I'm sorry for repost. What have really bug me is if property retain should release when:
case 1 : (code below) button is already alloc in init: then add to subview then release it, and by any chance I set the button property in another class (I didn't release in dealloc:) it will leak then?
case 2 : button is already alloc in init: then add to subview then release it, and by any chance I didn't set the any button property in another class (I didn't use the property) (I release it in dealloc) then it will crash.
So what should I do if I want to alloc button in init: and I want to set the property too ?
#interface SomeClass : UIView {
UIButton *_button;
}
#property (nonatomic, retain)UIButton *button;
#implementation SomeClass
#synthesize button = _button;
- (id)init {
_button = [[UIbutton alloc] initWithFrame:CGRectMake(0.0f,0.0f,100.0f,20.0f)];
[[_button titleLabel] setFont:BUTTON_FONT];
[_button setBackgroundImage:[[UIImage imageNamed:#"button_blue.png"] stretchableImageWithLeftCapWidth:20.0f topCapHeight:15.0f] forState:UIControlStateNormal];
[_button setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
[_button setTitleShadowColor:[UIColor blackColor] forState:UIControlStateNormal];
[[_button titleLabel] setShadowOffset:CGSizeMake(0.0f, 1.0f)];
[_button addTarget:self action:#selector(buttonDidTapped:) forControlEvents:UIControlEventTouchUpInside];
[self addSubView:_button];
[_button release];
}
- (void)dealloc {
//[self.button release]; // case 1
[self.button release]; // case 2
[super dealloc];
}
#end
So what should I do if I want to alloc button in init: and I want to set the property too ?
Here's how your code should look:
#implementation SomeClass
#synthesize button = _button;
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
UIButton *button = [[UIbutton alloc] initWithFrame:CGRectMake(0.0f,0.0f,100.0f,20.0f)];
// Setup the button here...
[self addSubView:button];
self.button = button;
[button release];
}
return self;
}
- (void)dealloc {
[_button release];
[super dealloc];
}
#end
Changes I made:
initWithFrame: is the designated initializer of the UIView, so that's the init method you've got to override
Always check to make sure that your superclass initialized successfully before you setup your class
You've got to return self at the end of your init statements. I don't think your code would have compiled as written.
You created a property, you should use it. Use a temp variable to do all the setup for your button, then when you're finished with setup, use the property accesssor to set the variable and release your temp variable.
Because you only use the property to get/set your button, when it's time to dealloc you can guarantee that the _button iVar will either be valid or nil. Either way calling release on that variable is OK.
I don’t understand what you mean by “using it for read-only”. As declared, the property is read-write both for the class itself and from the outside. But the question can be reasonably answered nevertheless – once your class retains some object, it must release it when it gets deallocated.
P.S. I think you can safely drop the underscore prefix for private variables, it serves no real purpose and makes you write more code. In fact, with modern runtimes you can even drop the instance variable declaration:
#interface Foo : NSObject {}
#property(assign) BOOL bar;
#end
#implementation Foo
#synthesize bar;
#end
OK, third attempt: The problem is that you are in fact setting the property by assigning to the instance variable. Properties and instance variables are closely tied, when you give the following declaration…
#synthesize button = _button;
…you are saying that the _button instance variable should be used to store the value of the button property. Which means that your code over-releases, since you alloc the button in init (+1), release the button in init (-1) and then release again in dealloc (-1 again).
If you have not yet studied the Cocoa Memory Management Guide, do it. Even if you don’t plan to read any other documentation (which would be a pity), make an exception with this one, it will pay you back plenty.
sure, You should release it, because you have used retain for it.
In your -init method, you have a balanced retain/release call. So you don't need to release it again. But by doing it, you are sacrificing the reliability of the value held by _button. If somewhere down the lane the button is removed from the subviews, the button's retainCount could hit zero and it can be deallocated. Then the value held by _button is garbage. So you should not release _button in -init and rather you should do that in -dealloc.
Now, if you access the property elsewhere (outside this UIView object), you don't need to release it again unless you retain it there.
Try to replace [self.button release]; with [self.button removeFromSuperview];
Related
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];
}
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 a int that resets itself every time the view re-opens/leaves. I have tried every way of declaring the int that i can think of, from public, to instance variable to global variable, but it still seems to reset!
#interface MainGameDisplay : UIViewController
extern int theDay;
#implementation MainGameDisplay
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(#"%i", theDay);
}
- (IBAction)returnToHome:(id)sender {
ViewController *new = [[ViewController alloc] initWithNibName:nil bundle:nil];
[self presentViewController: new animated:YES completion:NULL];
NSLog(#"%i", theDay);
}
- (IBAction)theDayAdder:(id)sender {
theDay++;
}
Okay so theDay is a global integer variable. on View load NSLog returns an output of 0. I can then click theDayAdder as many times as I want, and when I click returnToHome, it will tell me what theDay is. When I come back to MainGameDisplay page however, theDay will be reset back to zero, even though it is a global variable?
Output:
0
N (number of times you clicked 'theDayAdder' button)
0
The problem is that you alloc init'ing a new instance of MainGameDisplay every time you go back to it, so of course your global variable will be reset to 0. You need to create a property (typed strong) in ViewController, use that to go back to the same instance each time.
- (IBAction)returnToGameDisplay:(id)sender {
if (! self.mgd) {
self.mgd = [[MainGameDisplay alloc] initWithNibName:nil bundle:nil];
}
[self presentViewController: self.mgd animated:YES completion:NULL];
NSLog(#"%i", theDay);
}
In this example mgd is the property name created in the .h file.
You should know that viewDidLoad() is called when the view is loaded--not when when the view "opens" as you say. You might have a view opened in a retained value and re-opened time and time again and have vieDidLoad() called only once. However, whenever the view becomes visible, then viewWillAppear() is the delegate that is called. So, try outputting your value in viewWillAppear()--instead of viewDidLoad() and call the view appropriately (i.e., have it stick around and not created every time you need it). This will keep the view from being destroyed between calls. The code for your view should look like the following:
#interface MainGameDisplay : UIViewController
extern int theDay;
#implementation MainGameDisplay
- (void)viewDidLoad {
[super viewDidLoad];
}
-(void) viewWillAppear:(BOOL) animated {
[super viewWillAppear:animated];
NSLog(#"%i", theDay);
}
- (IBAction)returnToHome:(id)sender {
ViewController *new = [[ViewController alloc] initWithNibName:nil bundle:nil];
[self presentViewController: new animated:YES completion:NULL];
NSLog(#"%i", theDay);
}
- (IBAction)theDayAdder:(id)sender {
theDay++;
}
The parent of the view (I assume the appDelegate) should do the following
#property (nonatomic, strong) MainGameDisplay *mainGameDisplay = [[MainGameDisplay alloc] initWithNib:#"MainGameDisplay" …]
ViewDidLoad() is called once--after the view is created and loaded. However, viewWillAppear() and other functions triggered by IBAction etc. are called appropriately.
extern variables are meant to be constant. If you expect your MainGameDisplay class to be long-lived, or if theDay is otherwise only supposed to be tied to that class, why not either declare theDay as a property, or, if you only ever need to set it internally in MainGameDisplay, as an ivar.
The other alternative, if you want that value to continue to exist independently of the class instance where it's declared, is to declare it static. A static var will retain its value, even across the lifetime of different instances of the class where it's declared.
When I use a UIPopoverController and give it a contentViewController, I cannot seem to get the contentViewController to correctly be deallocated (as evidenced by the fact that the contentViewController.viewDidUnload is never getting called).
Code to create and display the popup:
PopupTestViewController *popupTest = [[PopupTestViewController alloc] initWithNibName:#"PopupTestViewController" bundle:nil];
popupTest.mainViewController = self;
self.popoverController = [[UIPopoverController alloc] initWithContentViewController:popupTest];
self.popoverController.popoverContentSize = popupTest.view.frame.size;
self.popoverController.delegate = self;
[self.popoverController presentPopoverFromRect:button.frame inView:button.superview permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];
Now I am assuming that the contentViewController (in the code above, this is PopoverTestViewController) should be deallocated when the UIPopoverController is closed (whether by clicking off of it, or be explicitly dismissing it). But viewDidUnload is never called. I did notice, however, that if I define a dealloc method for PopoverTestViewController, that is called appropriately.
So my question is: why is viewDidUnload never getting called?
(And I'm using ARC).
viewDidUnload is not guaranteed to get called. It only gets called when the application receives a memory warning and the receiving ViewController has view loaded but is off screen.
When the view is loaded and retain count reaches zero, viewDidUnload is not called.
You can find more details in the documentation.
Instructions on when to release what objects can be found in the same document.
This is a little different than I've used UIPopoverController. Since you manually alloc'ed popupTest, you definitely need to manually release it. The UIPopoverController instance will retain popupTest when initWithContentViewController: is called.
Furthermore, if you are defining the popoverController property with retain, then you're getting a double-retain when you use the self.popoverController setter by assigning directly from the alloc. The general pattern for setting a #property is:
#property (nonatomic, retain) Foo* foo;
...
Foo* aFoo = [[Foo alloc] init];
self.foo = aFoo;
[aFoo release];
I have a strange problem that I've never encountered before,
I have data in my viewController that I want to display in a UIView.
It's an iPad App which involve a SplitView Controller, when I click on an element within the table view (masterView) it execute a function in my detailViewController (via a protocol).
A function is executed which launch a UIView and send data to it:
myController:
- (void)SelectionChanged:(DocumentInfo*)document_info withDocu:(Document *)document{
DocumentView *viewDoc=[[DocumentView alloc]initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
viewDoc.doc=document;
viewDoc.doc_info=document_info;
[viewDoc setBackgroundColor:[UIColor whiteColor]];
[self.view addSubview:viewDoc];
}
DocumentView.h
#import <UIKit/UIKit.h>
#import "Document.h"
#import "DocumentInfo.h"
#class Document;
#class DocumentInfo;
#interface DocumentView : UIView
#property(strong,nonatomic) Document *doc;
#property(strong,nonatomic) DocumentInfo *doc_info;
#end
DocumentView.m
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
UILabel *titreDoc=[[UILabel alloc] initWithFrame:CGRectMake(20, 32, 339, 21)];
titreDoc.textColor = [self makeColorRGB_RED:66 GREEN:101 BLUE:149];
titreDoc.font = [UIFont fontWithName:#"System" size:(24.0)];
[self addSubview:titreDoc];
NSLog(#"%# - %#",doc,doc_info);
titreDoc.text=#"Nouveau Document";
}
return self;
}
My view is well displayed (I mean the label appear) but impossible to get the data which would have been passed to it... (the NSLog print (null) (null) )
Anybody know the reason why?
The problem seems pretty straight forward. You initialize your view (which means that you run - (id)initWithFrame:(CGRect)frame) and after that you're setting the data, so it's normal that you see null values into your init method because the ivars have not being set yet. What you could do is to modify your init method in order to construct your view taking into account these ivars. Something like this perhaps:
- (id)initWithFrame:(CGRect)frame doc:(Document *)doc docInfo:(DocumentInfo *)docInfo;
ps. If you choose to make your custom init method do not forget to call the designated initializer (-initWithFrame:) before any customization.
The reason the NSLog prints null is because the doc and doc_info are nil when the initWithFrame method is called. The doc and doc_info properties are set after the initWithFrame method is called in selectionChanged: method. Add the NSLog function after line 3 in selectionChanged method like this:
- (void)SelectionChanged:(DocumentInfo*)document_info withDocu:(Document *)document{
DocumentView *viewDoc=[[DocumentView alloc]initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
viewDoc.doc=document;
viewDoc.doc_info=document_info;
NSLog(#"%# - %#",doc,doc_info);
[viewDoc setBackgroundColor:[UIColor whiteColor]];
[self.view addSubview:viewDoc];
}