc animated:YES];
[vc release];
After this IntroVC view controller shows up, the above error shows.
p.s. I am using xCode 4.2 & iOS 5.0 SDK, developing iOS 4.3 app.
Without seeing more of the surrounding code I can't give a definite answer, but I have two theories.
You're not using UIViewController's designated initializer initWithNibName:bundle:. Try using it instead of just init.
Also, self may be one of the tab bar controller's view controllers. Always present view controllers from the topmost view controller, which means in this case ask the tab bar controller to present the overlay view controller on behalf of the view controller. You can still keep any callback delegates to the real view controller, but you must have the tab bar controller present and dismiss.
I fixed this error by changing animated from YES to NO.
From:
[tabBarController presentModalViewController:viewController animated:YES];
To:
[tabBarController presentModalViewController:viewController animated:NO];
As posted by danh
You can generate this warning by presenting the modal vc before the app is done initializing. i.e. Start a tabbed application template app and present a modal vc on top of self.tabBarController as the last line in application:didFinishLaunching. Warning appears. Solution: let the stack unwind first, present the modal vc in another method, invoked with a performSelector withDelay:0.0
Try to move the method into the viewWillAppear and guard it so it does get executed just once (would recommend setting up a property)
Another solution for many cases is to make sure that the transition between UIViewControllers happens after the not-suitable (like during initialization) procedure finishes, by doing:
__weak MyViewController *weakSelf = self;
dispatch_async(dispatch_get_main_queue(), ^{
[weakSelf presentViewController:vc animated:YES];
});
This is general for also pushViewController:animated:, etc.
I had the same problem. I called a method inside viewDidLoad inside my first UIViewController
- (void)viewDidLoad{
[super viewDidLoad];
[self performSelector:#selector(loadingView)
withObject:nil afterDelay:0.5];
}
- (void)loadingView{
[self performSegueWithIdentifier:#"loadedData" sender:self];
}
Inside the second UIViewController I did the same also with 0.5 seconds delay. After changing the delay to a higher value, it worked fine. It's like the segue can't be performed too fast after another segue.
I had the same problem when I need to Present My Login View Controller from another View Controller If the the User is't authorized, I did it in ViewDidLoad Method of my Another View Controller ( if not authorized -> presentModalViewController ). When I start to make it in ViewDidAppear method, I solved this problem. I Think that ViewDidLoad only initialize properties and after that the actual showing view algorithm begins! Thats why you must use viewDidAppear method to make modal transitions!
If you're using transitioningDelegate (not the case in this question's example), also set modalPresentationStyle to .Custom.
Swift
let vc = storyboard.instantiateViewControllerWithIdentifier("...")
vc.transitioningDelegate = self
vc.modalPresentationStyle = .Custom
I had this problem because of a typo:
override func viewDidAppear(animated: Bool) {
super.viewWillAppear(animated)
instead of
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
It was calling "WillAppear" in the super instead of "DidAppear"
I had lot of problem with the same issue. I solved this one by
Initiating the ViewController using the storyboad instantiateViewControllerWithIdentifier method. i.e Intro *vc = [self.storyboard instantiateViewControllerWithIdentifier:#"introVC"];
[self.tabBarController presentModalViewController : vc animated:YES];
I have the viewcontroller in my storyboard, for some reason using only [[introvc alloc] init]; did not work for me.
I solved it by writing
[self.navigationController presentViewController:viewController
animated:TRUE
completion:NULL];
I had this problem with a third party code. Someone forgot to set the super inside of viewWillAppear and viewWillDisappear in a custom TabBarController class.
- (void) viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
// code...
}
or
- (void) viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
// code...
}
I had the same error. I have a tab bar with 3 items and I was unconsciously trying to call the root view controller of item 1 in the item 2 of my tab bar using performSegueWithIdentifier.
What happens is that it calls the view controller and goes back to the root view controller of item 2 after a few seconds and logs that error.
Apparently, you cannot call the root view controller of an item to another item.
So instead of performSegueWithIdentifier
I used [self.parentViewController.tabBarController setSelectedIndex:0];
Hope this helps someone.
I had the same problem and thought I would post in case someone else runs into something similar.
In my case, I had attached a long press gesture recognizer to my UITableViewController.
UILongPressGestureRecognizer *longPressGesture = [[[UILongPressGestureRecognizer alloc]
initWithTarget:self
action:#selector(onLongPress:)]
autorelease];
[longPressGesture setMinimumPressDuration:1];
[self.tableView addGestureRecognizer:longPressGesture];
In my onLongPress selector, I launched my next view controller.
- (IBAction)onLongPress:(id)sender {
SomeViewController* page = [[SomeViewController alloc] initWithNibName:#"SomeViewController" bundle:nil];
[self.navigationController pushViewController:page animated:YES];
[page release];
}
In my case, I received the error message because the long press recognizer fired more than one time and as a result, my "SomeViewController" was pushed onto the stack multiple times.
The solution was to add a boolean to indicate when the SomeViewController had been pushed onto the stack. When my UITableViewController's viewWillAppear method was called, I set the boolean back to NO.
I found that, if you are using a storyboard, you will want to put the code that is presenting the new view controller in viewDidAppear. It will also get rid of the "Presenting view controllers on detached view controllers is discouraged" warning.
In Swift 2+ for me works:
I have UITabBarViewController in storyboard and I had selectedIndex property like this:
But I delete it, and add in my viewDidLoad method of my initial class, like this:
override func viewDidLoad() {
super.viewDidLoad()
self.tabBarController?.selectedIndex = 2
}
I hope I can help someone.
This error will be displayed when trying to present an UINavigationController that is lazily initialized via a closure.
Actually you need to wait till the push animation ends. So you can delegate UINavigationController and prevent pushing till the animation ends.
- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated{
waitNavigation = NO;
}
-(void)showGScreen:(id)gvc{
if (!waitNavigation) {
waitNavigation = YES;
[_nav popToRootViewControllerAnimated:NO];
[_nav pushViewController:gvc animated:YES];
}
}
As #danh suggested, my issue was that I was presenting the modal vc before the UITabBarController was ready. However, I felt uncomfortable relying on a fixed delay before presenting the view controller (from my testing, I needed to use a 0.05-0.1s delay in performSelector:withDelay:). My solution is to add a block that gets called on UITabBarController's viewDidAppear: method:
PRTabBarController.h:
#interface PRTabBarController : UITabBarController
#property (nonatomic, copy) void (^viewDidAppearBlock)(BOOL animated);
#end
PRTabBarController.m:
#import "PRTabBarController.h"
#implementation PRTabBarController
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
if (self.viewDidAppearBlock) {
self.viewDidAppearBlock(animated);
}
}
#end
Now in application:didFinishLaunchingWithOptions:
PRTabBarController *tabBarController = [[PRTabBarController alloc] init];
// UIWindow initialization, etc.
__weak typeof(tabBarController) weakTabBarController = tabBarController;
tabBarController.viewDidAppearBlock = ^(BOOL animated) {
MyViewController *viewController = [MyViewController new];
viewController.modalPresentationStyle = UIModalPresentationOverFullScreen;
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:viewController];
[weakTabBarController.tabBarController presentViewController:navigationController animated:NO completion:nil];
weakTabBarController.viewDidAppearBlock = nil;
};
you need make sure -(void)beginAppearanceTransition:(BOOL)isAppearing animated:(BOOL)animated and -(void)endAppearanceTransition is create together in the class.
I had the same issue. When developing I wanted to bypass screens. I was navigating from one view controller to another in viewDidLoad by calling a selector method.
The issue is that we should let the ViewController finish transitioning before transitioning to another ViewController.
This solved my problem: The delay is necessary to allow ViewControllers finish transitioning before transitioning to another.
self.perform(#selector(YOUR SELECTOR METHOD), with: self, afterDelay: 0.5)
For me this error occurred because i didn't have UIWindow declared in the upper level of my class when setting a root view controller
rootViewController?.showTimeoutAlert = showTimeOut
let navigationController = SwipeNavigationController(rootViewController: rootViewController!)
self.window = UIWindow(frame: UIScreen.main.bounds)
self.window?.rootViewController = navigationController
self.window?.makeKeyAndVisible()
Ex if I tried declaring window in that block of code instead of referencing self then I would receive the error
I had this problem when I had navigated from root TVC to TVC A then to TVC B. After tapping the "load" button in TVC B I wanted to jump straight back to the root TVC (no need to revisit TVC A so why do it). I had:
//Pop child from the nav controller
[self.navigationController popViewControllerAnimated:YES];
//Pop self to return to root
[self.navigationController popViewControllerAnimated:YES];
...which gave the error "Unbalanced calls to begin/end etc". The following fixed the error, but no animation:
//Pop child from the nav controller
[self.navigationController popViewControllerAnimated:NO];
//Then pop self to return to root
[self.navigationController popViewControllerAnimated:NO];
This was my final solution, no error and still animated:
//Pop child from the nav controller
[self.navigationController popViewControllerAnimated:NO];
//Then pop self to return to root, only works if first pop above is *not* animated
[self.navigationController popViewControllerAnimated:YES];
I encountered this error when I hooked a UIButton to a storyboard segue action (in IB) but later decided to have the button programatically call performSegueWithIdentifier forgetting to remove the first one from IB.
In essence it performed the segue call twice, gave this error and actually pushed my view twice. The fix was to remove one of the segue calls.
Hope this helps someone as tired as me!
Swift 5
func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
//Delete or comment the below lines on your SceneDelegate.
// guard let windowScene = (scene as? UIWindowScene) else { return }
// window?.windowScene = windowScene
// window?.makeKeyAndVisible()
let viewController = ListVC()
let navViewController = UINavigationController(rootViewController: viewController)
window?.rootViewController = navViewController
}