I'm trying to understand memory management to do some better apps, but was stopped at one point :
I use some UIButtons. So I alloc them, work with them etc. But i need to release them at one moment.
So I implement deallocmethod for all the object which are usefull all the time the UIViewController is on screen, and which need to be released when it desappeard. So in my UIViewController I implement :
-(void)dealloc
{
NSLog(#"Dealloc call");
[myButton release];
.... //Some objects release
[super dealloc];
}
But i never see the Dealloc call printed, so I think that it doesn't passed by the dealloc method when the UIViewController desappeard.
So, how does it work ? / What is false ?
Thanks !
EDIT : method to change of viewController :
-(void)myMethod
{
if (!nextviewcontroller)
{
nextviewcontroller = [[NextViewController alloc]init];
}
UIView *nextView = nextviewcontroller.view;
UIView *actualView = actualviewcontroller.view;
[actualviewcontroller viewWillAppear:NO];
[nextviewcontroller viewWillDisappear:NO];
[actualView removeFromSuperview];
[self.view addSubview:nextView];
[actualviewcontroller viewDidAppear:NO];
[nextviewcontroller viewDidDisappear:NO];
}
Related
I am trying to draw something in my custom view, but not sure why drawRect could not access its instance data. Here is the steps I tried.
Create a Mac OS X app, with using storyboard checked.
In the storyboard, delete the view, then add a new custom view under the view at the same place. (I tried if the view is not deleted, same).
Assign EEGView class to the newly added custom view.
then run. From the log information, you will notice that the drawRect could not access the instance data although the instance variables get initialized and updated.
In viewCtroller.m
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
myView = [[EEGView alloc] init];
//[self.view addSubview:myView];
//Start Timer in 3 seconds to show the result.
NSTimer* _timerAppStart = [NSTimer scheduledTimerWithTimeInterval:2
target:self
selector:#selector(UpdateEEGData)
userInfo:nil
repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:_timerAppStart forMode:NSDefaultRunLoopMode];
}
- (void)UpdateEEGData
{
// NSLog(#"UpdateEEGData.....1");
// myView.aaa = 200;
// myView.nnn = [NSNumber numberWithInteger:myView.aaa];
// make sure this runs on the main thread
if (![NSThread isMainThread]) {
// NSLog(#"NOT in Main thread!");
[self performSelectorOnMainThread:#selector(updateDisplay) withObject:nil waitUntilDone:TRUE];
}else
{
[self.view setNeedsDisplay:YES];
}
NSLog(#"UpdateEEGData.....2");
[myView setAaa:400];
myView.nnn = [NSNumber numberWithInteger:myView.aaa];
// make sure this runs on the main thread
if (![NSThread isMainThread]) {
// NSLog(#"NOT in Main thread!");
[self performSelectorOnMainThread:#selector(updateDisplay) withObject:nil waitUntilDone:TRUE];
}else
{
[self.view setNeedsDisplay:YES];
}
}
-(void)updateDisplay
{
[self.view setNeedsDisplay:YES];
}
In my custom view class EEGView.m
#implementation EEGView
#synthesize aaa;
#synthesize nnn;
-(id)init{
self = [super init];
if (self) {
aaa = 10;
nnn = [NSNumber numberWithInteger:aaa];
NSLog(#"init aaa: %i", aaa);
NSLog(#"init nnn: %i", [nnn intValue]);
}
return self;
}
- (void)drawRect:(NSRect)dirtyRect {
[super drawRect:dirtyRect];
// Drawing code here.
NSLog(#"drawRect is here");
NSLog(#"drawRect aaa: %i", aaa);
NSLog(#"drawRect nnn: %i", [nnn intValue]);
}
#end
Did I miss anything? Tested in Xcode 7.2 & 7.2. But if I leave the 'using storyboard' unchecked, it works.
Or is it a Xcode bug?
Any advice appreciated.
Thanks in advance.
If you've added EEGView view on storyboard, you shouldn't be also instantiating one in viewDidLoad. You've alloc/init'ed a new one, but it bears no relationship to the one that the storyboard created for you. So, the one created by the storyboard has drawRect called, but you're setting the properties in the separate instance that you created in viewDidLoad which was never added to the view hierarchy (and thus never will have its drawRect called).
When the storyboard instantiates the view controller's view, it will instantiate your EEGView for you. All you need to do is to hook up an IBOutlet for this view in order to get a reference to it from your view controller. (For example, you can control drag from the EEGView in the storyboard scene to the #interface for the view controller that you've pulled up in the assistant editor.)
I want to create a similar class to UIAlertView which doesn't require a strong ivar.
For example, with UIAlertView, I can do the following in one of my UIViewController's methods:
UIAlertView *alertView = [[UIActionSheet alloc] initWithTitle:nil
message:#"Foo"
delegate:nil
cancelButtonTitle:#"Cancel"
otherButtonTitles:nil];
[alertView show];
... and the actionSheet will not be dealloced until it is no longer visible.
If I were to try to do the same thing:
MYAlertView *myAlertView = [[MYAlertView alloc] initWithMessage:#"Foo"];
[myAlertView show];
... the myAlertView instance will automatically be dealloced at the end of the current method I am in (e.g. right after the [myAlertView show] line).
What is the proper way to prevent this from happening without having to declare myView as a strong property on my UIViewController? (I.e. I want myView to be a local variable, not an instance variable, and I would like the MYAlertView instance to be in charge of its own lifecycle rather than my UIViewController controlling its lifecycle.)
Update: MYAlertView inherits from NSObject, so it cannot be added to the Views hierarchy.
UIAlertView creates a UIWindow, which it retains. The alert view then adds itself as a subview of the window, so the window retains the alert view. Thus it creates a retain cycle which keeps both it and its window alive. UIActionSheet works the same way.
If you need your object to stay around, and nothing else will retain it, it's fine for it to retain itself. You need to make sure you have a well-defined way to make it release itself when it's no longer needed. For example, if it's managing a window, then it should release itself when it takes the window off the screen.
If you add it as a subview of another view it will be retained. When the user selects and action or dismisses it, then it should call self removeFromSuperview as it's last act.
I've done my own AlertView with a little trick.
Just retain the object himself and release it on action. With this, you can call your custom alert vies as native one.
#import "BubbleAlertView.h"
#import <QuartzCore/QuartzCore.h>
#interface BubbleAlertView ()
...
#property (nonatomic, strong) BubbleAlertView *alertView;
...
#end
#implementation BubbleAlertView
...
- (id)initWithTitle:(NSString*)title message:(NSString*)message delegate:(id)delegate cancelButtonTitle:(NSString*)cancelButtonTitle okButtonTitle:(NSString*) okButtonTitle
{
self = [super init];
if (self)
{
// Custom initialization
self.alertView = self; // retain myself
//More init stuff
}
return self;
}
...
//SHOW METHOD
- (void)show
{
// We need to add it to the window, which we can get from the delegate
id appDelegate = [[UIApplication sharedApplication] delegate];
UIWindow *window = [appDelegate window];
[window addSubview:self.view];
// Make sure the alert covers the whole window
self.view.frame = window.frame;
self.view.center = window.center;
}
- (IBAction)btPressed:(id)sender
{
//Actions done
[UIView animateWithDuration:0.4f animations:^{
self.vContent.alpha = 0.f;
} completion:^(BOOL finished) {
[self.view removeFromSuperview];
self.alertView = nil; // deallocate myself
}];
}
You need to retain it somehow until it is released.
I do not really understand why you cannot implement it as subclass of UIView. Then you could use the view hierarchy as the keeper of a strong reference (retain +1). But you will have good reasons for not doing so.
If you don't have such a thing then I would use an NSMutableArray as class varialbe (meaning statc). Just declare it in the #interface block and initialize it with nil:
#interface
static NSMutableArray _allMyAlerts = nil;
provide an accessor.
-(NSMutableArray *) allMyAlerts {
if (_allMyAlerts == nil) {
_allMyAlerts = [[NSMutableArray alloc] init];
}
return _allMyAlerts
}
Within the init method do the following:
- (id) init {
self = [super init];
if (self) {
[[self allMyAlerts] addObject:self];
}
}
You will invode some method when the alert is dismissed.
- (void) dismissAlert {
// Do your stuff here an then remove it from the array.
[[self allMyAlerts] removeObject:self];
}
You may want to add some stuff to make it mutli threading save, which it is not. I just want to give an example that explains the concept.
allMyAlert could be an NSMutableSet as well. No need for an array as far as I can see. Adding the object to an array or set will add 1 to the retain count and removing it will reduce it by 1.
I have been struggling with this problem for a while now, so any help would be greatly appreciated.
Here is the situation: My application has a UIViewController subclass called InitialViewController. This view controller has a UIButton, and when that button is pressed it creates a NSObject subclass called MyEngine. Something like this:
#interface InitialViewController : UIViewController <MyEngineDelegate>
...
#end
#implementation InitialViewController
...
-(IBAction)pressedButton:(id)sender {
MyEngine *engine = [[MyEngine alloc] init];
[engine start];
}
Inside start, I present a ViewController (ConflictViewController) modally to get the user's choice:
#interface MyEngine : NSObject <ConflictViewControllerDelegate>
...
-(void) start;
#end
#implementation MyEngine
...
-(void) start {
ConflictViewcontroller *cvc = [[ConflictViewController alloc] initWithNibName:#"ConflictViewController" bundle:nil];
cvc.modalPresentationStyle = UIModalPresentationFormSheet;
cvc.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
cvc.delegate = self;
UIWindow *window = [(MyAppDelegate *) [[UIApplication sharedApplication] delegate] window];
[[window rootViewController] presentModalViewController:cvc animated:YES];
}
#end
ConflictViewController is really simple. It just waits for the user to decide, and when the user press the button, it send the message to the delegate, and dismiss itself.
-(IBAction)didSelectConflict:(id)sender {
UISegmentedControl *seg = (UISegmentedControl*) sender;
[self.delegate didResolveConflictChoice:seg.selectedSegmentIndex];
[self dismissModalViewControllerAnimated:YES];
}
I've checked every connection, all the delegates are working properly.
What is going wrong is:
When MyEngine receives the user's choice in it's implementation of didSelectConflict: it cannot continue properly because all of it's properties have gone null.
When the MyEngine presents the ConflictViewController, the program continues the execution and when start finishes, it goes back to pressedButton: and when this method is closed, the MyEngine object gets released.
What i want to know is if there is way around this ? Has anyone done something like this in another way ?
The question here is: How to get the user's choice properly when the choice is too complex to use UIAlertView.
Sorry for the long question, I simplified it as much as I could. Thanks for your time, any links, comments, or any kind of help is greatly appreciated
Why are you initializing MyEngine *engine in the IBAction, if you wish to use a MyEngine object why don't you make a global declaration in your InitialViewController and just call [engine start] in the IBaction. Then when the delegate method returns the selected index you can apply that to a global int in your initial view controller and continue on your way. Hope that makes sense
Make your method start as
-(void) startWithDelegate:(id)del {
ConflictViewcontroller *cvc = [[ConflictViewController alloc] initWithNibName:#"ConflictViewController" bundle:nil];
cvc.modalPresentationStyle = UIModalPresentationFormSheet;
cvc.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
cvc.delegate = del;
UIWindow *window = [(MyAppDelegate *) [[UIApplication sharedApplication] delegate] window];
[[window rootViewController] presentModalViewController:cvc animated:YES];
}
and
-(IBAction)pressedButton:(id)sender {
MyEngine *engine = [[MyEngine alloc] init];
[engine startWithDelegate:self];
}
implement didResolveConflictChoice: in InitialViewController and get the delegate call there.
OR you can use UIActionSheet if suitable.
I have a button with IBAction, which shows another window:
-(IBAction)someButtonClick:(id)sender
{
anotherView = [[NSWindowController alloc] initWithWindowNibName:#"AnotherWindow"];
[anotherView showWindow:self];
}
I worry about memory management in here. I allocate an object in this IBAction and don't released it. But how can i do it? If i released this object after showing, window will closing immediately.
The view is stored in an instance variable and you have access to it anywhere in your class. Release it in the code that dismisses the view.
Since anotherView is an instance variable you can release it in your dealloc method. But then you still have a memory leak, since every time your button is clicked a new instance of the window controller is created, but only the last one can be freed. You really should use accessors for this. Here is my suggestion:
- (NSWindowController *) anotherView;
{
if (nil == anotherView) {
anotherView = [[NSWindowController alloc] initWithWindowNibName:#"AnotherWindow"];
}
return anotherView;
}
- (void) setAnotherView: (NSWindowController *) newAnotherView;
{
if (newAnotherView != anotherView) {
[anotherView release];
anotherView = [newAnotherView retain];
}
}
- (void) dealloc;
{
[self setAnotherView: nil];
[super dealloc];
}
- (IBAction) someButtonClick: (id) sender;
{
[[self anotherView] showWindow: self];
}
If you use a Objective-C 2.0 property you don't have to write the setter.
And also you should rename your instance variable, the name should reflect what it is. And a View is not a Window Controller.
I have a UIView which I create programmatically roughly like so:
#implementation SlideShowView
- (id)initWithImages
{
…
if (self=[super initWithFrame:CGRectMake(0, 0, 320, 480)])
{
// init objects here
}
return self;
}
- (void)dealloc
{
printf("dealloc slide show view\n");
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"unlockUI" object:nil ];
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"setUserRating" object:nil ];
[mCurrentImageView release];
[mRightImageView release];
[mLeftImageView release];
[mImages release];
[queue cancelAllOperations];
[queue release];
[managingArray release];
[super dealloc];
}
with a uiview controller that contains this:
- (void)loadView {
{
...
self.view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
self.slideShowViewObject = [[SlideShowView alloc] initWithImages];
[self.view addSubview:slideShowViewObject];
…
}
-(void)dealloc
{
[slideShowViewObject release];
[self.slideShowViewObject removeFromSuperview];
printf("dealloc of slideshow view controller\n");
[super dealloc];
}
this seems to be able to dealloc both the view controller and view but when I push this view controller back onto the stack I get the message with zombie enabled: -[SlideShowView retain]: message sent to deallocated instance 0x43ab160
should the alloc not be creating a new instance of the view when the controller is pushed? I don't understand and after spending many hours reading through other posts as well as looking at memory guides I would say I'm thoroughly stumped! Can someone offer any pointers? I only posted the code I deemed necessary but I can post more if need be.
Thanks so much!
First, you shouldn't call both [super init] and [super initWithFrame:], only one of the two in your UIView subclass.
Secondly, you should only set self.view in a view controller in the -loadView method, which is designed for you to create your views. Normally, unless you need to do certain types of setup such as initializing variables, etc, you shouldn't need to override -init in UIViewController subclasses.
finally, after finagling with the code again tonight I finally got it working. The key piece I was not releasing appears to be
[self.view release];
I suppose this makes perfect sense since I was adding the view as a subview of this alloc'd self view, but I had tried this before. Perhaps cleaning up the code is what made it work this time.