Retrieving data from firebase database: code didn't go into the completion block or an error block
<p>I am trying to retrieve data  from database but my code didn't go into the completion block or an error block. I didn't want any auth authentication from user and save data in database from an app. Just  want to retrieve data from database. My database structure is like that</p>

<p><a href="https://i.stack.imgur.com/IUF5j.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/IUF5j.png" alt="enter image description here"></a></p>

<p>Here is the code </p>

<pre><code>- (void)viewDidLoad {
    [FIRDatabase database].persistenceEnabled = YES;
    [self referenceFromURL:@"https://project-8326407164650950213.firebaseio.com"];
}
- (FIRDatabaseReference *) referenceFromURL:(NSString *)databaseUrl{

    commentsRef = [[FIRDatabase database] referenceFromURL:databaseUrl];
    return commentsRef;
}


-(void)viewWillAppear:(BOOL)animated
{
    [[commentsRef child:@"Hello"]
     observeEventType:FIRDataEventTypeValue
     withBlock:^(FIRDataSnapshot *snapshot) {
         NSDictionary * post = snapshot.value;

     }withCancelBlock:^(NSError * error){
         NSLog(@"%@",error.description);
     }];
}
</code></pre>

<p>Tell me what I am missing in that code. </p>