App running slow after loading viewcontroller, then unload about 15-20 times - ios

Question

Using:
Xcode 4.6
Storyboards
ARC
Model segue to SecondViewController
I have an app that has the main ViewController that loads a new veiwController when the device is rotated to the right. When the app starts everything works great. If I rotate the device, then back which unloads the secondview controller, about 15-20 times the app is very slugish. I have narrowed down that it only happenes when the seconed view controller is loaded and only when i rotate the device a nunmber of times. I also have narrowed down that is is a memory issue. I installed an app that keeps track of the memory used and available. My memory goes from 400mb to 900mb used when i rotate the device a number of times. I am trying to give as much info as I can. Each view has 8 NSTimers that fire every second.
Is there a way to programmatic unload a view, to make sure is is being unloaded?
I have included this code to ensure the loading and unloading:
`- (void)setView:(UIView *)aView
{
NSLog(#">>> Entering %s <<<", PRETTY_FUNCTION);
if (!aView) // view is being set to nil
{
NSLog(#"Should be unloading now");
}
[super setView:aView];
NSLog(#"<<< Leaving %s >>>", __PRETTY_FUNCTION__);
}
log result:
2013-04-22 16:42:03.588 xxxxxxxx[xxxxxxx] >>> Entering -[GraphViewController setView:] <<<
2013-04-22 16:42:03.589 xxxxxxxx[xxxxxxx] <<< Leaving -[GraphViewController setView:] >>>
`
I am not sure what I need to be looking at to correct this.
Any "points" in the right direction will be very appreciated .
Thanks

Answer 1

You haven't given much information about how you "unload" SecondViewController. Are you doing a modal segue to it as well? If so, that's your problem -- every time you do a segue, you instantiate a new view controller, and if these are modal segues, the presented controller has a strong pointer to the presenting controller, so none of these controllers will ever get deallocated as you go back and forth.
As a rule, you should never go backwards in a storyboard using anything but an unwind segue. So, the solution to your problem is to use an unwind segue to go from SecondViewController back to MainViewController -- this will actually go back to the same instance of MainViewController that you came from, and SecondViewController will be deallocated. If you don't know how to make an unwind segue, I will edit my answer to show you how.
After Edit:
To make an unwind segues, you do two things. In the controller that you're going back to, you add a method -- the two important things are that it be an IBAction, and that it has a single argument that's typed to UIStoryboardSegue*. It doesn't matter what you call it, and it doesn't even need to have any code inside it, though I usually put in a log statement just to be sure it's called. Then, in IB in the controller you're unwinding from, you control drag from your UI element like a button or table view cell (or from the controller itself if you want to fire it from code), down to the green Exit icon at the bottom of the scene -- it's important to note that you are dragging from a UI element to the exit icon in the same controller, not between controllers. When you let go of the drag over the exit icon, you will see any methods you created with the signature I mentioned above. Choose the one you want, and that's it. You can implement prepareForSegue in the source controller just like any other segue if you want to pass any information back to the destination controller.