iOS5 to iOS4 crash - ViewControllers - iphone

Question

Currently I am trying to make my app available for iOS4, to increase the number of people we can reach.
We have moved away from StoryBoard and are now using .xib files instead.
Right now, the only thing that is stopping this is this error:
2012-09-14 18:32:42.705 CrunchCalculator[7037:11303] -[CategoryViewController presentViewController:animated:completion:]: unrecognized selector sent to instance 0x6b42230
2012-09-14 18:32:42.707 CrunchCalculator[7037:11303] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[CategoryViewController presentViewController:animated:completion:]: unrecognized selector sent to instance 0x6b42230'
*** Call stack at first throw:
(
0 CoreFoundation 0x013625a9 __exceptionPreprocess + 185
1 libobjc.A.dylib 0x00ef1313 objc_exception_throw + 44
2 CoreFoundation 0x013640bb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
3 CoreFoundation 0x012d3966 ___forwarding___ + 966
4 CoreFoundation 0x012d3522 _CF_forwarding_prep_0 + 50
5 CrunchCalculator 0x0002e560 +[OpenCalcViewController openCalcView:fromViewController:] + 8256
6 CrunchCalculator 0x0002fe0a -[CategoryViewController openCalc:] + 106
7 UIKit 0x002554fd -[UIApplication sendAction:to:from:forEvent:] + 119
8 UIKit 0x002e5799 -[UIControl sendAction:to:forEvent:] + 67
9 UIKit 0x002e7c2b -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527
10 UIKit 0x002e67d8 -[UIControl touchesEnded:withEvent:] + 458
11 UIKit 0x004e84de _UIGestureRecognizerSortAndSendDelayedTouches + 3609
12 UIKit 0x004e8c53 _UIGestureRecognizerUpdateObserver + 927
13 CoreFoundation 0x0134389b __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 27
14 CoreFoundation 0x012d86e7 __CFRunLoopDoObservers + 295
15 CoreFoundation 0x012a11d7 __CFRunLoopRun + 1575
16 CoreFoundation 0x012a0840 CFRunLoopRunSpecific + 208
17 CoreFoundation 0x012a0761 CFRunLoopRunInMode + 97
18 GraphicsServices 0x014b61c4 GSEventRunModal + 217
19 GraphicsServices 0x014b6289 GSEventRun + 115
20 UIKit 0x00263c93 UIApplicationMain + 1160
21 CrunchCalculator 0x0000276a main + 170
22 CrunchCalculator 0x000026b5 start + 53
)
terminate called throwing an exception(lldb)
Usually I use this to open another view:
UIViewController *controller;
controller = [[CategoryViewController alloc]initWithNibName:#"CategoryViewController" bundle:nil];
controller.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
[self presentModalViewController:controller animated:YES];
[controller release];
But in this case I call a function from a different file (for efficiency) using this code:
#import "AllofTheFiles.h"
+ (void)openCalcView: (NSString *)nameOfView fromViewController:(UIViewController *)controller {
NSUserDefaults *saveSpot = [NSUserDefaults standardUserDefaults];
UIViewController *modalController;
if ([nameOfView isEqualToString:#"Tax"]) {
modalController= [[TAXViewController alloc]initWithNibName:#"TAXViewController" bundle:nil];
}else if ([nameOfView isEqualToString:#"Rent"]){
modalController= [[RENTViewController alloc]initWithNibName:#"RENTViewController" bundle:nil];
} //... cut other else if's to save space
modalController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
[controller presentViewController:modalController animated:YES completion:nil];
[modalController release];
}
How can I fix this? Thanks in advance!

Answer 1

presentViewController:animated:completion: is available on iOS5 and above only, hence you get that crash.
Change the last part to:
modalController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
//do we support the new way of presenting a modal viewController?
if ([controller respondsToSelector:#selector(presentViewController:animated:completion:)])
{ //yes->so do it!
[controller presentViewController:modalController animated:YES completion:NULL];
}
else
{ //nope->we seem to be running on something prior to iOS5, do it the old way!
[controller presentModalViewController:modalController animated:YES];
}
[modalController release];
This will first check if the new way of presenting a viewController is supported. For making sure that this works fine in the future, as presentModalViewController: is marked as being deprecated, we only use that option if the new way is not available.

Answer 2

You may need to present a navcontroller, and/or use presentModalViewController, try the following:
UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:modalController];
navController.modalPresentationStyle = UIModalPresentationPageSheet;
navController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
[controller presentModalViewController:navController animated:YES completion:nil];
[modalController release];
[navController release];

Answer 3

The Till's solution is far the best.
But if, like me, you have numbers of present/DismissModalViewController: calls in your code, and doesn't want to duplicate the respondsToSelector test and is deprecated warnings over and over, just make UIViewController addition:
#implementation UIViewController (iOS4Compatibility)
- (void)presentViewController:(UIViewController *)viewControllerToPresent animated:(BOOL)flag {
if([self respondsToSelector:#selector(presentViewController:animated:completion:)])
[self presentViewController:viewControllerToPresent animated:flag completion:nil];
else
[self presentModalViewController:viewControllerToPresent animated:flag];
}
- (void)dismissViewControllerAnimated:(BOOL)flag {
if([self respondsToSelector:#selector(dismissViewControllerAnimated:completion:)])
[self dismissViewControllerAnimated:flag completion:nil];
else
[self dismissModalViewControllerAnimated:flag];
}
#end