title: Singleton with ARC
body: <p>My question is the following: I have a singleton type object (I'm using ARC) that has this code in the implementation file</p>
  
  <pre><code>+(id)sharedInstance 
  {
      static DataManager *sharedInstance;
      if (sharedInstance == nil) {
          sharedInstance = [[DataManager alloc] init];
      }
      return sharedInstance;
  }
  
  +(NSManagedObjectContext *)getManagedContext
  {
      AppDelegate *applicationDelegate =(AppDelegate *)[[UIApplication sharedApplication] delegate];
      return [applicationDelegate managedObjectContext];
  }
  
  +(void)saveContext:(NSManagedObjectContext *)context
  {
      NSError *error;
      if (![context save:&amp;error]) {
          NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
      }
  }
  
  #pragma mark - Data management methods
  
  +(void)addPersonWithName:(NSString *)name andPicture:(UIImage *)picture
  {
      NSManagedObjectContext *context = [self getManagedContext]; //no problem here
      //some code 
      [self saveContex:context]; // no known class method for selector saveContext:
  }
  </code></pre>
  
  <p>Why is that? The method is declared in the .h file with + ... the <code>getManagedContext</code> model doesn't give this error???? </p>