Custom back button in UINavigationController

Snippet From Apple sample Code

UIImage *backButtonBackgroundImage = [UIImage imageNamed:@”back”];
    // The background should be pinned to the left and not stretch.
  float margin = 12.0;
    backButtonBackgroundImage = [backButtonBackgroundImage resizableImageWithCapInsets:UIEdgeInsetsMake(0, backButtonBackgroundImage.size.width – margin, 0, 0)];
    id appearance = [UIBarButtonItem appearanceWhenContainedIn:[
CustomBackButtonNavController class], nil];
    [appearance setBackButtonBackgroundImage:backButtonBackgroundImage forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
    UIBarButtonItem *backBarButton = [[UIBarButtonItem alloc] initWithTitle:@” ” style:UIBarButtonItemStylePlain target:nil action:nil];
    self.navigationItem.backBarButtonItem = backBarButton;

Just one note : the image you use may have different size an though needs different margin Value ;

Just another: CustomBackButtonNavController   can be replaced with UINavigationController in case you are using the same back button all over the app as in my most cases 🙂 .

Presenting ViewController from UIAlertView (Attempt to present on which is already presenting )

Presenting ViewController from UIAlertView
Something I face this morning which was annoying ,is That I was trying to present a ViewController
After user Tap on a UIAlertView button.
The result was this console log !!
uialertview Warning: Attempt to present <_UIModalItemsPresentingViewController: > on <_UIModalItemAppViewController:  > which is already presenting”
The Code I was using looked like this : 
UIAlertView * alert =[[[UIAlertView alloc] initWithTitle:TITLE
otherButtonTitles:nil] show];
And in The AlertView Delegate  I called presentViewController
-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
     MOImageViewController    *_imageVC =[[UIStoryboard storyboardWithName:@”Main” bundle:nilinstantiateViewControllerWithIdentifier:@”imageScreen”];
                    [_imageVC setImageURLString:urlString];
                    // topViewController  
                    [[self topViewController] presentViewController:_imageVC animated:YES completion:Nil];

What turned out is that UIAlertView is treated like viewController and upon clicking at one of its Buttons it gets dismissed, So in the previous code am presenting a new viewController while dismissing the AlertView Which gives me the mentioned warning .
The simplest solution for this is simply using another AlertView Delegate which is 
-(void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex{
 // presenting view controller here safely
Thats it 🙂