I was scratching my head wondering why my rvc was set to nil when watching it while debugging through Xcode and thinking there must be something wrong with my project. So I created a project from scratch using the Xcode single view app template and then the only change I made was to add the following lines to didFinishLaunchingWithOptions:
Now look at what Xcode is displaying for the value of rvc in the watch window:
What's going on, why is it reporting rvc is nil?
Its not actually nil, but Xcode's watch window is reporting it as such. Is this a known issue with Xcode?
I found out the problem - its the positioning of the breakpoint, position it a line higher and rvc is not nil.
If you look at the watch window you can see rvc is light text when the other variables are bold text.
So my conclusion is at that point Xcode is reporting that rvc has gone out of scope and been deallocated, yet as the return statement has not yet executed at that point then rvc should not yet have gone out of scope.
Is it some Objective-C optimization thing going on resulting in this in Xcode or is it a defect with Xcode?
Either way its wasted a few hours of my time thinking I had a problem when there wasn't. In the future I need to make sure never to position breakpoints on a return statement again that contains local variables.
Related
i am making a very complicated app with a lot of classes.
my app worked great and i worked on it for the last month.
the last time i worked on it i added a function and it worked great, i saved the app and ran it a few times since and it worked. the last time i turned my computer on, it prompted me that an update for xcode is available. i updated it, and since then every time i run my app it runs with no errors but on ios simulator it shows a black screen. what can i do? i worked really hard on that app. thanks for the help in advance.
There's few issues that could happened, withou detailed description of this issue, you can try following solutions:
reset simulator
check if your initial controller is set up in storyboard(select controller and press attribute inspector, select is initial view controller):
if you're setting initial view controller programmatically, check if that controller is not nil in app delegate
another tip - try to use UI debugger, that helps a lot:
Any debug messages in the Xcode output? That usually will give a clue.
One thing I can think of, is that in your
- (void) applicationDidFinishLaunching:(UIApplication*)application
delegate, try setting the window's root view controller to your view controller. Example:
[window setRootViewController:viewController];
[window makeKeyAndVisible];
Again, the Xcode debug output will confirm if this is indeed the case though.
I'm coding a video processing app and was just about to submit it to the app store when ios 8.1 came out. I updated my iPhone as well as XCode and all hell broke loose. In my simple single viewcontroller interface nothing is rotating anymore except for the statusbar, which also doesn't get automatically hidden anymore in landscape mode...
I figured it was because I was using the deprecated willAnimateRotationToInterfaceOrientation: for what little custom rotation actions I had, so I implemented traitCollectionDidChange: and viewWillTransitionToSize: to specs instead. However viewWillTransitionToSize never gets called in my app and traitCollectionDidChange: is only called once, at startup. The device simply isn't telling the app that the device has rotated.
After googling I've also tried using name:UIDeviceOrientationDidChangeNotification. At least my selector does get called for that one but I don't know how to manually handle all rotation.
My didFinishLaunching... and viewDidLoad are very simple. alloc UIWindow, storyboard, set my viewcontroller from there, make it rootviewcontroller, makekeyandvisible. All based on one of Apple's AVFoundation demo apps.
Then in didload I add some subviews and a toolbar etc, nothing out of the ordinary and obviously it did work on 8.0 and 8.0.2 on all kinds of devices as well as the 7.1 simulator etc. Still runs flawlessly on my iPad with 8.0.2... Reason I haven't posted any code is I'm 100% sure everything is correct on that end.
Main weird thing is I can't seem to find anyone with this problem.
No errors in console or elsewhere either.
Does anyone have any idea of what might be causing this? I didn't think a point release would make such massive differences and again, no one else seems to be having this. Could it be an issue/bug in the actual storyboard file?
And, mainly, since I can get rotation notifications through UIDeviceOrientationDidChangeNotification, how do I manually handle all rotation/resizing stuff? I have been looking all over for answers but to no avail and am out of time to spend on this project currently :(
Cheers!
alloc'ing UIWindow will be the problem.
First, Make sure your navigation controller (or whatever you're using) is set as "Initial View Controller" in your storyboard.
Secondly, in your AppDelegate.m file, remove any references to UIWindow and rootViewController that appear in application didFinishLaunchingWithOptions. In my case, removing the following two lines fixed my issues.
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
[self.window makeKeyAndVisible];
You also don't need to set the window's rootViewController if using storyboards.
They're simply not needed when using storyboards, but until 8.1 there was never any harm using them. It took my 2 days to figure this out, so hopefully it will help you and others too.
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.
I have an iPhone app, that seems to have memory leaking problem. It's a puzzle game, after a few puzzles, the app crashes on devices.
I'm now trying to use xcode Instruments to detect what's going on. First time to use Instruments.
I noticed a leak bar in the "Leaks" plot, right the time when the view is loaded:
What are these memory leaking objects, detected by xCode Instruments?
. However these leaked objects are small, so I guess my app has other problems.
When my app continues to run, usually for 10+ rounds on an iPad 2, it then crashes. I don't much about Instruments yet, so I watch "All Heap Allocations". At the beginning of first round puzzle, the column "# Overall" is ~70k, it grows slowly between rounds of puzzles. When a new round puzzle comes in, it goes to ~90k, then round by round it reaches ~200k, then crashes.
Before crashes, in the log console I see memory warning and "CONNECTION INTERRUPTED".
I've followed a few things after searching memory leaking, such set NSArray/NSDictionary or mutable ones to nil, as much as possible (although not all of them, since some go between puzzles). I also changed UIImage imageNamed to [UIIMage alloc] initWithContentOfFile.
What else should I look/check to see what causes memory problem? TIA!
EDIT:
I wish I could post some codes that may be the suspect, but I really don't know what part to post. I should've check via Instruments in the course developing, so that I would know what caused the problem.
Regarding other view controllers. I do have others (menu, settings, app-store-rate, etc) and I generated all of them via code. My app doesn't have a storyboard or nib file. When I test crashes, I just click Next Puzzle button, so all other views will not show at all. So, before crash, the only view shown is the main view, with a few button, a few subviews, an animated pictures (but only the first puzzle as introduction). If it helps, here is my app:
http://itunes.apple.com/us/app/wordsect/id599455449?ls=1&mt=8
If you trying to debug application with Instruments - enable zombie detection mode:
In
Xcode: Product->Scheme->Edit Scheme
Select Debug scheme
Select Arguments tab bar on the scheme description
In Environments variables add and check NSZombieEnabled variable
Then when you start application under Instruments control, you'll get name of the instance, when your application crashed.
i'm currently working on an ios project with some people, one of us decided to use ARC in a part of the app.
Unfotunatly, we are currently experiencing some crashes when coming back from background.
Here are the steps we follow to crash the application, we perform them with the ios-simulator:
start the application
get on a ViewController A (coded with ARC)
get on a ViewController B (not coded with ARC -to be honest i don't
know if it's relevant-)
put the application in background.
simulate a memory warning (thx to the simulator)
start again the application, we'll be on the ViewController B
go back on the Viewcontroller A
the application crashes pointing the main function with an
EXC_BAD_ACCESS
We did try to use NSZombieEnabled to YES, but when we do it, the application doesn't crash and keeps running perfectly, so we wonder if it might be possible that NSZombieEnabled doesn't work well with ARC?
if anyone could give me a quick and clear insight about ARC and NSZombieEnabled that would be apreciated, i think i know how all of it works, but apparently i must be missing something.
Thanks anyway for your help and time.
Better than using the NSZombieEnabled, you should Profile the project, and use the Zombie instrument. When you do the same thing it should stop and say "zombie messaged", where you can click an arrow to see the class that is a zombie, and where it was allocated/deallocated.
I don't think the crash has to do with ARC, instead in viewDidUnload you are deallocating something, and then not setting a reference to nil - when you come back it tries to use the invalid reference.
Probably you would be better off if everything used ARC as it really helps to cure issues like this (the bug is very likely in the non-ARC code).