I'm getting an odd error. We are using iOS 5 with ARC. When NSZombiesEnabled is set to true and the app is plugged into the debugger we get this error (it happens normally too but not as consistently)
2012-07-04 11:25:17.161 Trivial[624:707] -[vcCurrentGames gamesLoaded:] [Line 284] Found 62 games that are my turn.
2012-07-04 11:25:17.162 Trivial[624:707] -[vcCurrentGames gamesLoaded:] [Line 285] Found 26 games that are their turn.
2012-07-04 11:25:17.169 Trivial[624:707] -[vcCurrentGames tableView:heightForHeaderInSection:] [Line 409] Height 1: 29
2012-07-04 11:25:17.171 Trivial[624:707] *** -[vcDashboard retain]: message sent to deallocated instance 0xf62c3c0
We are not retaining the dashboard anywhere (ARC doesn't allow retain). This only happens after the app is loaded from the background. vcCurrentGames is actually a UITableView on the dashboard. Which makes it even more odd to me, because if the dashboard is dealloced then why is it's UITableView loading?
I've read a little bit about this. The dashboard is defined in the app delegate as a property:
#property (nonatomic, strong) vcDashboard *vDashboard;
I've attempted making this weak so that it will zero out, but that doesn't work either. Can someone tell me why it's being dealloced or why it's trying to retain vcDashboard after it's been dealloced?
In app delegate I declare it like this:
UIViewController *viewController = [[vcDashboard alloc] initWithNibName:#"vcDashboard" bundle:nil];
self.vDashboard = (vcDashboard *)viewController;
Maybe something goes wrong during initialization. You assign the vcDashboard to a UIViewController and then cast that controller to the appropriate class. While theoretically this should be fine, I have never seen this pattern before. The standard way is:
self.vDashboard = (vcDashboard*) [[vcDashboard alloc] init];
assuming that the nib name is "vcDashboard" (as seems to be the case) and that the class in the nib is also "vcDashboard".
(BTW, the convention is to capitalize class names.)
Also, after the app goes into the background, maybe vcDashboard gets deallocated. In any case, it is not guaranteed that it is still there when the app comes back from background. Did you consider lazy instantiation?
// in app delegate
-(vcDashboard*)vDashboard {
if (_vcDashboard) {
return _vcDashboard;
}
vcDasboard vc = [[vcDashboard alloc] init];
// more initialization code
_vcDashboard = vc;
return vc;
}
Related
I come from a C/C++ background and am currently learning a bit about Cocoa and Objective-C.
I have a weird behavior involving lazy initialization (unless I'm mistaken) and feel like I'm missing something very basic.
Setup:
Xcode 10.1 (10B61)
macOS High Sierra 10.13.6
started from a scratch Cocoa project
uses Storyboard
add files TestMainView.m/.h
under the View Controller in main.storyboard, set the NSView custom class as TestMainView
tested under debug and release builds
Basically, I create an NSTextView inside a view controller to be able to write some text.
In TestMainView.m, I create the chain of objects programmatically as decribed here
There are two paths:
first one is enabled by setting USE_FUNCTION_CALL to 0, it makes the entire code run inside awakeFromNib().
second path is enabled by setting USE_FUNCTION_CALL to 1. It makes the text container and text view to be allocated from the function call addNewPage() and returns the text container for further usage.
First code path works just as expected: I can write some text.
However second code path just doesn't work because upon return, textContainer.textView is nil (textContainer value itself is totally fine).
What's more troubling though (and this is where I suspect lazy init to be the culprit) is that if I "force" the textContainer.textView value while inside the function call, then everything works just fine. You can try this by setting FORCE_VALUE_LOAD to 1.
It doesn't have to be an if(), it works with NSLog() as well. It even works if you set a breakpoint at the return line and use the debugger to print the value ("p textContainer.textView")
So my questions are:
is this related to lazy initialization ?
is that a bug ? is there a workaround ?
am I thinking about Cocoa/ObjC programming the wrong way ?
I really hope I am missing something here because I cannot be expected to randomly check variables here and there inside Cocoa classes, hoping that they would not turn nil. It even fails silently (no error message, nothing).
TestMainView.m
#import "TestMainView.h"
#define USE_FUNCTION_CALL 1
#define FORCE_VALUE_LOAD 0
#implementation TestMainView
NSTextStorage* m_mainStorage;
- (void)awakeFromNib
{
[super awakeFromNib];
m_mainStorage = [NSTextStorage new];
NSLayoutManager* layoutManager = [[NSLayoutManager alloc] init];
#if USE_FUNCTION_CALL == 1
NSTextContainer* textContainer = [self addNewPage:self.bounds];
#else
NSTextContainer* textContainer = [[NSTextContainer alloc] initWithSize:NSMakeSize(FLT_MAX, FLT_MAX)];
NSTextView* textView = [[NSTextView alloc] initWithFrame:self.bounds textContainer:textContainer];
#endif
[layoutManager addTextContainer:textContainer];
[m_mainStorage addLayoutManager:layoutManager];
// textContainer.textView is nil unless forced inside function call
[self addSubview:textContainer.textView];
}
#if USE_FUNCTION_CALL == 1
- (NSTextContainer*)addNewPage:(NSRect)containerFrame
{
NSTextContainer* textContainer = [[NSTextContainer alloc] initWithSize:NSMakeSize(FLT_MAX, FLT_MAX)];
NSTextView* textView = [[NSTextView alloc] initWithFrame:containerFrame textContainer:textContainer];
[textView setMaxSize:NSMakeSize(FLT_MAX, FLT_MAX)];
#if FORCE_VALUE_LOAD == 1
// Lazy init ? textContainer.textView is nil unless we force it
if (textContainer.textView)
{
}
#endif
return textContainer;
}
#endif
- (void)drawRect:(NSRect)dirtyRect {
[super drawRect:dirtyRect];
// Drawing code here.
}
#end
TestMainView.h
#import <Cocoa/Cocoa.h>
NS_ASSUME_NONNULL_BEGIN
#interface TestMainView : NSView
#end
NS_ASSUME_NONNULL_END
I am not familiar with cocoa that much but I think the problem is ARC (Automatic reference counting).
NSTextView* textView = [[NSTextView alloc] initWithFrame:containerFrame textContainer:textContainer];
In the .h file of NSTextContainer you can see NSTextView is a weak reference type.
So after returning from the function it gets deallocated
But if you make the textView an instance variable of TestMainView it works as expected.
Not really sure why it also works if you force it though. ~~(Maybe compiler optimisation?)~~
It seems forcing i.e calling
if (textContainer.textView) {
is triggering retain/autorelease calls so until the next autorelease drain call, textview is still alive.(I am guessing it does not get drained until awakeFromNib function returns). The reason why it works is that you are adding the textView to the view hierarchy(a strong reference) before autorelease pool releases it.
cekisakurek's answer is correct. Objects are deallocated if there is no owning (/"strong") reference to them. Neither the text container nor the text view have owning references to each other. The container has a weak reference to the view, which means that it's set to nil automatically when the view dies. (The view has an non-nilling reference to the container, which means you will have a dangling pointer in textView.textContainer if the container is deallocated while the view is still alive.)
The text container is kept alive because it's returned from the method and assigned to a variable, which creates an owning reference as long as that variable is in scope. The view's only owning reference was inside the addNewPage: method, so it does not outlive that scope.
The "force load" has nothing to do with lazy initialization; as bbum commented, that it "works" is most likely to be accidental. I strongly suspect it wouldn't in an optimized build.
Let me assure you that you do not need to go around poking properties willy-nilly in Cocoa programming. But you do need to consider ownership relations between your objects. In this case, something else needs to own both container and view. That can be your class here, via an ivar/property, or another object that's appropriate given the NSText{Whatever} API (which is not familiar to me).
I'm getting some weird behavior, I Set a Label in Interface Builder, then I connect the label to a file as an Referencing Outlet.
#property (weak) IBOutlet NSTextField *TitleLabel;
When I access that label in the file (cell.TitleLabel.stringValue = title) and run the application, it doesn't recognize it.I get this:
-[NSApplication TitleLabel]: unrecognized selector sent to instance 0x608000101680
The weird thing is that it doesn't always do this, sometimes it works and displays correctly, other times it doesn't.
I've just started messing with IB so I'm probably missing something. Any help?
Is the property really on your NSApplication subclass? or is it on you application delegate class? It's not impossible for it to be on the application object, but it would be a pretty uncommon (and arguably ill-advised) pattern.
In short, I suspect you're probably connecting it to the wrong object.
EDIT: Ah. I see. You're trying to access things via the topLevelObjects array, but in practice, you can't count on the order of topLevelObjects. What you need to rely on the owner's outlets getting populated, but you're passing nil for the owner. topLevelObjects only exists to give the caller "ownership" (in the reference counting sense) of the top level objects in the xib for memory-mangement purposes, it's not really meant to be "used" directly like you're doing here. (In fairness, I can imagine situations where you might need to introspect that array, but this hardly rises to that level.)
The canonical way to do this would be to use an NSViewController subclass as the owner. In Xcode, if you add a subclass of NSViewController to your project, it will give you the option to create a xib file at the same time that will have everything hooked up. Then you just initialize the NSViewController subclass at runtime and the view outlet property of that class will be filled with the root view. You can obviously add more outlets and plug in whatever you like.
This post appears to cover the basics, if your looking for more details. Apple's docs on xib files and how they work are here.
The problem was that the View would sometimes get assigned to NSApplication. I'm not sure if the way that I am initiating the view is the common way of doing it but the problem was within this block of code:
NSArray * views;
[[NSBundle mainBundle] loadNibNamed:#"CollapseClickViewController" owner:nil topLevelObjects:&views];
CollapseClickCell * cell = [[CollapseClickCell alloc] initWithFrame:CGRectMake(0,0,320,50)];
cell = [views objectAtIndex:0];
the problem was that [views objectAtIndex:0] would sometimes return NSApplication. To fix it I just checked the class against itself and returned that object via:
-(CollapseClickCell*)assignCell:(CollapseClickCell*)cell withArray:(NSArray*)array{
for ( int i = 0; i< [array count]; i++) {
if ([[array objectAtIndex:i] class] == [CollapseClickCell class]) {
return [array objectAtIndex:i];
}
}
return nil;
}
I then assign that to the object:
cell = [cell assignCell:cell withArray:views];
It may not be the conventional way of doing it but it works. If there is a better technique or a more common approach please enlighten me! :)
I'm seeing some disturbing irregularities concerning object allocation and initialization in an app I'm trying to write.
I have a 'root' Modelcontroller object, which in turn contains references to subcontrollers. The root controller is called modelController, and in it's init method it allocates and inits the subcontrollers like so:
- (id)init
{
NSLog(#"%#", #"ModelController begin init");
self = [super init];
if (self) {
LibraryController * tempLibrary = [[LibraryController alloc] init];
self.library = tempLibrary;
StoresController * tempStores = [[StoresController alloc] init];
self.stores = tempStores;
CLLocationManager * tempLocationManager = [[CLLocationManager alloc] init];
self.locationManager = tempLocationManager;
}
NSLog(#"%#", #"ModelController complete init");
return self;
}
Pretty standard. The subcontrollers' init code also contain an NSLog messages at the beginning and the end, for me to be able to see that all is well.
The properties are defined as
#property (strong) LibraryController * library;
#property (strong) StoresController * stores;
#property (strong) CLLocationManager * locationManager;
And I am using ARC.
What puzzles me is that sometimes I see the NSLogs from one of the subcontrollers, but not from the root controller. Sometimes I see the 'begin init' log message from the root controller, but not the 'complete init'. Sometimes I see no init log messages. The application launches anyway in any of these cases.
This happens seemingly at random, in one out of five launches or in one out of twenty launches. When it happens, the app acts very strange (but not every time, mind you), beachballing for no apparent reason and exhibiting general wonkiness.
As a side note, at one time I put a breakpoint in the init method of the StoreController class, which when pausing executing spit out a chunk of random data in the debugging console:
$m2303,3503,3603,3703,3803,3903#00$m2303,3503,3603,3a03#00$88ee410901000000981e420901000000001e42090100000060ee410901000000b062f668ff7f000070044391ff7f0000f00e0800000000000300000068200100dc62f668ff7f0000d862f668ff7f00000000000000000000717ddd8aff7f00000000000068200100801e420901000000000000000600000706000007000000007063f668ff7f000003280000000000007863f668ff7f000001ee410901000000f062f668ff7f00006c5bd391ff7f000000000000ff7f0000ab064391ff7f000000000000ffffffff032800000000000040
...and so on
Where should I begin to look to troubleshoot this?
The modelController is alloc init'd from the MyDocument equivalent class, and is modeled as a singleton.
The singleton implementation looks like this:
static ModelController *sharedModelController = nil;
+ (ModelController*)sharedManager
{
if (sharedModelController == nil) {
sharedModelController = [self new];
}
return sharedModelController;
}
Final note: I have tried removing the locationManager stuff and disabling/enabling the 'Restore state' preference in the scheme, but to no avail.
Sounds like you're doing some UI stuff not on the main thread.
This generally leads to weird behavior.
Make sure you call everything UI related on the main thread
Best guess: the ModelController object is being released. Perhaps the Singleton is faulty.
have a problem with object setters in a class.
I have the class GEOImage, where things like description, title etc. will be saved according
to an image.
#interface GEOImage : UIImage
{
NSString *title;
NSString *imgDescription;
NSString *latitude;
NSString *longitude;
NSDictionary *editInfo;
}
#property (nonatomic, copy) NSString *title, *imgDescription, *latitude, *longitude;
#property (nonatomic, copy) NSDictionary *editInfo;
#end
Now i try to store a description out of another class:
self.chosenImage.imgDescription = #"description";
where chosenImage is of type GEOImage.
But i get the error:
-[UIImage setTitle:]: unrecognized selector sent to instance 0x939d220
2011-12-05 10:59:40.621 GeoPG[511:17c03] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIImage setTitle:]: unrecognized selector sent to instance 0x939d220'
If I'm looking in the debugger, the chosenImage is not NULL, and its been displayed correct in an image view.
Greets
s4lfish
We can safely infer that chosenImage is not nil; if it were nil, sending it a message would simply do nothing, not crash.
(Also, I'm assuming that you meant title rather than imgDescription in your usage sample, or that you implemented setImgDescription: to set the title in turn.)
There are two possibilities:
Dead object
You created the image you stored to chosenImage as a GEOImage, but then it died while you were holding on to it. Subsequently, a UIImage (as identified in the exception message) was created at the same address, so the pointer you still hold now points to a UIImage. You sent a message to it that only works on GEOImages, but it's only a UIImage, so it doesn't respond to the message, which is the exception.
The cause of an object dying while you're holding it is that either you didn't retain it somewhere where you should have, or you released it somewhere where you shouldn't have. Or possibly both.
Run your app under Instruments with the Zombies template. It will raise a flag when you hit this crash, and you can then investigate by clicking the button in that flag. Look at all of the Release and Autorelease events, starting from the end, to find the one that shouldn't be there; then, if the release itself is unwarranted, take it out, or if it should be balanced by a previous retain, put one of those in.
One possible cause of the crash is that you declared the chosenImage property as assign, but you should have declared it as retain/strong. If this is the problem, your Instruments findings will support it.
Long-term, you should convert to ARC, which eliminates 90% of the cases where this problem could happen.
You never created a GEOImage in the first place
Just because you declared that chosenImage will hold a pointer to a GEOImage doesn't mean it does. You can assign any object pointer there, and in many cases, the compiler doesn't know if it isn't actually a GEOImage.
(They introduced a feature called “related result types” in a future version of Clang that should make this much less likely.)
At a guess, I'd say you're doing something like this:
self.chosenImage = [GEOImage imageNamed:#"blah blah blah"];
or this:
self.chosenImage = [imagePicker takePicture];
There is no reason to expect takePicture to return a GEOImage (how should it know that's what you want?), and it's likely that +[UIImage imageNamed:] (assuming you simply inherit it) won't, either. Unless you create a GEOImage instance yourself, using alloc and an initializer, you cannot assume that any UIImage you get will be a GEOImage.
The solution is to make it easy to create a GEOImage from a UIImage (which will involve wrapping this method), and then do that.
Once you have a live (not dead) GEOImage (not UIImage) in your chosenImage property, it will work.
In fact, it was like Peter said: I never created an GEOImage. I now I create the GEOImage like this:
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
UIImage *image = [info valueForKey:#"UIImagePickerControllerOriginalImage"];
NSURL *imgURL = [info valueForKey:#"UIImagePickerControllerMediaURL"];
CGImageRef imageRef = [image CGImage];
[self createGEOImage:imageRef info:info imageURL:imgURL];
}
And the method called with the imageRef:
- (void)createGEOImage:(CGImageRef*)imageRef info:(NSDictionary*)info imageURL:(NSURL*)imgURL{
GEOImage *geoImage = [[GEOImage alloc]initWithCGImage:imageRef];
geoImage = info;
geoImage = imgURL;
}
Thanks for your help!
In a method I wrote, I'm declaring an instance of class 'A' and calling a method on it. At run time, when the method runs, my app crashes. It says an unrecognized selector was sent to an instance of class 'B' even though I declared an instance of 'A'. I read somewhere that I may not be managing my memory correctly so it's sending the method to another class, but I'm using ARC so that shouldn't even be a problem. Help would be much appreciated!
The error I'm getting:
2011-08-27 01:25:49.859 Intelligenda[49385:bc03] PVC: <HomeViewController: 0x59359e0>
2011-08-27 01:25:49.945 Intelligenda[49385:bc03] -[HomeViewController addNewClass:]: unrecognized selector sent to instance 0x59359e0
2011-08-27 01:25:49.947 Intelligenda[49385:bc03] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[HomeViewController addNewClass:]: unrecognized selector sent to instance 0x59359e0'
and the method that's being called:
-(IBAction)done:(id)sender{
[teacherName resignFirstResponder];
[className resignFirstResponder];
IntelligendaAppDelegate *delegate = [[UIApplication sharedApplication] delegate];
UINavigationController *nav = delegate.navController;
[nav popViewControllerAnimated:YES];
ClassesViewController *classesParentViewController = (ClassesViewController *) nav.topViewController;
ClassIG *theNewClass = [[ClassIG alloc] init];
theNewClass.className = className.text;
theNewClass.teacherName = teacherName.text;
NSIndexPath *indexPath;
theNewClass.subject = [tableView cellForRowAtIndexPath:indexPath].textLabel.text;
// add reminder to array
NSLog(#"PVC: %#", [classesParentViewController description]);
[classesParentViewController addNewClass:theNewClass];
}
Declaring, say, a pointer NSArray* fred does nothing (other than a sprinkling of compile-time warning messages) to assure that fred is an NSArray. It's what you assign to fred that counts. If you assign an NSDateFormatter, then that's what fred is.
Your assumption that the application delegate's navigation controller has a ClassesViewController on top is clearly flawed. It has a HomeViewController on top. Your structure looks like it may be a little complicated, given that you have a button somewhere wired up to an action in some other part of your controller classes, so there could be a bunch of causative reasons.
First things to check: if you're instantiating buttons programmatically then did you accidentally add the button to the wrong controller? If you're designing everything using the graphical interface designer but keeping it in a single NIB, is it possible you copied and pasted a button and forgot to change what it's wired to?
If you can end up with multiple navigation controllers, are you sure the one held by the application delegate is currently on screen?
the short answer is that typecasting and type conversions are an exercise for the programmer in objc.
read my answer here:
Passing NSNumber* to NSString* expected-parameter does not cause compiler warning / error
...for some more information as to how declaring/casting a variable of an object differs from other languages, and how you can detect those cases.