title: objc_getAssociatedObject returning null
body: <p>I'm trying to pass an object using <code>objc_setAssociatedObject</code> </p>
  
  <p>I'm trying to pass <code>Evento</code> using the following code: </p>
  
  <pre><code>Evento *evento = (Evento*)[secAtt objectAtIndex:indexPath.row]; 
  objc_setAssociatedObject(evento, @"evento", self, OBJC_ASSOCIATION_RETAIN);
  </code></pre>
  
  <p>and later I'm trying to get this <code>evento</code> with the following code: </p>
  
  <pre><code>Evento *evento = objc_getAssociatedObject(self, "evento");
  </code></pre>
  
  <p>It returns <code>nil</code></p>
  
  <p>EDIT: some more code: </p>
  
  <pre><code> - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
  {
      UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];
      [cell setSelectionStyle:UITableViewCellSelectionStyleNone];
  
      NSString *sectionTitle = [sectionsTitles objectAtIndex:indexPath.section];
      NSArray *secAtt = [attractions objectForKey:sectionTitle];
  
      Evento *evento = (Evento*)[secAtt objectAtIndex:indexPath.row];
      objc_setAssociatedObject(self, @"evento", evento, OBJC_ASSOCIATION_RETAIN);
  
      NSString *tipoEntretenimento = evento.entretenimento.tipo.descricao;
      NSLog(@"tipo %@", tipoEntretenimento);
      UIImageView *imgCategoria = (UIImageView *)[cell.contentView viewWithTag:30];
     //[imgCategoria setContentMode:UIViewContentModeScaleAspectFit];
      if([tipoEntretenimento isEqualToString:@"Bares"])
          [imgCategoria setImage:[UIImage imageNamed:@"bares.png"]];
      else if ([tipoEntretenimento isEqualToString:@"Crianca"])
          [imgCategoria setImage:[UIImage imageNamed:@"crianca.png"]];
      else if ([tipoEntretenimento isEqualToString:@"Guloseimas"])
          [imgCategoria setImage:[UIImage imageNamed:@"guloseimas.png"]];
      else if ([tipoEntretenimento isEqualToString:@"Restaurantes"])
          [imgCategoria setImage:[UIImage imageNamed:@"restaurantes.png"]];
      else if ([tipoEntretenimento isEqualToString:@"Teatro"])
          [imgCategoria setImage:[UIImage imageNamed:@"teatro.png"]];
      else if ([tipoEntretenimento isEqualToString:@"Shows"])
          [imgCategoria setImage:[UIImage imageNamed:@"shows"]];
      else if ([tipoEntretenimento isEqualToString:@"Dança"])
          [imgCategoria setImage:[UIImage imageNamed:@"danca.png"]];
      else if ([tipoEntretenimento isEqualToString:@"Concertos"])
          [imgCategoria setImage:[UIImage imageNamed:@"concerto.png"]];
      else if ([tipoEntretenimento isEqualToString:@"Cinema"])
          [imgCategoria setImage:[UIImage imageNamed:@"cinema.png"]];
  
  
      UIFont *roboto = [UIFont fontWithName:@"Roboto-Bold" size:16];
      UILabel *lblNomeEvento = (UILabel *)[cell.contentView viewWithTag:10];
      lblNomeEvento.text = evento.entretenimento.nome;
      lblNomeEvento.font = roboto;
  
      Agenda *agenda = nil;
      if([evento.listaAgendas count] &gt; 0)
          agenda = (Agenda *)[evento.listaAgendas objectAtIndex:0];
  
      NSLog(@"agenda %@", agenda.description);
  
      UIImageView *imgevento = (UIImageView *)[cell.contentView viewWithTag:20];
      [imgevento setContentMode:UIViewContentModeScaleAspectFit];
      [imgevento setImage:[UIImage imageNamed:@"pin.png"]];
  
      UIButton *btnCompartilhar = (UIButton *)[cell.contentView viewWithTag:40];
      [btnCompartilhar.titleLabel setHidden:YES];
      btnCompartilhar.titleLabel.text = evento.entretenimento.nome;
      [btnCompartilhar addTarget:self action:@selector(compartilharClick:) forControlEvents:UIControlEventTouchDown];
  
  
      UIButton *btnFavoritar = (UIButton *)[cell.contentView viewWithTag:50];
      [btnFavoritar addTarget:self action:@selector(favoritarClick:) forControlEvents:UIControlEventTouchDown];
      return cell;
  }
  </code></pre>
  
  <p>and later when I'm trying to get the object: </p>
  
  <pre><code>-(void) compartilharClick:(id)sender {
      Evento *evento = (Evento *)objc_getAssociatedObject(self, "evento");
  
      UIActionSheet *popup = [[UIActionSheet alloc] initWithTitle:@"Compartilhar:" delegate:self cancelButtonTitle:@"Cancelar" destructiveButtonTitle:nil otherButtonTitles:
                              @"Facebook",
                              @"Google+",
                              @"Twitter",
                              @"Outros",
                              nil];
      popup.tag = 1;
      [popup showInView:[UIApplication sharedApplication].keyWindow];
  }
  </code></pre>