Question

I have a navigation controller with a table view. In most tutorials I’ve read they usually have an array of view controllers (or subclasses of) stored locally in the table view controller that they use to push onto the navigation stack when a table cell is selected.

In my current project I have a lot of data that is loaded from an XML file. This data is kept central in a singleton class. This is my ‘model’ if you will.

So in my tableview controller I don’t have an array of view controllers (I didn’t want to have redundant data stored in my view controller when it’s already stored elsewhere). Instead I access the data from the singleton and create a view controller, initialize it with the appropriate data and then push that onto the navigation stack every time a table cell is selected.

This is a sample of the tableview:didselectrowatindexpath: method:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    DetailViewController *nextController = [[DetailViewController alloc] initWithNibName:@"DetailViewController" bundle:nil];

    // Here I setup some data from the singleton (just an example)
    nextController.title = [mySingleton.titles objectAtIndex:[indexPath row]];

    [self.navigationController pushViewController:nextController animated:YES]; 

    [nextController release];
}

So my question is does this approach have the potential to suffer performance loss? I’m worried about allocating and releasing memory every time the user selects a table cell. On the other hand, since I will potentially have a lot of data, I don’t want to have to repeat this data by storing it in an array of controllers.

I could always just have my singleton prepare the view controllers and store those instead of just the raw data. But I find it a bit weird that the model is always implicit in the controller. Is there a proper way of having the model stored independently of controller knowledge?

How would you approach this situation?

Thanks in advance.

Answer 1

Your approach is right.
In this line of code:

nextController.title = [mySingleton.titles objectAtIndex:[indexPath row]];

you are not “allocating and releasing” any data but the pointer’s data. nextController.title will point to some element inside mySingleton.titles. The data lives only inside your singleton’s class as long as you don’t call any copy method on the arrays.