AlertView Delegate with UIBackgroundFetchResult Crashing app

Question

I am trying to fetch new friend requests while the app is in the background. The fetch is working fine, its the alertView that is causing the app to crash. I believe its because of the incorrect delegate value that i am using, when i use delegate:nil then app doesn't crash.

Here is the storyboard of my app, the red arrow is where the fetchNewDataWithCompletionHandler code is being executed.

AppDelegate.m

#import "demo_AppDelegate.h"
#import "demo_Friends_ViewController.h"


@implementation demo_AppDelegate

-(void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler{
    NSDate *fetchStart = [NSDate date];
    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
    demo_Friends_ViewController *friends_vc = (demo_Friends_ViewController *) [storyboard instantiateViewControllerWithIdentifier:@"friendsTab"];
    [friends_vc fetchNewDataWithCompletionHandler:^(UIBackgroundFetchResult result) {
        completionHandler(result);
        NSDate *fetchEnd = [NSDate date];
        NSTimeInterval timeElapsed = [fetchEnd timeIntervalSinceDate:fetchStart];
        NSLog(@"Background Fetch Duration: %f seconds", timeElapsed);
    }];
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:2 * 1024 * 1024
                                                            diskCapacity:25 * 1024 * 1024
                                                                diskPath:nil];
    [NSURLCache setSharedURLCache:sharedCache];
    [application setMinimumBackgroundFetchInterval:UIApplicationBackgroundFetchIntervalMinimum];
    return YES;
}

demo_Friends_ViewController.h

#import <UIKit/UIKit.h>
#import <AddressBook/AddressBook.h>
#import <AddressBookUI/AddressBookUI.h>

@interface demo_Friends_ViewController : UIViewController <ABPeoplePickerNavigationControllerDelegate>

-(void)fetchNewDataWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler;
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex;

@end

demo_Friends_ViewController.m

-(void)fetchNewDataWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler{

    /* some code here for fetching */

    completionHandler(UIBackgroundFetchResultNewData);
    [UIApplication sharedApplication].applicationIconBadgeNumber = 1;

UIAlertView *alertView = [[UIAlertView alloc]
                                       initWithTitle:@"New Friend Request!"
                                       message:responseObject[@"message"]
                                       delegate:self
                                       cancelButtonTitle:@"Ignore"
                                       otherButtonTitles:@"Accept", nil] ;
             alertView.tag = 2;
             [alertView show];

then i have this method:

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {................}

but it seems like the compiler couldn't locate didDismissWithButtonIndex code method. Because as soon as i press any of Accept or Ignore buttons, the app crashes.

As you can see in my app there are four tabs: Home, Products, Friends and Account. Even if i select the Friends tab in simulator and then beings the Background Fetch Process, it still gets crashed. I also tried switching to tab bar using selectedIndex, but that is also not working.

I am stuck and lost, please advice, thank you.

Answer 1

In demo_Friends_ViewController.h, you forgot the UIAlertViewDelegate ;)

@interface demo_Friends_ViewController : UIViewController <ABPeoplePickerNavigationControllerDelegate, UIAlertViewDelegate>