Question

I have a Core Data backed table view, that show a list of editable fields, for different field types I have different UTableViewCells with different cell identifiers. When I scroll too quickly in the simulator or try to “bounce” past the last cell, I get a crash, saying that UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath. The whole problem goes away if I remove the dequeueReusableCellWithIdentifier: steps. Which means my table view is less efficient. I’m at most using 20 fetched objects (more along the lines of 8-10) in my table view, so the inefficiency might be a minor issue. I’d just like to know if I’m doing something the wrong way.

   - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

    Field *aField = [self.fetchedResultsController objectAtIndexPath:indexPath];
    static NSString *CellIdentifier = @"Cell";
    static NSString *ChoiceIdentifier = @"ChoiceCell";
    static NSString *SwitchIdentifier = @"SwitchCell";

    UITableViewCell *cell;

    if ([aField.fieldType isEqualToString:@"choice"] || [aField.fieldType isEqualToString:@"date"]  || [aField.fieldType isEqualToString:@"multiChoice"] ) {

        NSLog(@"ChoiceCell");
        cell = [tableView dequeueReusableCellWithIdentifier:ChoiceIdentifier];
        if (cell == nil) {
            if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
                [[NSBundle mainBundle] loadNibNamed:@"ChoiceTableViewCell-iPad" owner:self options:nil];
            } else {
                [[NSBundle mainBundle] loadNibNamed:@"ChoiceTableViewCell" owner:self options:nil];
            }
        }

    } else if ([aField.fieldType isEqualToString:@"boolean"]){

        NSLog(@"SwitchCell");
        cell = [tableView dequeueReusableCellWithIdentifier:SwitchIdentifier];
        if (cell == nil) {

            if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
                [[NSBundle mainBundle] loadNibNamed:@"SwitchTableViewCell-iPad" owner:self options:nil];
            } else {

                [[NSBundle mainBundle] loadNibNamed:@"SwitchTableViewCell" owner:self options:nil];
            }
        }


    } else {

        NSLog(@"Cell");
        cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
        if (cell == nil) {
            if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
                [[NSBundle mainBundle] loadNibNamed:@"EditableTableViewCell-iPad" owner:self options:nil];
            } else {

                [[NSBundle mainBundle] loadNibNamed:@"EditableTableViewCell" owner:self options:nil];
            }
        }
    } 

    cell = editableCell;
    self.editableCell = nil;


    // Configure the cell...
    [self configureCell:cell atIndexPath:indexPath];
    return cell;
}

Additional Details: The editableCell is being set as in each of the NIBs that correspond to the custom cells. I tried more directly setting this by saying

dynamicCell = [[[NSBundle mainBundle] loadNibNamed:@"ChoiceTableViewCell-iPad" owner:self options:nil] objectAtIndex:0];

but still had the same problem. It should never return nil. The all the NIBs are being loaded as long as I don’t scroll too fast. I’ve double and triple checked the NIB names to make sure.

Here’s the updated working code:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

{

Field *aField = [self.fetchedResultsController objectAtIndexPath:indexPath];
static NSString *CellIdentifier = @"Cell";
static NSString *ChoiceIdentifier = @"ChoiceCell";
static NSString *SwitchIdentifier = @"SwitchCell";


if ([aField.fieldType isEqualToString:@"choice"] || [aField.fieldType isEqualToString:@"date"]  || [aField.fieldType isEqualToString:@"multiChoice"] ) {

    NSLog(@"ChoiceCell");
    dynamicCell = [tableView dequeueReusableCellWithIdentifier:ChoiceIdentifier];
    if (dynamicCell == nil) {
        if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {


            [[NSBundle mainBundle] loadNibNamed:@"ChoiceTableViewCell-iPad" owner:self options:nil];
        } else {
            [[NSBundle mainBundle] loadNibNamed:@"ChoiceTableViewCell" owner:self options:nil];
        }
    }

} else if ([aField.fieldType isEqualToString:@"boolean"]){

    NSLog(@"SwitchCell");
    dynamicCell = [tableView dequeueReusableCellWithIdentifier:SwitchIdentifier];
    if (dynamicCell == nil) {

        if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
            [[NSBundle mainBundle] loadNibNamed:@"SwitchTableViewCell-iPad" owner:self options:nil];
        } else {

            [[NSBundle mainBundle] loadNibNamed:@"SwitchTableViewCell" owner:self options:nil];
        }
    }


} else {

    NSLog(@"Cell");
    dynamicCell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (dynamicCell == nil) {
        if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
            [[NSBundle mainBundle] loadNibNamed:@"EditableTableViewCell-iPad" owner:self options:nil];
        } else {

            [[NSBundle mainBundle] loadNibNamed:@"EditableTableViewCell" owner:self options:nil];
        }
    }
} 

UITableViewCell *cell;
cell = dynamicCell;
self.dynamicCell = nil;


// Configure the cell...
[self configureCell:cell atIndexPath:indexPath];
return cell;

}

Answer 1

Looks like the problem is with:

cell = editableCell

if editableCell is nil your app will crash. I assume you intend editableCell to be set by loadNibNamed:. It is not set if you dequeue a cell.