Iphone – Releasing subviews

iphone

I have a UIScrollView that has multiple pages of information that are added as subviews to the scrollView. Each subView's controller is stored in a NSMutableArray in the scrollViewController.

I have some memory leaks in the subviews, and I am trying to fix them by making sure that each subview controller's dealloc method is called. I'm doing that by releasing the view controllers from within the scrollView controller's dealloc method.

When I try to release the array after the subViews controllers are released, the application crashes.

Code follows… what am I doing wrong?

- (void)dealloc {

// Loop through the array of subView controllers and release them
for ( int i = 0; i < [viewControllers count]; i ++ ) {
    [[viewControllers objectAtIndex:i] release];
}

[viewControllers release];  // Crashes here unless I remove the loop above
[scrollView release];
[pageControl release];
[theKnot release];
[super dealloc];

}

Best Answer

NSMutableArray takes ownership of objects it contains -- it increments their reference counts when added, and will release its objects when it deallocates itself.

Assuming you released or autoreleased each view controller after you put it in your viewControllers array, there's no need loop over objects in viewControllers and release them -- the array will do it for you.

You're crashing when releasing the array because the array is trying to release objects that you already released and are now invalid.

Related Solutions

Objective-c – how to release uiview added as subview in scrollview

When you created your UIViewControllers you never released your own ownership of it, so until you release it yourself, it will never go away. The problem is that nothing else owns the UIViewControllers, so if you used autorelease, they would be deallocated right away.

My solution would be to create an NSMutableArray and add them to the array before calling release on them. Then, when you want to release all of your UIViewControllers, remove them from the array. NSMutableArray retains ownership of objects you add to it and releases ownership upon removal or deallocation. Something like this:

-(id) init {
    subViewControllers = [NSMutableArray new];
}
...
-(void)AddOneButton:(NSInteger)myButtonTag {
    ...
    if(categoryType==1) {
        MultiChoiceThumbViewControllerobj = [[MultiChoiceThumbViewController alloc] initWithPageNumber:myButtonTag+1];
        MultiChoiceThumbViewControllerobj.view.frame=frame2;
        MultiChoiceThumbViewControllerobj.lblCounter.text=[NSString stringWithFormat:@"%d of %d",myButtonTag+1,flashCardsId.count];
        MultiChoiceThumbViewControllerobj.lblQuestion.text=[flashCardText objectAtIndex:myButtonTag];
        [myScrollView addSubview:MultiChoiceThumbViewControllerobj.view];
        [subViewControllers addObjet:MultiChoiceThumbViewControllerobj];
        [MultiChoiceThumbViewControllerobj release];
    }
    [myScrollView addSubview:Button];
}
...
- (void) removeSuperviews {
    for(UIView *subview in [myScrollView subviews]) {
            [subview removeFromSuperview];
            NSLog(@"Subviews Count=%d",myScrollView.subviews.count);
    }
    [subViewControllers removeAllObjects];
}

R – MKMapView disposal

In dealloc, before releasing the mapView set its delegate to nil.

In addition, if you are using things like the ReverseGeocoder and a CLLocationManager you'll probably want to do the same thing.

Best Answer

Related Solutions

Objective-c – how to release uiview added as subview in scrollview

R – MKMapView disposal

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