I am trying to make a simple iphone app and I have been playing around with features and recently, delegates. I am just confused with regards to memory management because apparently "good code" makes my app crash with exc_bad_access.
I have an object with two data members and implementation empty for now.
#implementation semester: NSObject{
NSInteger ID;
NSString *name;
}
then my delegate method:
- (void) receiveSemester:(semester *)newSemester {
[test setText:newSemester.name];
}
and a view that is used as a form which has:
#interface addSemesterController : UIViewController {
id<ModalViewDelegate> delegate;
UITextField *txtName;
UILabel *prompt;
UIButton *ok;
UIButton *cancel;
}
all objects are made properties and synthesized in the application file. Here is the method that used the delegate:
- (IBAction) okClick:(id)sender{
// create semester object and return it
semester *created = [[semester alloc] init];
created.name = txtName.text;
[delegate receiveSemester:created];
[self dismissModalViewControllerAnimated:YES];
}
And my dealloc method looks like this:
- (void)dealloc {
/*
[txtName dealloc];
[prompt dealloc];
[ok dealloc];
[cancel dealloc];
*/
[super dealloc];
}
With the deallocs of the objects contained in the form commented out, my app runs ok. However, when I uncomment them, I receive the exc_bad_access error in my delegate protocol:
// in main view controller
- (void) receiveSemester:(semester *)newSemester {
[test setText:newSemester.name];
// test is a UILabel
}
I tried the zombie method and it says that the label calls a released object. I am not releasing my semester object in the "form" controller, and even if I was the delegate function is called before deallocating the view.
Clearly I should not be releasing the objects in the dealloc method, I am just unclear in the why I shouldn't.
Again, thanks in advance for the help.
Use release to release the variables instead of calling dealloc on variables, due to this you are having issue -
- (void)dealloc {
[txtName release];
[prompt release];
[ok release];
[cancel release];
[super dealloc];
}
try writing
[txtName release];
[prompt release];
[ok release];
[cancel release];
instead of dealloc and these objects will be deallocated properly
Related
I know the ARC in iOS 5 but I'm now developing pre-iOS 5 code style, and want to solve this problem by a manual release approach.
My only goal for this is to make a very handy custom alert view with UITextField.
I have a 'BigView' view that has many functions in it. And it can possibly generate many UIAlertView for many different situation on the display with that view. So I know the way use UIAlertViewDelegate for each alert view, but kind of experimentally try want to make this as like UIButton's 'addTarget'(actually it's UIControl's method).
Briefly,
This is in the part of 'BigView' class and my 'TextAlert' instance fired by a button for email gathering .
BigView.m
- (void)emailFeedback:(id)sender
{
TextAlert *textAlert = [[TextAlert alloc] initWithTitle:#"Enter your email address"];
[textAlert setTarget:self action:#selector(textAlertInputed:)];
// [textAlert release];
}
- (void)textAlertInputed:(NSString *)text
{
NSLog(#"text alert inputed, text: %#", text);
}
and these are full my TextAlert files.
TextAlert.h
#import <Foundation/Foundation.h>
#interface TextAlert : NSObject <UIAlertViewDelegate>
{
UIAlertView *alertView;
UITextField *textField;
id target;
SEL action;
}
- (id)initWithTitle:(NSString *)title;
- (void)setTarget:(id)target action:(SEL)action;
#end
TextAlert.m
#import "TextAlert.h"
#implementation TextAlert
- (id)initWithTitle:(NSString *)title
{
if (self = [super init])
{
alertView = [[UIAlertView alloc] initWithTitle:title message:#"beneath" delegate:self cancelButtonTitle:#"Cancel" otherButtonTitles:#"OK", nil];
textField = [[UITextField alloc] initWithFrame:CGRectMake(12, 45, 260, 25)];
CGAffineTransform myTransform = CGAffineTransformMakeTranslation(0, 60);
[alertView setTransform:myTransform];
[textField setBackgroundColor:[UIColor whiteColor]];
[alertView addSubview:textField];
[alertView show];
}
return self;
}
- (void)dealloc
{
[alertView release]; alertView = nil;
[textField release]; textField = nil;
[super dealloc];
}
- (void)setTarget:(id)_target action:(SEL)_action
{
target = _target;
action = _action;
}
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
[target performSelector:action withObject:textField.text];
}
#end
So my main problem is the releasing point of TextAlert instance in the 'BigView' as you can see the only comment part full codes above. Of course if I remove that comment out, I got crash for call for method of deallocated.
And I also get error make textAlert instance as autoreleased one.
For me, the only solution for this is to make the 'textAlert' object in the 'BigView' a member of 'BigView' not local object. But in that case, my initial goal for handy and lightweight approach for this is not satisfied, I think. And the 'BigView' has already many member instances so I don't want to add any more.
So any suggestions? Or It will be welcome any comment for this trying. I'm ready to hear any
reproves to my insufficient code, really.
Thanks in advance,
MK
If everything works except your release problem you should only consider implementing public "show" method and private "dismiss" method (in your custom alert view).. In show method you should call [self retain] beside other things and on dismiss (add this target to button or whatever dismisses your view) call [self relese].
This isn't directly what you asked for, but could help you anyway.
Handling multiple UIAlertViews in a single UIViewController can be painful. When I ran into this problem, I found an alternative control on github, called BlockAlertsAndActionSheets. It uses blocks instead of delegates, the appearance can be fully customized (even to the default Apple-style) and there is also an "AlertView with an UITextField". Works good for me and I didn't have to reinvent that wheel! ;-)
A problem happens when I was trying to release one of my instance variables and reassign it a new value.
I would like to release the address that a instance variable points to, and re-assign a new value to it.
The code look like this:
The .h
#interface MapPageController : UIViewController<MKMapViewDelegate> {
AddressAnnotationManager *addAnnotation;
}
- (IBAction) showAddress;
#property (nonatomic, retain) AddressAnnotationManager *addAnnotation;
The .m
#synthesize addAnnotation;
- (IBAction) showAddress {
if(addAnnotation != nil) {
[mapView removeAnnotation:addAnnotation];
[addAnnotation release]; // this generates the problem
addAnnotation = nil;
}
addAnnotation = [[AddressAnnotationManager alloc] initWithCoordinate:location];
addAnnotation.pinType = userAddressInput;
addAnnotation.mSubTitle = addressField.text;
}
However, with [addAnnotation release], a EXC_BAD_ACCESS always comes along if the process runs through it.
Thus I printed out the memory address in the dealloc of AddressAnnotationManager:
- (void)dealloc {
NSLog(#"delloc Instance: %p", self);
[super dealloc];
}
I turned on Zombie, the console gave me something like this:
2010-10-10 17:02:35.648 [1908:207] delloc Instance: 0x46c7360
2010-10-10 17:02:54.396 [1908:207] -[AddressAnnotationManager release]: message sent to deallocated instance 0x46c7360*
It means the code reaches dealloc before the problem occurs.
I have checked all the possible places where I could release addAnnotation. However, I could not find any.
Does anyone happen to find what the problem is?
I suspect that this is not the whole code involving the addAnnotation variable. Most likely [mapView removeAnnotation:addAnnotation];, which releases addAnnotation, already makes the reference count drop to zero. Do you have something like this in your code somewhere ?
[mapView addAnnotation:addAnnotation];
[addAnnotation release];
If so, then you have transfered the complete ownership of addAnnotation to the mapView and you don't need to release it in showAddress any more, which means that removeAnnotation: is enough.
Using the PhotoScroller example from Apple, to reuse the memory allocated for views, I cannot get the memory released once the retain count hits 0. Here my code for a better understanding:
This piece is an extract from PhotoScroller
PhotoViewController.m
- (void)configurePage:(ImageScrollView *)page forIndex:(NSUInteger)index
{
page.index = index;
page.frame = [self frameForPageAtIndex:index];
[page displayPage:index];
}
ImageScrollView.h
#interface ImageScrollView : UIView
{
UIViewController *vc;
NSUInteger index;
}
#property (assign) NSUInteger index;
- (void)displayPage:(int)indice;
#end
ImageScrollView.m
- (void)dealloc
{
[vc release];
[super dealloc];
}
- (void)displayPage:(int)indice
{
//remove previous view
[vc.view removeFromSuperview];
[vc release];
vc = nil;
//NSLog(#"vc retain %i", [vc retainCount]);
// make a new viewController for the new page
Class clss = NSClassFromString([NSString stringWithFormat:#"page_0%i", indice + 1]);
vc = [[clss alloc] initWithNibName:[NSString stringWithFormat:#"page_0%i", indice + 1] bundle:nil];
[self addSubview:vc.view];
}
The classes "page_0x" are UIViewControllers. So far have nothing but a UIImageView on the XIB.
An example of page_01:
#implementation page_01
-(BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
// Overriden to allow any orientation.
return YES;
}
- (void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
- (void)viewDidUnload {
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (void)dealloc {
[super dealloc];
}
#end
Memory peaks to 148 MB on device. Gives me a memory warning Level 1, then releases some memory. Goes down to 95 MB. Keeps going up and down.
Perhaps your page_0x view controllers are getting freed, but something they've created isn't. Some things to check:
Set a breakpoint in the dealloc method of your page_0x view controllers. Is it getting called?
Check all the IBOutlets and other instance variables of your page_0x view controllers. Are they all being released properly in their class's dealloc method?
Run Build & Analyze. Does it turn up anything?
Try running the Leaks Instrument. It can tell you what kind of objects are actually leaking.
(EDIT) Grasping at straws now. You don't have NSZombieEnabled turned on, do you?
(EDIT 2) You say you're throwing a .png on it. What happens if you remove that .png?
If you're running in the simulator, try it on the device. (See this question.)
I am having a uiviewcontroller instance and when I am releasing it the dealloc method of it is called.
I have released some objects in dealloc method of that uiviewcontroller.
If I comment [super dealloc] the app is working fine but if don't it is crashing.
I think there is no problem with the releases that I am doing in that method, but if I do [super dealloc] it is crashing.
Can any one help me out with this?
Hard to tell from your post without more information, but does your dealloc method look like this?
- (void)dealloc {
[super dealloc];
self.someProperty = nil;
}
Because if it does, you're calling a setter method on a deallocated instance. You should always call [super dealloc] last:
- (void)dealloc {
self.someProperty = nil;
[super dealloc];
}
Not sure if that helps. Try posting what your dealloc method looks like if not. Hard to troubleshoot in the dark.
It's not possible to help you without more information. The code you described is perfectly fine. The problem is in some other part of your app.
You probably access the view controller after releasing it, so the problem is not the [super dealloc] but any other place in you application that accesses the view controller.
Maybe you are releasing the controller in the wrong place. That could be why your [super dealloc] in your ViewController.m is crashing
You shouldn't called [viewController release] until you want that controller to die. For example, if you have an application with just a viewcontroller you must not release it until the application ends. This is because that controller needs to stay alive all the time to control the view. If you have in your ApplicationDelegate something like this, it will crash:
- (void)applicationDidFinishLaunching:(UIApplication *)application {
UIViewController *controller = [[UIViewController alloc] init];
[window addSubview:controller.view];
[controller release]; //this will crash
}
Instead of that you should place your viewcontroller in the header file (.h) and release it in the dealloc method:
- (void)dealloc {
[controller release];
[window release];
[super dealloc];
}
I hope this helps.
I want to organize somehow my iPhone game's level-views, but I simply cannot (without expanding Object Allocations). I made a really "skeleton" of my code (this game has 2 levels, the goal is to release the iPhone display). I just cannot dealloc the previous level, so Instrunments shows incrementing BGTangramLevel instances.
Please, take a look on it, I need some helpful ideas on designing (my 3rd question on it).
viewcontroller.h
#interface compactTangramViewController : UIViewController
{
//The level.
BGTangramLevel *currentLevel;
UIColor *levelColor;
}
//It is to be just a reference, therefore I use assign here.
#property (nonatomic, retain) BGTangramLevel *currentLevel;
-(void) notificationHandler: (NSNotification*) notification;
-(void) finishedCurrentLevel;
#end
viewcontroller.m
#implementation compactTangramViewController
#synthesize currentLevel;
//Initializer functions, setting up view hierarchy.
-(void) viewDidLoad
{
//Set up levelstepper.
levelColor = [UIColor greenColor];
//Set up "state" classes.
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(notificationHandler:) name:#"finishedCurrentLevel" object:nil];
//Attach level 1.
currentLevel = [BGTangramLevel levelWithColor: levelColor frame:self.view.frame];
[self.view addSubview:currentLevel];
[super viewDidLoad];
}
//Release objects.
-(void) dealloc
{
[currentLevel release];
[super dealloc];
}
//Notification handling.
-(void) notificationHandler: (NSNotification*) notification
{
//Execute level swap.
if ([notification name] == #"finishedCurrentLevel") [self finishedCurrentLevel];
}
-(void) finishedCurrentLevel
{
//Remove previous level.
[currentLevel removeFromSuperview];
//[currentLevel release];
//Step level.
if (levelColor == [UIColor greenColor]) levelColor = [UIColor blueColor]; else levelColor = [UIColor greenColor];
//Attach level 2.
currentLevel = [BGTangramLevel levelWithColor: levelColor frame:self.view.frame];
[self.view addSubview:currentLevel];
}
#end
BGTangramLevel.h
#interface BGTangramLevel : UIView
{
BOOL puzzleCompleted;
}
//Initializer.
+(BGTangramLevel*)levelWithColor: (UIColor*) color frame: (CGRect) frame;
//Test if the puzzle is completed.
-(void) isSolved;
#end
BGTangramLevel.m
#implementation BGTangramLevel
//Allocated instance.
+(BGTangramLevel*)levelWithColor: (UIColor*) color frame: (CGRect) frame
{
BGTangramLevel *allocatedLevel = [[BGTangramLevel alloc] initWithFrame:frame];
allocatedLevel.backgroundColor = color;
return allocatedLevel;
}
//Finger released.
-(void) touchesEnded: (NSSet*)touches withEvent: (UIEvent*)event
{
//The completement condition is a simple released tap for now...
puzzleCompleted = YES;
[self isSolved];
}
//Test if the puzzle is completed.
-(void) isSolved
{
//"Notify" viewController if puzzle has solved.
if (puzzleCompleted) [[NSNotificationCenter defaultCenter] postNotificationName:#"finishedCurrentLevel" object:nil];
}
-(void) dealloc
{
NSLog(#"Will ever level dealloc invoked."); //It is not.
[super dealloc];
}
#end
So what should I do? I tried to mark autorelease the returning level instance, release currentLevel after removeFromSuperview, tried currentLevel property synthesized in (nonatomic, assign) way, but Object Allocations still grow. May I avoid Notifications? I'm stuck.
You need to follow retain/release rules more closely. You definitely should not experimentally add retain and release and autorelease in places just to find something that works. There's plenty written about Cocoa memory management already, I won't repeat it here.
Specifically, BGTangramLevel's levelWithColor:frame: method should be calling [allocatedLevel autorelease] before returning allocatedLevel to its caller. It doesn't own the object, it's up to the caller to retain it.
You also need to know the difference between accessing an instance variable and accessing a property. Cocoa's properties are just syntactic-sugar for getter and setter methods. When you reference currentLevel in your view controller you are dealing with the instance variable directly. When you reference self.currentLevel you are dealing with the property.
Even though you've declared a property, currentLevel = [BGTangram ...] simply copies a reference into the variable. In viewDidLoad, you need to use self.currentLevel = [BGTangram ...] if you want to go through the property's setter method, which will retain the object (because you declared the property that way). See the difference?
I think your leak is happening in finishedCurrentLevel. If you had used self.currentLevel = [BGTangram ...], the property's setter method would be called, which would release the old object and retain the new one. Because you assign to the instance variable directly, you simply overwrite the reference to the old level without releasing it.
Calling [currentLevel release] in the dealloc method of your view controller is correct.