Why is my loaded nib crashing when memory is released? - iphone

Question

If I run Build and Analyze this loads without errors according to the Analyzer but the app crashes. If I remove the [myStates release]; analyzer complains about possible leak but the nib loads and runs just fine. MyStateList is a nib which has a pickerview inside that loads a plist if this helps. Please help.
Main TrialViewControllerViewController Implementation File
#import "TrialViewControllerViewController.h"
#import "MyStateList.h"
#implementation TrialViewControllerViewController
- (void)viewDidLoad {
[super viewDidLoad];
MyStateList *myStates = [[MyStateList alloc] initWithNibName:#"MyStateList" bundle:nil];
[self.view addSubview:[myStates view]];
//[myStates release];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
- (void)viewDidUnload {
}
- (void)dealloc {
[super dealloc];
}
#end
Here is what i am trying to load
MyStateList.h
#import <UIKit/UIKit.h>
#interface MyStateList : UIViewController <UIPickerViewDelegate, UIPickerViewDataSource> {
UIPickerView *pickerView;
NSMutableArray *statesArray; // Written array
NSDictionary *stateListDictionary,*stateListDictionaries;
NSArray *firstDisplayArray,*updateDisplayArray,*switchDisplayArray;
NSInteger dTag;
NSString *nott,*verify,*notes;
IBOutlet UILabel *labelOne,*labelTwo,*labelThree,*labelName;
}
#property (nonatomic, retain) UIPickerView *pickerView;
#property (nonatomic, retain) NSDictionary *stateListDictionary,*stateListDictionaries;
#property (nonatomic, retain) NSArray *firstDisplayArray,*updateDisplayArray,*switchDisplayArray;
#property (nonatomic, retain) IBOutlet UILabel *labelOne,*labelTwo,*labelThree,*labelName;
#property (nonatomic, retain) NSString *nott,*verify,*notes;
- (void)loadData;
- (void)placeData;
- (void)createPicker;
#end
MyStateList.m
#import "MyStateList.h"
#implementation MyStateList
#synthesize pickerView;
#synthesize stateListDictionary,stateListDictionaries,firstDisplayArray,updateDisplayArray,switchDisplayArray ;
#synthesize labelOne,labelTwo,labelThree,labelName;
#synthesize nott,verify,notes;
- (void)viewDidLoad
{
[super viewDidLoad];
[self createPicker];
}
-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{
return 1;
}
-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
return [statesArray count];
}
-(UIView *)pickerView:(UIPickerView *)pickerViewCust viewForRow:(NSInteger)row forComponent: (NSInteger)component reusingView:(UIView *)view
{
NSString *rowItem = [statesArray objectAtIndex: row];
UILabel *lblRow = [[[UILabel alloc] initWithFrame:CGRectMake(0.0f, 0.0f, [pickerViewCust bounds].size.width, 44.0f)]autorelease];
[lblRow setTextAlignment:UITextAlignmentCenter];
[lblRow setTextColor: [UIColor blueColor]];
[lblRow setText:rowItem];
[lblRow setBackgroundColor:[UIColor clearColor]];
return lblRow;
}
- (void)createPicker
{
NSString *path = [[NSBundle mainBundle] pathForResource:
#"StateArray" ofType:#"plist"];
stateListDictionary = [NSDictionary dictionaryWithContentsOfFile:path];
labelName.text = [NSString stringWithFormat:#"Arizona"];
[self loadData];
float screenWidth = [UIScreen mainScreen].bounds.size.width;
float pickerWidth = screenWidth * 1 / 2;
float xPoint = screenWidth / 2 - pickerWidth / 1;
pickerView = [[UIPickerView alloc] init];
[pickerView setDataSource: self];
[pickerView setDelegate: self];
[pickerView setFrame: CGRectMake(xPoint, 280.0f, pickerWidth, 180.0f)];
pickerView.showsSelectionIndicator = YES;
[pickerView selectRow:2 inComponent:0 animated:YES];
[self.view addSubview: pickerView];
}
- (void)loadData
{
firstDisplayArray = [stateListDictionary objectForKey:#"Arizona"];
dTag = 1;
[self placeData];
stateListDictionary = nil; // kill the list
statesArray = [[NSMutableArray alloc] init];
[statesArray addObject:#"Alabama"];
[statesArray addObject:#"Alaska"];
[statesArray addObject:#"Arizona"];
[statesArray addObject:#"Arkansas"];
[statesArray addObject:#"California"];
}
- (void)placeData
{
if (dTag == 1)
{
switchDisplayArray = firstDisplayArray;
dTag = 0;
} else {
switchDisplayArray = updateDisplayArray;
}
nott = [switchDisplayArray objectAtIndex:0];
verify = [switchDisplayArray objectAtIndex:1];
notes = [switchDisplayArray objectAtIndex:2];
labelOne.text = nott;
labelTwo.text = verify;
labelThree.text = notes;
}
- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent: (NSInteger)component
{
NSString *path = [[NSBundle mainBundle] pathForResource:
#"StateArray" ofType:#"plist"];
stateListDictionaries = [NSDictionary dictionaryWithContentsOfFile:path];
labelName.text = [statesArray objectAtIndex: row];
updateDisplayArray = [stateListDictionaries objectForKey:labelName.text];
[self placeData];
}
- (void)dealloc
{
[pickerView release];
[stateListDictionary release];
[stateListDictionaries release];
[statesArray release];
[super dealloc];
}
#end

Answer 1

If I had to guess, MyStatesList is a subclass of UIViewController.
If you release myStates at the end of the block, you're essentially removing the brain from your view controller, but leaving its body there. You need to keep the controller itself around as well as the view, as the view is owned by the controller. Not the other way around.
The view from your view controller is retained by the view, but you killed the view controller itself. The bigger problem is you CAN'T just add views from UIViewControllers in this manner. On iOS5 you have the ability to use addChildViewController: and prior to that you can use one of the provided container controllers.

Answer 2

You do indeed need to release your MyStateList object.
Here's what's happening:
You initialize a new MyStateList, which has a retain count of 1
You add a subview to your view, and that subview is NOT the MyStateList object, but the ivar view of your MyStateList object.
When you don't release your myStates object, you are indeed leaking this object, since nothing has a reference to this object anymore, and the memory was never deallocated. (Its retain count never reached 0.)
That having been said, what kind of error occurs when your application crashes? I'm guessing that MyStateList is a UIViewController, and the view is then attempting to access/communicate with its parent, which has been released/deallocated.

Answer 3

In your -(void)dealloc; you are calling [super dealloc] first, this is wrong. Make it the last call in the method. This should fix your crash.
- (void)dealloc
{
// Wrong Way
[super dealloc];
[pickerView release];
[stateListDictionary release];
[stateListDictionaries release];
[statesArray release];
}
`
- (void)dealloc
{
// Right way
[pickerView release];
[stateListDictionary release];
[stateListDictionaries release];
[statesArray release];
[super dealloc];
}

Answer 4

you add the view [myStates view], to the controller's view, so the view is hold by the controller's view.
then you release "myStates" for avoid memeory leak, it is removed.
and I guess in your view [myStates view], there must be some delegates related to the object "myState", but it was removed just before. So, the app crash.
To avoid both problems, memory leak and crash. I think you should make the "myStates" hold by your controller as a member variable. And you could release "myState" when your viewUnloaded.