Fetch latest app version from the app store.

FetchLatestAppVersionSnippets

+ (NSString *)applicationVersion {
    return  [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleShortVersionString"];
}

+ (void)showNeedUpdateAlertIfNeeded
{
    [self getLatestAppVersionAsynchronousWithCompletionBlock:^(NSString *latestAppVersion) {
        if ([latestAppVersion compare:[ApplicationInformation applicationVersion] options:NSNumericSearch] == NSOrderedDescending) {
            dispatch_async(dispatch_get_main_queue(), ^{
                // Show alert etc...
            });
        }
    }];
}

+ (void)getLatestAppVersionAsynchronousWithCompletionBlock:(void(^)(NSString *))completionBlock
{
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"http://itunes.apple.com/lookup?id=%@", kAppStoreID]]
                                             cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
                                         timeoutInterval:20.0];
    [NSURLConnection sendAsynchronousRequest:request
                                       queue:[[NSOperationQueue alloc] init]
                           completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
                               if (data) {
                                   NSDictionary *versionSummary = [NSJSONSerialization JSONObjectWithData:data
                                                                                                  options:NSJSONReadingAllowFragments
                                                                                                    error:&error];
                                   NSDictionary *results = [[versionSummary objectForKey:@"results"] objectAtIndex:0];
                                   NSString *latestVersion = [results objectForKey:@"version"];
                                   NSLog(@">>>>> Latest App Version is %@.", latestVersion);
                                   completionBlock(latestVersion);
                               } else {
                                   NSLog(@">>>>> Fail to Get Latest App Version.");
                               }
                           }];
}