Question

I have a problem with memory management. A have a scrollview and every page in it loads from array of view controllers.
I load scrolview page calling the folowing method:

- (void)loadScrollViewWithPage:(int)page {

    if (page < 0) return;
    if (page >= kNumberOfPages) return;


    BancaTableViewController *controller = [viewControllers objectAtIndex:page];


    if ((NSNull *)controller == [NSNull null]) {

        controller=[[BancaTableViewController alloc] initWithPageNumber:page];
        controller.banks=banks;
        [controllersetDelegate:self];
        [viewControllers replaceObjectAtIndex:page withObject:controller];
        [controller release];
    }

    // add the controller's view to the scroll view
    if (nil == controller.view.superview) {
        CGRect frame = scrollView.frame;
        frame.origin.x = frame.size.width * page;
        frame.origin.y = 0;
        controller.view.frame = frame;
        [scrollView addSubview:controller.view];
    }


}

This is my unload view controller method which unloads all controllers except the controller of curent page but it doesn’t seem to work because the memory keep increasing.

- (void)unloadScrollViewWithPage:(int)page {
    for (unsigned i = 0; i < kNumberOfPages; i++) {
      if(i!=page){
       [viewControllers replaceObjectAtIndex:i withObject:[NSNull null]];
      }
    }
}

How to write the unloadviewcontroller correctly?

Answer 1

You’re adding a hard pointer to scrollView, but you never remove the object. (i.e. you keep adding subViews to scrollView and never remove them.

[scrollView addSubview:controller.view];

Try this…

Add a tag to your controller view when you add them to the scrollView, then remove it before you load a new controller. Check syntax – from memory – not tested

if ((NSNull *)controller == [NSNull null]) {

    controller=[[BancaTableViewController alloc] initWithPageNumber:page];
    controller.banks=banks;
    controller.tag = 3;
    [controllersetDelegate:self];
    [viewControllers replaceObjectAtIndex:page withObject:controller];
    [controller release];
}

// add the controller's view to the scroll view
if (nil == controller.view.superview) {
    CGRect frame = scrollView.frame;
    frame.origin.x = frame.size.width * page;
    frame.origin.y = 0;
    controller.view.frame = frame;
    [scrollView removeFromView:[scrollView viewWithTag:3]];
    [scrollView addSubview:controller.view];
}