Objective C - Problems With TableView Check Box Using Sections - ios

Question

I'm implementing a contact check-box feature in my UITableView by using the following code.
The problem I'm having is that, when checking off a couple of users and then scrolling up/down the table, users who should not be checked off are showing as checked, and vice versa.
I'm assuming it has something to do with an error in my cell creation, but I'm not quite sure what.
- (void)viewDidLoad {
...
self.checkedUsers = [[NSMutableArray alloc] init];
for (int i=0; i<self.allContacts.count; i++) {
[self.checkedUsers insertObject:#"FALSE" atIndex:i];
}
...
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *simpleTableIdentifier = #"SocietyContactCell";
SocietyContactCell *cell = (SocietyContactCell *)[tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
if (cell == nil) {
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:#"SocietyContactCell" owner:self options:nil];
cell = [nib objectAtIndex:0];
}
BOOL checked = [[self.checkedUsers objectAtIndex:indexPath.row] boolValue];
UIImage *image = (checked) ? [UIImage imageNamed:#"checkedContact.png"] : [UIImage imageNamed:#"uncheckedContact.png"];
[cell.checkButton setBackgroundImage:image forState:UIControlStateNormal];
[cell.checkButton addTarget:self action:#selector(buttonPressedAction:) forControlEvents:UIControlEventTouchUpInside];
}
- (void)buttonPressedAction:(id)sender
{
UIButton *button = (UIButton *)sender;
int row = button.tag;
BOOL checked = [[self.checkedUsers objectAtIndex:row] boolValue];
[self.checkedUsers removeObjectAtIndex:row];
[self.checkedUsers insertObject:(checked) ? #"FALSE":#"TRUE" atIndex:row];
UIImage *newImage = (checked) ? [UIImage imageNamed:#"uncheckedContact.png"] : [UIImage imageNamed:#"checkedContact.png"];
[button setBackgroundImage:newImage forState:UIControlStateNormal];
}
EDIT: I now realize the issue is likely coming from my use of sections in this TableView. The contacts are sorted into alphabetized sections, which is messing up my tags.
How would I tackle this problem using sections?

Answer 1

The problem here is retention of the status of checkmark in a cell. Since the table cells are reused on scrolling, the cellForRowAtIndexPath method is called again and the value of the check mark is not set again there.
You will have to make a global array which will store the status of the checkmark for each indexPath. Then you can set the status of the checkmark button checked/unchecked in cellForRowAtIndexPath method.
Add the following code snippet along with the code show:
[cell.checkButton addTarget:self action:#selector(buttonPressedAction:) forControlEvents:UIControlEventTouchUpInside];
[cell.checkButton setTag:indexPath.row];
Also, replace these lines:
[self.checkedUsers removeObjectAtIndex:row];
[self.checkedUsers insertObject:(checked) ? #"FALSE":#"TRUE" atIndex:row];
with this:
[self.checkedUsers replaceObjectAtIndex:row withObject:checked ? #"TRUE" : #"FALSE"];

Answer 2

In your SocietyContactCell Class add the following Method:
- (void)prepareForReuse {
[super prepareForReuse];
[self.checkButton setBackgroundImage:nil forState:UIControlStateNormal];
}

Answer 3

I don't see where you are setting button.tag every time in cellForRowAtIndexPath:, so the action method might be updating the wrong row in your self.checkedUsers array, although the action method independently updates the cell's image correctly at the moment. When you scroll up and down however, the display will go back to the state in the self.checkedUsers array.
You probably need a line like:
cell.checkButton.tag = indexPath.row;
in your cellForRowAtIndexPath: method.
Secondly, your action method is getting the state on self.itsToDoChecked, and then updating a self.checkedUsers array, when it appears it should be acting on the same array (simply reversing the state of the given row index). Not sure if that is just an example code typo or something significant.
Edit: It's also possible there is state in the cell subclass causing issues; hard to be sure. You want to implement -prepareForReuse in that class (and always call super) to reset any state to initial values.