Question

I am having a really hard time getting this to work. I have two view controllers with associated views called DomainSelectionViewController and DomainViewController. I’m going through a tutorial on Apple’s developer network that covers presenting view controllers. I’m getting an EXC_BAD_ACCESS signal when trying to run.

Here are the relevant excerpts from each file:

DomainSelectionViewController.h

@class DomainViewController;

@interface DomainSelectionViewController : UIViewController

- (IBAction)domainSelected:(id)sender;
- (IBAction)leaveDomain;

@property (retain) DomainViewController * selectedDomain;

@end

domainSelected: is attached to a button that represents a domain. Clicking on it successfully replaces the current view in the interface with the view defined in DomainViewController’s nib.

DomainSelectionViewController.m

@implementation
- (IBAction)domainSelected:(id)sender {
    NSLog(@"Domain Selected...");
    selectedDomain = [[DomainViewController alloc] initWithNibName:@"DomainView" bundle:nil];
    selectedDomain.domainSelectionContext = self;
    [self presentViewController:selectedDomain animated:NO completion:nil];
}

- (IBAction)leaveDomain {
    NSLog(@"Leaving Domain...");
    NSLog(@"Presented Domain: %@", self.presentedViewController);
    //selectedDomain.modalPresentationStyle = UIModalPresentationFullScreen;
    [self dismissViewControllerAnimated:NO completion:nil];
}

DomainViewController.h

#import <UIKit/UIKit.h>
#import "DomainSelectionViewController.h"

@class DomainSelectionViewController;

@interface DomainViewController : UIViewController

//@property (nonatomic, assign) DomainSelectionViewController * presentingViewController;
@property (nonatomic, retain) DomainSelectionViewController * domainSelectionContext;

@end

DomainViewController.m

- (IBAction)exit:(id)sender {
    NSLog(@"Leaving Domain...");
    if(self.presentingViewController) {
        NSLog(@"  Dismissing View Controller: %@.", self.presentingViewController);
        [self.domainSelectionContext leaveDomain];
        //[self.presentingViewController dismissViewControllerAnimated:NO completion:nil];
        return;
    }
    else {
        NSLog(@"Presenting view controller not set.");
    }
}

The domainview contains only one button that reads “back” and is connected to its own exit: function, which in turn calls leaveDomain on its delegate. It is on clicking on this button that the EXC_BAD_ACCESS call arises. Looking at other similar posts, it’s said that the EXC_BAD_ACCESS error typically arises from trying to call upon a deallocated object, but the print statement just before the dismiss call shows that the objects are still there and can be referred to. I was hoping someone with more experience than I could look at this and easily divine what has gone wrong.

For completeness’s sake, here’s the output from the console:

Attaching to process 26860.
2012-03-24 19:23:45.601 domaintest[26860:f803] DomainSelectionView Initialized.
2012-03-24 19:23:52.627 domaintest[26860:f803] Domain Selected...
2012-03-24 19:24:14.187 domaintest[26860:f803] Leaving Domain...
2012-03-24 19:24:14.188 domaintest[26860:f803]   Dismissing View Controller: <DomainSelectionViewController: 0x688f9a0>.
2012-03-24 19:24:14.188 domaintest[26860:f803] Leaving Domain...
2012-03-24 19:24:14.188 domaintest[26860:f803] Presented Domain: <DomainViewController: 0x6891d90>
Current language:  auto; currently objective-c
warning: Attempting to create USE_BLOCK_IN_FRAME variable with block that isn't in the frame.
(gdb)

Answer 1

So after quite a bit of trial-and-error, the issue here was higher up in the view hierarchy. The design had a root view controller that was completely empty, which replaced its own view with the first (DomainSelectionViewController) controller’s view

self.window.rootViewController.view = domainSelectionViewController.view;

The end result of which is that domainSelectionViewController could present domainViewController’s view, but trying to dismiss it resulted in EXC_BAD_ACCESS. I’m still not entirely sure why, but changing it such that domainSelectionViewController was the primary view, or having rootViewController present domainSelectionViewController in ViewDidAppear fixed the issue.