UIScrollView loses reference to delegate - ios

I need to create a number of UIScrollViews dynamically and fill them with content. This is all good except when i set the delegate to self and pan the list i get this exception:
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString scrollViewDidScroll:]: unrecognized selector sent to instance 0x7581230'
NSCFString obviously isn't my view controller (which implements the protocol UIScrollViewDelegate) so from what i gather somehow the memory gets messed up and it doesn't keep the reference correctly. Occasionally this can be something else too which strongly points to something being wrong with the memory
Here's the code to create the list:
for (NSUInteger i = 0; i < self.stories.currentStory.selectableWordCount; i++) {
UIScrollView *list = [[UIScrollView alloc] init];
list.alwaysBounceVertical = YES;
list.showsVerticalScrollIndicator = NO;
list.clipsToBounds = NO;
list.delegate = self;
list.pagingEnabled = YES;
[self.view addSubview:list];
.. // add UILabels to the list, set the frame, contentSize etc
[self.wordLists addObject:list]; // this is a #property (nonatomic, strong) NSMutableArray, declared in a private interface()
}
If i NSLog the delegate it's correct. respondsToSelector also matches fine. Interestingly if i comment out the scrollViewDidScroll: respondsToSelector: doesn't match any more and (probably because of this) the UIScrollView won't attempt to call this method any more. This then means that it can reach the delegate correctly to check for the method availability but when it gets called something goes wrong.
I'm targeting iOS5 with ARC. If this wasn't the case i would assume that i messed something up with the memory myself but now i don't have the same control.
I'm having a hard time debugging this issue, any help on how to proceed would be appreciated

D'uh. I was obviously looking in the wrong place. The view controller was added through a .xib and the view was pointing to a subview on the stage. However i needed to create an IBOutlet to the view controller in the main view controller to make sure it stays in memory. Hopefully this can help somebody else with a similar problem :)

Related

addChildViewController giving NSException error?

I am new to using this method so I could be doing this completely wrong so here is my code:
#property (nonatomic, weak) ConverterViewController *converterViewController;
#property (nonatomic, weak) CalculatorViewController *calculatorViewController;
If I am understanding this code correctly, these are acting as references to Two different ViewControllers.
Then I have this in my viewDidAppear method:
[self addChildViewController:_converterViewController];
[_converterViewController didMoveToParentViewController:self];
[self.view addSubview:_converterViewController.view];
I am getting an NSException at the first line when I try and add it as a child view controller. So not knowing whether or not this should then call some methods in my ConverterViewController class I put some breakpoints within that class both the initWithNibName and viewDidLoad methods and I found that neither of these methods are being called, so Im not exactly sure what is wrong. Then again Im not really sure what could go wrong so any help is greatly appreciated.
This is all I get from the console:
libc++abi.dylib: terminating with uncaught exception of type NSException
Updated Answer:
[self addChildViewController:_converterViewController]; does not create the converterViewController.
It simply takes the converterViewController object and adds it as a childViewController to self.
You will need to allocate memory and instantiate the object converterViewController before -addChildViewController: or else it's value will be nil and nothing will happen.
So... something this:
_converterViewController = [[ConverterViewController alloc] initWithNibName:#"ConverterViewController"
bundle:nil];
//now... adding it as childViewController should work
[self addChildViewController:_converterViewController];
[_converterViewController didMoveToParentViewController:self];
//optional: give it a frame explicitly so you may arrange more childViewControllers
//[_converterViewController.view setFrame:CGRectMake(0,0,100,100)];
[self.view addSubview:_converterViewController.view];

UIPicker View subclassed not working IOS

Being new to objective-C coding I started out writing a basic app, fully programmatically (not using storyboards or xib) in one file, my AppViewController h and m files.
Everything worked lovely.
So then I wanted to break up the mass of code by subclassing sections, and everything went well apart from the UIPickerView. In fact simply commenting out the [background addSubview:colorPicker]; seemed to totally fix the issue. I never found the answer online so I proceeded to make a new document to replicate said issue.
So here goes:
UIPickerViewController.h
#import <UIKit/UIKit.h>
#import "Picker.h"
#interface UIPickerViewController : UIViewController
#end
Simply imports my new class.
UIPickerViewController.m
#import "UIPickerViewController.h"
#interface UIPickerViewController ()
#end
#implementation UIPickerViewController
- (void)viewDidLoad
{
[super viewDidLoad];
UIView *superview = self.view;
int height = superview.bounds.size.height;
int width = superview.bounds.size.width;
CGRect popupRect = CGRectMake(0, 0, width, height);
UIView *popup = [[UIView alloc]initWithFrame:popupRect];
popup.tag = 8;
[superview addSubview:popup];
Picker *picker = [[Picker alloc]initWithFrame:popupRect];
[picker viewAddTypeScreenToView:superview];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
}
#end
Sets up a new view with a tag (so that i could reference it later with my new class)
Then actions a method from my new class to populate my new view.
Picker.h
#import <UIKit/UIKit.h>
#interface Picker : UIView
<UIPickerViewDataSource,UIPickerViewDelegate>
{
UIPickerView *colorPicker;
NSMutableArray *colorsArray;
}
#property (nonatomic, retain) UIPickerView *colorPicker;
#property (nonatomic, retain) NSMutableArray *colorsArray;
#property (strong,nonatomic) UILabel *myValue;
-(void)viewAddTypeScreenToView:(UIView*)superview;
#end
Setting up my variables and accessible method.
Picker.m
#import "Picker.h"
#implementation Picker
#synthesize colorsArray;
#synthesize colorPicker;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
}
return self;
}
-(void)viewAddTypeScreenToView:(UIView*)superview
{
UIView *baseView =[superview viewWithTag:8];
int height = baseView.bounds.size.height;
int width = baseView.bounds.size.width;
CGRect fullScreen = CGRectMake(0, 0, width, height);
UIView *background = [[UIView alloc]initWithFrame:fullScreen];
background.backgroundColor = [UIColor blackColor];
colorsArray = [[NSMutableArray alloc] initWithObjects:#"Red",#"Blue",#"Yellow",#"Green",nil];
CGRect myPickerRect = CGRectMake(10, 70, (width/2)-40, 200);
colorPicker = [[UIPickerView alloc]initWithFrame:myPickerRect];
colorPicker.dataSource = self;
colorPicker.delegate = self;
colorPicker.showsSelectionIndicator = YES;
[colorPicker selectRow:2 inComponent:0 animated:YES];
CGRect labelFrame = CGRectMake(10, 10, 180, 50);
_myValue = [[UILabel alloc]initWithFrame:labelFrame];
_myValue.textColor = [UIColor redColor];
_myValue.text = #"select colour";
[background addSubview:_myValue];
[background addSubview:colorPicker];
[baseView addSubview:background];
}
-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{
return 1;
}
-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component{
return colorsArray.count;;
}
-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
return colorsArray[row];
}
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
_myValue.text = [NSString stringWithString:colorsArray[row]];
}
#end
And finally the initiation called by the method in the picker class file.
This gives me an error along these lines
-[UITableViewCellContentView pickerView:titleForRow:forComponent:]: unrecognized selector sent to instance 0x8f2b000
2014-03-19 10:29:48.407 Briefcase[1800:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UITableViewCellContentView pickerView:titleForRow:forComponent:]: unrecognized selector sent to instance 0x8f2b000'
Which i've read is to do with either the datasource, or ARC systems, however none of the responses that I have found relate to or work with the type of set up that I have above. I'm sure it's something really simple but after a few days of failed searching, it's officially driving me crazy.
The problem is most likely that the instance of Picker that is being created in UIPickerViewController is never added to the view hierarchy and thus gets released prematurely (provided we're talking about a project using ARC here).
This leads to the pickerview's delegate and datasource becoming invalid and, basically, pointing at any random object. That's what is causing your crash: A message to your delegate cannot be delivered because the delegate is dead already. The picker still keeps a pointer which used to point at the delegate, but which has become invalid and points at a random object now, in this case a table view cell, which basically doesn't know what to do with this message and crashes.
The problem should go away if you add Picker *picker as an ivar or a retaining / strong property to UIPickerViewController.h - this will retain the picker beyond the scope of the viewDidLoad method and should keep it alive.
But that would be just a workaround, the real problem is your overall design. You said you're new to objective-c and indeed, it looks like you lack a basic understanding of iOS view and view controller hierarchies and, to some degree, the concept of object oriented programming. You might want to dig into something more basic before trying to fix your code because, quite frankly, it should be rather re-written than fixed.
I'd be happy to provide you with suggestions about how to structure your code, but please provide some information about what functionality you'd like to achieve first.
Edit (in response to your comment):
As a rule of thumb, do not spread functionality over several classes unless necessary. For objects, which serve a rather infrastructural purpose, like a specialized textfield or a pickerview, always ask yourself: "If I would like to reuse that object in another project, would that be as easy as using any other existing object, like, for example, UILabel?" If the answer is "No", then something is wrong. Ideally, interface objects are self-contained and to use them, you just invoke them, add them to a view and tell them, which text to display or which options to offer. If that information is subject to change or if the object needs to interact with other parts of your code, make use of delegation and protocols. Under no circumstances should the functionality of your object be tied to hard coded values or rely to some view to have a certain tag.
If you subclass UIView, the resulting object should behave like any other instance of UIView. It should be added to the view hierarchy by you or some object, but it shouldn't add or remove itself. If it works without being added to the view hierarchy at all, something is wrong. A view serves the purpose of being a part in your interface and all the logic it contains should work to that end, not more, not less.
Normally, interface objects should not interfere with one another. If something happens to one object (button pressed, option selected, text changed...) and another object is supposed to reflect that change, it is the view controllers responsibility to make that happen. The view controller is the place where the logic happens. If there is a task which requires a lot of complex logic, it might be a good idea to encapsule that logic into a purpose build class. One such example would be a class which manages network connections. This class should be again self contained: If the view controller needs some remote information, it asks your network class. Once your network class has that information (or failed to retrieve it), it reports back to your view controller. The view controller then updates the interface - under no circumstance should the networking class contain code which affects the interface.
It is important to understand that you could very well ignore these rules and still end up with a working app. And in some cases, the "direct" way may appear to be easier to implement and thus may look very tempting. But you'll pay the price later - once you start debugging your code. If your picker does not behave the way it should, you need to look into several places and wrap your mind around several objects, just to make one interface object behave right. And likely you will break one functionality while fixing the other.
So, try to make it right from the start, even though it requires more planning and learning. Trust me, it pays out, I started out just like you several years ago ;)

"Array out of bounds" error when trying to add subview in iOS

I'm currently writing an app and I'm experiencing a problem that seems to be caused by code that I did not write (i.e., Apple's classes). I create an instance of a subclass of UIViewController that I wrote. I add it as a child view controller of another custom view controller. Then, when I try to add this new view controller's view as a subview of the parent view controller's view I get a crash with this error.
Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'
I have tested and determined that the problem is specifically cause by trying to add the view as a subview. I reference the view in an NSLog just to make sure that it isn't simply the act of referencing it that's causing the error. I've tried adding the view as a subview of different views and that also crashed, so the problem is not with the parent view. Finally, I have tried to add a different view as a subview to the parent view and that did work, further proving that the parent view is fine, and that the prospective subview is at fault. The code where I allocate it is this:
ScheduleSelectorViewController* selector = [[ScheduleSelectorViewController alloc] initWithNibName:#"ScheduleSelectorViewController" bundle:nil];
This has always worked for me. I don't know what it is I've changed. I don't know enough about the inner workings of subview hierarchy to know which array is empty and is causing this crash, so if anyone can help me out I would be extremely grateful.
If there's any other information I could supply that would help let me know.
UPDATE:
Here is the code where it crashes. I have placed NSLogs to indicate the line at which it breaks.
- (void) addViewControllerToStack:(UIViewController *)controller withKey:(NSString *)key
{
if ( !self.stack ) {
self.stack = [[NSMutableDictionary alloc] init];
}
NSLog(#"subviews %#", [controller.view subviews]);
[[controller view] setFrame:offScreenFrame];
[self addChildViewController:controller];
NSLog(#"code gets to here");
[self.view addSubview:controller.view];
NSLog(#"but not to here");
[self.view bringSubviewToFront:controller.view];
[self.stack setObject:controller forKey:key];
[self.stackKeys addObject:key];
}
For the record, the subviews array is not nil.
Check if you have set view's.hidden = YES; somewhere
I was pulling my hair for more than hour to find out I was hiding my pager control and try to set the pageIndicatorTintColor property later which also throw array out of bounds issue.
Make sure you did not override init/ initWithNibName methods in ScheduleSelectorViewController without calling the super methods.
And of course you can always print out [self.view subviews] for parent view in console to understand if subview array is whether nil. If it is nil you should initiate it before adding any views.

SIGABRT when accessing to just created UIViewController's view

I have the next code:
- (void)func
{
MyViewController *ctrl = [MyViewController new];
[ctrl doSmth];
[self presentViewController:ctrl animated:NO];
}
//------------
- (void)doSmth
{
CGRect *rect = self.view.frame;
// Do something with rect
self.view.frame = rect;
}
Ok, I know, that when -[UIViewController view] is equal to nil then it's being created. And this code did work before my changes (only buttons and labels visibility, nothing extraordinary) and now it throws SIGABRT on self.view, it looks like it cannot be created. Suddenly. If I revert my changes, all work like a magic. And even if I won't call this function it'll crash on presenting and in Summary it'll show that view = 0x00000000.
I've got only one question: WAT?
I've found the error.
After XCode's “refactoring” (renaming some IBOutlets) old outlets had been marked with the ! sign but not removed and nothing XCode told me about it.
What I mean by !-s, is Interface Builder showing not valid outlets with an icon. Not valid outlet means that you have a connection between a view and a property / instance variable that does not exist. So when the NIB will be loaded in runtime, the application will crash, because there are no such property / instance variable.
So if you run in such error, you should either remove the outlet, or add the property / instance variable with the same name to class which you have linked the XIB to (usually a File's Owner).

Crasher in a custom view as UINavigationControllers navigationItem.titleView

I have an UIViewController with several subviews in its view property (UISearchbar and several UIButtons). The UIButtons hooked up to typical IBActions like -(IBAction)buttonPressed:(id)sender for the UIControlEventTouchUpInside state - it doesn't matter if I do it in IB or programmatically.
- (void)viewDidLoad {
MUZTitleViewController *title = [[MUZTitleViewController alloc]
initWithNibName:nil bundle:nil];
self.navigationItem.titleView = title.view;
}
In my project there's also an UINavigationController. When I set the navigationItem.titleView of the UINavigationBar to the view of my UIViewControllers view I get an EXC_BAD_ACCESS exception, as soon as I tap one of the button. I don't know why this is.
I uploaded a small sample project to illustrate my problem: Test010.xcodeproj (it's ARC enabled)
More and more I come to the conclusion that it's not a good idea to use the UIViewControllers view and assign it to the titleView but I don't see any alternative here.
Edit: Sorry, the sample project commented out the call which causes the exception. I reuploaded the linked project file.
Edit^2: As PengOne pointed out I've skipped the exact error message I got:
2011-09-10 23:09:50.621 Test010[78639:f803] -[CALayer buttonPressed:]: unrecognized selector sent to instance 0x9254ae0
2011-09-10 23:09:50.623 Test010[78639:f803] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[CALayer buttonPressed:]: unrecognized selector sent to instance 0x9254ae0'
Have you tried setting NSZombieEnabled to YES? If I do this, the console shows the following output:
2011-09-10 22:56:23.329 Test010[6481:ef03] *** -[MUZTitleViewController
performSelector:withObject:withObject:]: message sent to deallocated
instance 0x7a7ff70
As the project is ARC enabled, the controller seems to get deallocated some time after this line:
MUZTitleViewController *title = [[MUZTitleViewController alloc] initWithNibName:nil bundle:nil];
I am not sure what the best solution is, but a property definitely helps to prevent the exception like so:
// MUZDetailViewController.h
#property (strong, nonatomic) MUZTitleViewController *title;
// MUZDetailViewController.m
#synthesize title;
self.title = [[MUZTitleViewController alloc] initWithNibName:nil bundle:nil];
self.navigationItem.titleView = title.view;
The problem that you were having with ARC can also be resolved by setting the initial view controller of your application as your main window's rootViewController property instead of using addSubview.
Doing this avoids the need to add each custom view controller as a property.

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