最后一行删除后如何重新加载自定义表格视图单元格？

Question

I have a UITableView with a simple array as data source. I designed a custom nib for a special UITableViewCell that is shown when the array is empty (ie when the app first starts).

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    if ([self.wallet count] == 0)
        return 1;
    else return [self.wallet count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    // If there isn't any coupon yet, then show the custom "No Coupon Yet" cell
    if ([self.wallet count] == 0)
        return [tableView dequeueReusableCellWithIdentifier:@"NoCouponCell" forIndexPath:indexPath];
    else {
        CouponCell *cell = [tableView dequeueReusableCellWithIdentifier:@"CouponCell" forIndexPath:indexPath];
        Coupon *coupon = [self.wallet objectAtIndex:indexPath.row];

        [cell configureForCoupon:coupon];
        return cell;
    }
}

Since I'd like to add the swipe-to-delete functionality, I provided the following method for the view controller.

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    [self.wallet removeObjectAtIndex:indexPath.row];
    // Creates a new, temporary array holding just the one index-path item
    NSMutableArray *tmp = [[NSMutableArray alloc] initWithObjects:indexPath, nil];
    // Tells the table view to delete the row with a nice animation
    [tableView deleteRowsAtIndexPaths:tmp withRowAnimation:UITableViewRowAnimationAutomatic];
}

However, when the table view has only one row and I try to delete it, my app crashes. Why?

EDIT: The debug info tells that a NSInternalInconsistencyException is raised.

Answer 1

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {

    if (editingStyle == UITableViewCellEditingStyleDelete) 
    {
        // Delete the row from the data source
        [self.wallet removeObjectAtIndex:indexPath.row];

        [tableView reloadData]; // reload your table to see updates

        // or if you what some animation use|

        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObjects:indexPath] 
                         withRowAnimation:UITableViewRowAnimationAutomatic];  

...

---

Here's a fix for your cellForRowAtIndexPath :

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

    CouponCell *cell = [tableView dequeueReusableCellWithIdentifier:[self.wallet count] == 0 ? @"NoCouponCell" : @"CouponCell" forIndexPath:indexPath];

    if ([self.wallet count] > 0)
    {
        Coupon *coupon = [self.wallet objectAtIndex:indexPath.row];

        [cell configureForCoupon:coupon];
    }
    return cell;
}

Answer 2

try this in your code:

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
        return [self.wallet count];
}

Answer 3

Use this in your numberOfRowsInSection function:

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{

      return [self.wallet count];
}

And at the end of your commitEditingStyle function, use

[tableView reloadData]; 

Answer 4

Try this piece of code:

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    [self.wallet removeObjectAtIndex:indexPath.row];
    // Creates a new, temporary array holding just the one index-path item
    NSMutableArray *tmp = [[NSMutableArray alloc] initWithObjects:indexPath, nil];
    // Tells the table view to delete the row with a nice animation
    [tableView beginUpdates];
    [tableView deleteRowsAtIndexPaths:tmp withRowAnimation:UITableViewRowAnimationAutomatic];
    [tableView endUpdates];
}

Answer 5

You are returning a rowcount of 1 if your data array wallet has no elements:

 if ([self.wallet count] == 0)
        return 1;
    else return [self.wallet count];

But in the commitEditingStyle method you don't handle this case: This means that it's possible to delete the NoCouponCell . And I assume that the crash occurs, because you want to remove an object from your data-array which does not exist.

[self.wallet removeObjectAtIndex:indexPath.row];

Solution : Use the following delegate method to determine when a cell can be edited: This prevents the delegate method commitEditingStyle to be called.

- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath{
    return [self.wallet count] > 0
}

Answer 6

you can add a view to the UITableview tableFooterView on tableview datasource, you can put your custome cell'content in this view

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    if (dataArray.count == 0) {
        UIView *view = [[UITableView alloc] initWithFrame:self.view.bounds];
        view.backgroundColor = [UIColor blueColor];
        self.tableView.tableFooterView = view;
    }
    return dataArray.count;
}