UIViewController may not respond to showRootPopoverButtonItem

Question

I am using Apple's MuiltipleDetailViewController sample app and get the message "UIViewController may not respond to showRootPopoverButtonItem"

This worked in XCode 3.X, but I get the message with 4.2

The app itself functions 100%, the popover is recognized in every nib, as is the table on the left when in landscape mode. But I can't submit with this warning. What do I need to change??

RootViewController.h

#import <UIKit/UIKit.h>


/*
 SubstitutableDetailViewController defines the protocol that detail view controllers must adopt. The protocol specifies methods to hide and show the bar button item controlling the popover.

 */
@protocol SubstitutableDetailViewController <NSObject>
- (void)showRootPopoverButtonItem:(UIBarButtonItem *)barButtonItem;
- (void)invalidateRootPopoverButtonItem:(UIBarButtonItem *)barButtonItem;
@end


@interface RootViewController : UITableViewController <UISplitViewControllerDelegate> {

    UISplitViewController *splitViewController;

    UIPopoverController *popoverController;    
    UIBarButtonItem *rootPopoverButtonItem;

    //UINavigationBar *navigationBar;
}

@property (nonatomic, assign) IBOutlet UISplitViewController *splitViewController;

@property (nonatomic, retain) UIPopoverController *popoverController;
@property (nonatomic, retain) UIBarButtonItem *rootPopoverButtonItem;


//@property (nonatomic, retain) IBOutlet UINavigationBar *navigationBar;

@end

RootViewController.m:

#import "RootViewController.h"
#import "WebViewController.h"
#import "Twitter.h"
//#import "SubstitutableDetailViewController.h"



@implementation RootViewController

@synthesize splitViewController, popoverController, rootPopoverButtonItem;//, navigationBar;


#pragma mark -
#pragma mark View lifecycle

- (void)viewDidLoad {

    [super viewDidLoad];
    // Set the content size for the popover: there are just two rows in the table view, so set to rowHeight*2.
    self.contentSizeForViewInPopover = CGSizeMake(310.0, self.tableView.rowHeight*2.0);
    //self.navigationController.navigationBar.tintColor = [UIColor colorWithRed:255/255 green:104/255 blue:1/255 alpha:1];
}
/*
-(void)customizeAppearance {
    //create resizable images
    UIImage *bluImage = [UIImage imageNamed:@"blu.jpg"];// resizableImageWithCapInsets:(0, 0, 0, 0)];

    //set the bg for *all* UINavBars
    [[UINavigationBar appearance] setBackgroundImage:bluImage forBarMetrics:UIBarMetricsDefault];
}
 */

-(void) viewDidUnload {
    [super viewDidUnload];

    self.splitViewController = nil;
    self.rootPopoverButtonItem = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    return YES;
}


- (void)splitViewController:(UISplitViewController*)svc willHideViewController:(UIViewController *)aViewController withBarButtonItem:(UIBarButtonItem*)barButtonItem 
       forPopoverController:(UIPopoverController*)pc {

    // Keep references to the popover controller and the popover button, and tell the detail view controller to show the button.
    barButtonItem.title = @"Index";
    self.popoverController = pc;
    self.rootPopoverButtonItem = barButtonItem;
    UIViewController <SubstitutableDetailViewController> *detailViewController = [splitViewController.viewControllers objectAtIndex:1];
    [detailViewController showRootPopoverButtonItem:rootPopoverButtonItem];
}


- (void)splitViewController:(UISplitViewController*)svc willShowViewController:(UIViewController *)aViewController 
  invalidatingBarButtonItem:(UIBarButtonItem *)barButtonItem {

    // Nil out references to the popover controller and the popover button, and tell the detail view controller to hide the button.
    UIViewController <SubstitutableDetailViewController> *detailViewController = [splitViewController.viewControllers objectAtIndex:1];
    [detailViewController invalidateRootPopoverButtonItem:rootPopoverButtonItem];
    self.popoverController = nil;
    self.rootPopoverButtonItem = nil;
}


#pragma mark -
#pragma mark Table view data source

- (NSInteger)tableView:(UITableView *)aTableView numberOfRowsInSection:(NSInteger)section {

    // Two sections, one for each detail view controller.
    return 2;
}


- (UITableViewCell *)tableView:(UITableView *)aTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *CellIdentifier = @"RootViewControllerCellIdentifier";

    // Dequeue or create a cell of the appropriate type.
    UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        //cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    }

    // Set appropriate labels for the cells.
    if (indexPath.row == 0) {
        cell.textLabel.text = @"Twitter";
    }

    else if (indexPath.row == 1) {
        cell.textLabel.text = @"Contact Us";
    }


    cell.textLabel.textColor = [UIColor whiteColor];
    cell.textLabel.backgroundColor = [UIColor blackColor];
    cell.contentView.backgroundColor = [UIColor blackColor];
    cell.detailTextLabel.backgroundColor = [UIColor blackColor];
    return cell;
}


#pragma mark -
#pragma mark Table view selection

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    /*
     Create and configure a new detail view controller appropriate for the selection.
     */
    NSUInteger row = indexPath.row;

    UIViewController *detailViewController = nil;

    if (row == 0) {
        Twitter *newDetailViewController = [[Twitter alloc] 
                                                      initWithNibName:@"Twitter" 
                                                      bundle:nil];
        detailViewController = newDetailViewController;
    }    

    if (row == 1) {
        WebViewController *newDetailViewController = [[WebViewController alloc] 
                                                      initWithNibName:@"WebViewController" 
                                                      bundle:nil];
        newDetailViewController.detailURL=
        [[NSURL alloc] initWithString:@"http://www.chipmunkmobile.com/contact.html"];

        detailViewController = newDetailViewController;
    }   

    // Update the split view controller's view controllers array.
    NSArray *viewControllers = [[NSArray alloc] initWithObjects:self.navigationController, detailViewController, nil];
    splitViewController.viewControllers = viewControllers;
    [viewControllers release];

    // Dismiss the popover if it's present.
    if (popoverController != nil) {
        [popoverController dismissPopoverAnimated:YES];
    }

    // Configure the new view controller's popover button (after the view has been displayed and its toolbar/navigation bar has been created).
    if (rootPopoverButtonItem != nil) {
        [detailViewController showRootPopoverButtonItem:self.rootPopoverButtonItem];
    }


    [detailViewController release];
}

#pragma mark -
#pragma mark Managing the popover


/*
- (void)showRootPopoverButtonItem:(UIBarButtonItem *)barButtonItem {
    // Add the popover button to the left navigation item.
    [navigationBar.topItem setLeftBarButtonItem:barButtonItem animated:NO];
}


- (void)invalidateRootPopoverButtonItem:(UIBarButtonItem *)barButtonItem {
    // Remove the popover button.
    [navigationBar.topItem setLeftBarButtonItem:nil animated:NO];
}
 */

#pragma mark -
#pragma mark Memory management

- (void)dealloc {
    [popoverController release];
    [rootPopoverButtonItem release];
    [super dealloc];
}

@end

Here is an image of the exact line where I get the warning

Answer 1

The reason you getting this warning is because of this UIViewController *detailViewController UIViewController does not have a method called "showRootPopoverButtonItem". If you want to get rid of the warning just do this instead:

[(WebViewController*)detailViewController showRootPopoverButtonItem:self.rootPopoverButtonItem];

or

[(Twitter*)detailViewController showRootPopoverButtonItem:self.rootPopoverButtonItem];

You just need to let it know its not really just a viewController, its a subclassed viewController you created. So what ever class showRootPopoverButtonItem: is in you just need to type cast it.