Error Handling in Xcode, iPhone SDK

Question

In Visual Basic, there's a line of code you can use to handle errors in code

"On Error Resume Next"

Is there something similar in Objective-C? My problem is I have an "Add New Cell" add button that creates a new cell during runtime. However, the cells are re-orderable. When you try to re-order the "Add New Cell" cell, I get an index out of bounds error. If I can just fix the error from occurring that would be great, but if there's an error handler I can use to just exit the move function when there is an error, that would be cool too.

Here is my moveRowAtIndexPath code:

- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
    iProfileAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
    [appDelegate moveFromOriginal:fromIndexPath.row toNew:toIndexPath.row];
}

Here is the error i receive:

*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSCFArray objectAtIndex:]: index (7) beyond bounds (7)'

Answer 1

This is an array bounds error and should be fixed.

Have you tried preventing the user from moving the "Add New Cell" cell?

To do this, implement tableView:canMoveRowAtIndexPath: and return NO for the "Add New Cell" cell row (YES for all other rows).

Answer 2

You can use try and catch. They are how objective c, and some others, handle exceptions. They will catch the "uncaught exception" similar to how I assume would "On Error Resume Next" works.

@try {
    /*this is where the code that might throw an exception goes*/
    [appDelegate moveFromOriginal:fromIndexPath.row toNew:toIndexPath.row];
}
@catch (NSException *exception) {
    /*add something here if you want it to do something special when the exception(or "error") is thrown*/
}
@finally {
    /*you don't have to include this finally part but if you do the code in it is excecuted weather the exception is thrown or not*/
}