I'm new to using a mac and iOS development. Today I followed this tutorial on to a how to bind data to a table view by making use of Prototype cells and the Story Board. I've got up to the part of the tutorial where I should be able to run the app so the bound data shows up in the UITableView like this:
My app compiles fine, but as soon as it starts running it hits a runtime error:
[ViewController viewControllers]: unrecognized selector sent to instance
I have tried going through the tutorial several times now. I've followed the tutorial exactly as it says and have even created 3 different projects from scratch to make sure that nothing is going wrong. Can anybody help me fix the error? I've spent hours trying to work out what's going wrong, and I don't want to give up now as iOS development seems so exciting compared to other platforms!
Unrecognized selector means that there is an undefined method being called.
One thing to do is to see if there are any compiler warnings. Does it give you any? Have a look, it may give you a clue what is undefined.
The tutorial refers to ViewController class. It looks like that this class is used briefly at the start of the tutorial but then it is replaced with another class. You may remove this class later on altogether. Check if you wire tab bar controller properly. have you set it to be "an entry point"?
Check the storyboard. Where does an incoming arrow point to? Compare two images below. First has the entry arrow pointing to ViewController (my guess), second - the arrow point to Tab Bar Controller
.
At some point (without the code is hard to tell where) you are getting a reference to a ViewController, treating it as a UITabBarViewController.
viewControllers is a method of UITabBarViewController but you are invoking it on a ViewController.
You probably have something like
UITabBarViewController *tabBarVC = (UITabBarViewController *)[something aMethod];
tabBarVC.viewControllers...
So it compiles fine, but it rightfully crashes at runtime.
Related
The app crashes in AppDelegate, unable to get beyond the launch screen. No view controller code ever gets executed.
The stack trace is also not very helpful nor is the line highlighted in AppDelegate when the crash occurs.
Images below provide the details.
How to debug from here?
Check any IBOutlet links carefully; you may have deleted the property from your view controller but the UI element is still connected to it. This should give you an exception stating something like Class ViewController is not key value coding-compliant for key XXX where XXX is your bad IBOutlet, however Swift's exception reporting does seem to be a bit hit-and-miss at times.
Here's another possible cause related to the reason Paulw11 stated that may help someone else.
If you have segue's in your storyboard that links to a storyboard reference in another bundle, and you change the name of the bundle where the reference resides, make sure to update the Bundle name in your storyboard for the linked reference.
I have a framework I'm developing that contains some storyboards and UI components. I decided to rename the framework, updated the podfile references in the app and all the file imports to reflect the new framework name but completely forgot that there were storyboard references in the app referencing view controllers provided in storyboards in the framework.
Here's an example:
If you do not rename the reference you will experience a crash when you try to load the storyboard containing your link with no hint as to why. I spent an embarrassing amount of time hunting this down.
I have recently started to learn iOS with obj-c from "iOS Programming The Big Nerd Ranch Guide 4th Edition". This edition was released in 2014 and is written with Xcode 5.
I am trying to make a simple app with two buttons and two labels. The labels are connected to two arrays and when a button is pressed an object from the corresponding array is shown in the corresponding text label (it's the Quiz app in chapter 1).
I created the project as a Single View app in Xcode 6, and put all my objects in the view controller class. I have two labels two buttons two arrays and an int to keep track of the object that has to be displayed from the array.
In the book it says that I should initialize the arrays in the initWithNibName method. I tried that but for some reason it never gets called. So I changed the initialization of the arrays to the init method. They initialize fine but when they are called from another method they are nil. Do you have any idea why this is happening?
The second issue I'm having is that I can't manage to get the contents of the storyboard on screen. It says that I'm supposed to make an instance of the ViewController inside the AppDelegate and make it the root window controller but all I get is a white window (or black in case I don't set the color).
UPDATE: I changed the intialization of the arrays from the init method to the viewDidLoad method and now they seem to be working fine. Nothing on the screen though.
It sounds like you're initializing your UIViewController from the app delegate AND a storyboard. If you create a new project in XCode, a "Single view application", you won't have to touch the app delegate at all in order to get something on the screen.
I believe both your problems are related to this, since it sounds like you're seeing an empty UIViewController on the screen (the one you create in the app delegate)
As for the initialization of your array, viewDidLoad is a popular place to do this.
If you are using storyboards, the method initWithNibNameOrNil will not be called. In the BNR book, it teaches you to use XIB files, which do use this method. If you are trying to follow the tutorials, I would suggest using XIB files.
For use of a book, I would suggest downloading whatever version of Xcode is being used for that book -- otherwise you will be running into a lot of confusing problems while learning.
If you would like to download previous version of Xcode, refer to this post:
How to download Xcode DMG or XIP file?
I have a UITextView, and whenever I click on it, the app crashes with the following error:
-[__NSSetM _hideForKeyboardAppearance]: unrecognized selector sent to instance 0x7fb8aa76cd60
If I run the app multiple times, it always crashes at the same place, but the intercepting object that is throwing the "unrecoginzed selector" can be different. Sometimes it is UIImage instead of NSSetM, sometimes, it is a UIConstraint, etc.
Even if I don't assign the UITextView to a specific outlet in my class, or have it assigned to a delegate, I get the same behavior. This happens on both simulator and hardware.
Any ideas what is going on?
p.s. this is iOS 8. Crash happens on both iPhone and iPad.
Edit: Note that this happens even though the UITextView calls no code. I removed any outlet connections in the storyboard, and even made it so my class doesn't implement UITextViewDelegate. Still crashes. That is why I am so puzzled and wondered if anyone has ever encountered something like this. One thing to note is that the view controller having this issue is buried several screens deep within a UISplitViewController. Not sure if someone UI elements buried deep in the nav stack are somehow intercepting the keyboard call?
My app crashes randomly when navigating back in a NavigationController. Here is what I know:
It happens randomly (sometimes, I can come back once or twice and if I reload the viewController and press "back" again it will crash)
It happens even with an empty ViewController (I tried to comment out all my code in ViewController.h and .m and to remove all the outlets links)
Nothing shows up in the debug console, only a EXEC_BAD_ACCESS is shown in main.m
I spent the afternoon on this and tried everything.
I don't include code right now because I have no idea where to look. As I said, it even happens with an empty ViewController.
Any thoughts or similar experience ?
EDIT:
Yes I tried to add an exception breakpoint
I even tried to find some observer issues with Spark debugger.
EDIT 2:
Actually, the ViewControllers were not that empty. The import on an UIView category was the problem. Check my answer below.
It's difficult to say exactly what could be causing it without more information, but in my experience the most common reason for an EXC_BAD_ACCESS is when someone tries to call a selector on a deallocated instance. This issue can be a lot easier to debug if you enable zombie objects.
Edit Scheme -> Diagnostics -> Enable Zombie Objects
Now instead of getting a bad access exception you should get a more helpful "message sent to deallocated instance" error (assuming that's actually the problem), along with what method was being called on which class of object.
The problem was that some of my views were importing a custom UIView category that included a dealloc method. I deleted the dealloc method from the category and everything is fine now.
I have an iPad app that has been running fine until iOS7. This issue seems to be only on ipad 2nd gen models and earlier when iOS7 is installed. Anyway, I've been tearing my hair out trying to figure out where this error is coming from, but have had no luck. The console in xcode (5) reports the following error after I perform a logged in segue:
2013-11-18 11:17:31.768 MyApp[400:60b] *** -[UIToolbar backdropView:willChangeToGraphicsQuality:]: message sent to deallocated instance 0x18ec23e0
I can't lookup the address for more info (image lookup -a 0x18ec23e0) it just returns nothing.
In instruments running zombies, it reports that a message was sent to a UIToolbar like so:
When I inspect the instance, I get the following:
How do I debug this? I have no idea where this call is being made and it seems dependent upon a physical deivce (doesn't happen on the iPad mini or ipad 3/4)
I was struggling with a very similar error, also with a UIToolbar, that I couldn’t figure out until a couple hours ago. I also had to use and try to understand the zombies’ instrument but without any luck.
What I did was to pay a close attention to the call stack that was presented when the Exception Breakpoint was activated as described in the following tutorial:
http://www.raywenderlich.com/10209/my-app-crashed-now-what-part-1
Even though the call stack didn’t point me to the exact code line, I noticed that the app was trying to add a UIToolbar to a ViewController. Turns out that what I was doing was creating a local UIToolbar inside of a method and adding it to the presented UIView. After have modified this behavior, I stopped having the annoying sudden crash. It was difficult for me to find the issue because looking at the code of the ViewController that caused the crash, there was no code that created or used a UIToolbar; however this VC included a custom view that did exactly that, as I explained before.
Have said all of this I recommend you to closely inspect the VC that generates the crash. If you need to create a UIToolbar programmatically I recommend you to declare it as a strong property to maintain the memory reference as long as needed.
I hope this helps you.
I struggled with this for a while today. I had two storyboards, one for login/signup (set as the main storyboard for the project) and another with the rest of the application. The app delegate would detect if a user was logged in and instantiate the root view controller of the other storyboard. The root view controller of the login storyboard is a navigation controller and after after some investigation with instruments I realized there was a UIToolbar being instantiated from the nib. Opening up the storyboard file revealed an off-screen UIToolbar object in the root view controller. I deleted it and I'm not crashing any more.
I should also mention this crash was only occurring when I was using MKMapView.