TableView Question

[Mick]

I am trying to allow the user of my software to empty out an array/UITableview (delete all items in the array and update the tableview that displays the array at the same time). I have managed to empty the array (actually a mutable array) with this:

[self.listData removeAllObjects];

I know it properly removes everything, because the array gets saved to a propertylist/file when the application closes, and upon reloading I can see the data was in fact deleted. However, the application crashes (sooner or later - doesn't always happen right away) if I try to scroll the tableview after emptying it, and I'm sure this is because I am not updating the tableview properly after emptying the array. I think I need to use a line like this:

[tableView deleteRowsAtIndexPaths:(NSArray *)indexPaths withRowAnimation:(UITableViewRowAnimation)animatio n];

to update the tableview, but I really don't understand how to use this method. I think I understand what an indexPath is, but how do I set up an array of them to make sure all data is deleted?

[Oliver Drobnik]

Originally Posted by Mick

I am trying to allow the user of my software to empty out an array/UITableview (delete all items in the array and update the tableview that displays the array at the same time). I have managed to empty the array (actually a mutable array) with this:


I know it properly removes everything, because the array gets saved to a propertylist/file when the application closes, and upon reloading I can see the data was in fact deleted. However, the application crashes (sooner or later - doesn't always happen right away) if I try to scroll the tableview after emptying it, and I'm sure this is because I am not updating the tableview properly after emptying the array. I think I need to use a line like this:


to update the tableview, but I really don't understand how to use this method. I think I understand what an indexPath is, but how do I set up an array of them to make sure all data is deleted?

That is most likely not your problem.

If you remove the contents of the array you use as data source you would probably call [myTableView reloadData]. This causes the table view to ask for how many rows there are now (0). So it will just draw a blank table.

The method you mention is good for animating the removal of single rows. So the pattern usually is: remove from NSArray, then make the table animate the removal.

I suspect your problem is that you are accessing memory that was previously released.

[Mick]

Thank you very much. I think my only remaining question is what to put for "myTableView" - I take it that is supposed to stand for the UItableview I am using - but I'm not sure what to call it in my software. Everything I try gives me an "undeclared" error (ie, if I use myTableView or just tableView, I get that error. I also tried self.tableView and that gave me an error saying there was no such structure).

Could the problem be that I did not declare an outlet for the tableview? I'm not sure if that is necessary or not. If that is not the problem, how do I figure out what to put for "myTableView"?

Maybe I should point out - I have been programming for a long time but I am very new to iPhone / objective C programming. I have been following a bunch of UITableView tutorials online, but I've had trouble making them work properly, at least in part because OS 2.2 seems to treat tableviews a little differently - or maybe just more strictly. Also, some tutorials start with projects based on the View-based template, some start with projects based on the Navigation-based template, and it's possible I have mixed and matched them improperly. In other words, perhaps there is something I left out that would have been generated automatically had I used the proper template.

Anyway, thanks again for your continued help!

Originally Posted by Oliver Drobnik

That is most likely not your problem.

If you remove the contents of the array you use as data source you would probably call [myTableView reloadData]. This causes the table view to ask for how many rows there are now (0). So it will just draw a blank table.

The method you mention is good for animating the removal of single rows. So the pattern usually is: remove from NSArray, then make the table animate the removal.

I suspect your problem is that you are accessing memory that was previously released.