Why is UITableViewCell not reloaded properly? - objective-c

Question

I´m loading a bunch of countries to a table and allowing the user to delete. The rows directly correspond to the countries array, by using objectAtIndex:indexPath.row and I set the delete button´s tag to the same index.
When I delete the first couple of rows it´s ok but afterwards the wrong rows are getting deleted and the app crashes.
Here's how I create rows:
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell;
NSString *currentText;
// fill in country cell content
if ([tableView tag] == 400) {
cell = [tableView dequeueReusableCellWithIdentifier:#"SettingsCountryCell"];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:#"SettingsCountryCell"];
NSLog(#"is nil");
} // it´s never nil
currentText = [arrSelectedCountries objectAtIndex:indexPath.row];
int currentRow = indexPath.row;
UILabel *countryLabel = (UILabel *)[cell viewWithTag:401];
countryLabel.text = currentText;
// create button
UIButton *countryButton = (UIButton *)[cell viewWithTag:402];
[countryButton setTag:currentRow];
[countryButton setTitle:[NSString stringWithFormat:#"row%d", currentRow]
forState:UIControlStateNormal];
NSLog(#"%# - tag %d - title %# - button tag %d",
currentText,
currentRow,
countryButton.titleLabel.text,
countryButton.tag);
// on load: Bulgaria - tag 2 - title row2 - button tag 2
// after one deletion (and ever after):
// Bulgaria - tag 1 - title (null) - button tag 0
[countryButton addTarget:self
action:#selector(removeCountry:)
forControlEvents:UIControlEventTouchUpInside];
}
Here's how I remove them (i.e. countries):
- (void)removeCountry:(UIButton *)countryButton
{
// removed country
NSString *currentText = [arrSelectedCountries objectAtIndex:countryButton.tag];
NSLog(#"removed country %# at tag %d", currentText, countryButton.tag);
// ok: removed country All CEE Countries at tag 0
// ok: removed country Bulgaria at tag 0
// not ok: removed country Czech Republic at tag 1
// add to picker selection and remove from selected
[arrCountries addObject:currentText];
[arrSelectedCountries removeObject:currentText];
// refresh picker and country table
[countryPicker reloadAllComponents];
[countryTable reloadData];
[countryTable reloadSections:[NSIndexSet indexSetWithIndex:0]
withRowAnimation:UITableViewRowAnimationFade];
// position table and elements below it
[self repositionForCountryChange];
}
At first the table is showing: row0, row1, row2, etc.
After a couple of deletions: row1, row2, row3, etc.
Once this happens, the label is no longer corresponding properly to the tag. When I click delete on Croatia, delete button labeled row 1, NSLog says:
removed country Czech Republic at tag 1
... and Croatia row is not deleted although its delete button now says row2.
And why am I getting from NSLog:
title (null) - button tag 0
...when I can see in the table that there is a title and removeCountry can access button tag, although incorrectly?

Answer 1

You have set up the button with a tag to allow you to identify it as a subview in the cell (402) you then change the tag so it identifies the row the tag is in. When the cell is re-used, there is no view with tag 402, so your button is still identified with a tag number of its original row.
You're using tags for two purposes. Ideally, don't use them at all as they are fragile and do not make your code readable.
create a UITableViewCell subclass and identify its subviews using outlets
identify the row of the pressed button using the method I describe here which is much more flexible than tags and keeps working if you delete rows.