How to remove segmentedcontroller from uinavigationcontroller after view pops? - iphone

Question

I'm building a segmented control within my viewDidLoad method, like so:
NSArray *tabitems = [NSArray arrayWithObjects:#"ONE", #"TWO", nil];
UISegmentedControl *tabs = [[UISegmentedControl alloc] initWithItems:tabitems];
tabs.segmentedControlStyle = UISegmentedControlStyleBar;
tabs.frame = CGRectMake(185.0, 7.0, 130.0, 30.0);
tabs.selectedSegmentIndex = 0;
[self.navigationController.navigationBar addSubview:tabs];
[tabs release];
But when the user goes Back in the uinavigationcontroller hierarchy, the segmented controller stays on the navigation bar. How would I get rid of it? Or am I doing something fundamentally wrong?
EDIT
Following Alex's suggestions, I propertized tabs and tried:
NSArray *tabItems = [NSArray arrayWithObjects:#"FAQs", #"Terms", nil];
self.tabs = [[UISegmentedControl alloc] initWithItems:tabItems];
but I'm not sure it's a good idea to alloc a property;
And I'm using
[self.tabs removeFromSuperview];
in my viewWillDisappear. Is that enough?

Answer 1

Retain a reference to the segmented control in your view controller (i.e define tabs as a property in the view controller's header file).
Override the view controller's -viewWillDisappear: method, and remove the segmented control from the navigation bar there, using the control's -removeFromSuperview method.
EDIT
You would still alloc-init your segmented control tabs in -viewDidLoad. You just need to set up a retain property for tabs in your view controller's header, and move the control's release statement to the view controller's dealloc method.
Read the "Properties" section of this Objective-C tutorial for an introduction to properties and how to set them up.
The way to override a method is as follows:
- (ReturnClass) methodNameToOverride:args {
[super methodNameToOverride:args];
// your code goes here...
}
In the case of -viewWillDisappear:, this method gets called when your view controller is about to disappear, such as when it gets popped off the navigation stack. This is a great place to put code that manages clean-up of view-controller-specific items, like your segmented control:
- (void) viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
[tabs removeFromSuperview];
}
EDIT 2
If your property is set as follows:
#property (nonatomic, retain) UISegmentedControl *tabs;
then you are going to retain anything you set self.tabs equal to.
Your code here:
self.tabs = [[UISegmentedControl alloc] initWithItems:...];
will create a memory leak, because you are retaining this object: [[UISegmentedControl alloc] init] — but you never release [[UISegmentedControl alloc] init] itself. This is bad.
Instead, use autorelease on the right side, i.e.:
self.tabs = [[[UISegmentedControl alloc] initWithItems:...] autorelease];
The tabs property retains its own reference to the initialized segmented control. That initialized segmented control is itself released properly at some later point. So no more memory leak.

Answer 2

Even better, set the UISegmentedControl's owning UIViewController's navigationItem.titleView to the UISegmentedControl.
-(void) viewDidLoad {
if(!mySegmentedControl) {
// initialize the UISegmentedControl
...
}
self.navigationItem.titleView = mySegmentedControl;
}
No manual removal of the UISegmentedControl or any other UIView for that matter required except, of course, releasing when owning UIViewController is dealloc'ed. Also, to be a "good memory citizen", you might set your property to nil in -viewDidUnload.
You can also customize the left and right barButtonItems of the UIViewController's navgiationItem.