Storyboard is creating multiple instances of my DetailViewController - iphone

Question

I started using storyboards but am noticing one very significant difference: The storyboard appears to be instantiating a new ViewController each time I navigate back and forth.
Example: I create two new Xcode projects based on the Master-Detail template. In Case 1, I use the Storyboard and in Case 2 I use the .xib.
Normally I would expect these to behave identically, but they don't!
In both of the DetailViewController.m I add the following method:
-(void)viewDidAppear:(BOOL)animated{
if (xposition ==0) {
xposition=50;
}else{
xposition = xposition+50;
}
NSLog(#"xposition update %d", xposition);
}
(I have also declared the xposition as an "int" instance variable in the header):
When I run the Storyboard version and tap the "+" and navigate in and out of the DetailViewController then my NSLog statement keeps giving me "xposition update 50".
By contrast, for the .xib version I get my expected behavior where each time I navigate in and out of the DetailViewController that the "position" increments by 50: so 50, 100, 150 etc.
How do I fix Storyboard to make it behave in the same way as the .xib based version. Specifically, I want to only instantiate the DetailViewController once.
EDIT: Answering my own question. I got some help on this and wanted to post the answer that worked for me.
When you first perform the segue store the destination viewcontroller in a property (see method "PrepareForSegue". My VC is called MyViewController)
Then create the delegate method called "shouldPerformSegueWithIdentifier" and use this to intercept the segue and manually present the stored ViewController for all subsequent segues.
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
UIViewController *destination = segue.destinationViewController;
NSLog(#"identifier = %#", [segue identifier]);
if([[segue identifier] isEqualToString:#"mySegue"]) {
self.myViewController = (MyViewController*)destination;
NSLog(#"Saving myViewController for later use.");
}}
- (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender {
if([identifier isEqualToString:#"mySegue"]) {
if(self.myViewController != nil) {
NSLog(#"Using the saved myViewController.");
[self.navigationController pushViewController:self.myViewController animated:YES];
return NO;
}else {
return YES;
}
}
return YES;}

Answer 1

When you navigate back and forth your storyboard pops off your DetailViewController. Because it is not retained by anything else it will be released, this is normal behavior.
If you want to keep the instance you'll have to retain it in the ViewController you are calling it from and use it later on again. Check this question for an example
Edit:
I think you solved the problem but here is an example:
Create a property for you viewcontroller in your interface, say myViewController
Retain the viewcontroller in the prepareForSegue method:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
[self setMyViewController:[segue destinationViewController]];
}
This it not leaking memory, your example could leak in some cases. Check out this guide here.
The next time the seque will be performed check if the property is already set and if so use it:
- (BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender {
if([self myViewController] != nil){
[[self navigationController] pushViewController:[self myViewController] animated:YES];
return NO;
}else{
return YES;
}
}