remove objects of selected row - ios

Question

hey i have created a table view with multiple selection and checkmark accessory which users can tap on and select relevant rows in table... retailerid and retailernaem of individual selection will be stored in NSMutableDictionary and all dictionaries in return will be stored in NSMutableArray... i have done this till now
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *selectedCell = [tableView cellForRowAtIndexPath:indexPath];
if ([selectedCell accessoryType] == UITableViewCellAccessoryNone) {
[selectedCell setAccessoryType:UITableViewCellAccessoryCheckmark];
NSMutableDictionary *theDictionary = [[NSMutableDictionary alloc] init];
[theDictionary setObject:[[BrandsArray valueForKey:#"RetailerID"] objectAtIndex:indexPath.row] forKey:#"id"];
[theDictionary setObject:[[BrandsArray valueForKey:#"RetailerName"] objectAtIndex:indexPath.row] forKey:#"name"];
[selectedIndexes addObject:theDictionary];
}
else {
[selectedCell setAccessoryType:UITableViewCellAccessoryNone];
NSLog(#"this is deselected row %#",[selectedIndexes objectAtIndex:indexPath.row]);
NSMutableDictionary *dictionary = [selectedIndexes objectAtIndex:indexPath.row];
[selectedIndexes removeObject:dictionary];
dictionary = nil;
}
[tableView deselectRowAtIndexPath:indexPath animated:NO];
}
now problem is in the else block... its not removing objects from randomly selected row...
for example if i select first row and then deselect the same it works fine but when i select the last row and then deselect the same app crash..

Answer 1

Since my other answer dealt with multiple sections, I will provide a simpler, single section answer here
First, declare a property for your selection state -
#property (strong,nonatomic) NSMutableIndexSet *selectStates;
Initialise it in viewDidLoad
self.selectStates=[NSMutableIndexSet new];
The use it in didSelectRowAtIndexPath -
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *selectedCell = [tableView cellForRowAtIndexPath:indexPath];
if ([self.selectStates containsIndex:[indexPath.row]) {
[selectedCell setAccessoryType:UITableViewCellAccessoryNone];
[self.selectStates removeIndex:indexPath.row];
} else {
[selectedCell setAccessoryType:UITableViewCellAccessoryCheckmark];
[self.selectStates addIndex:indexPath.row];
}
[tableView deselectRowAtIndexPath:indexPath animated:NO];
}
You will also need to check the selectedStates in cellForRowAtIndexPath to set the correct accessory when the cell is scrolled back into view. Just add the snippet -
if ([self.selectStates containsIndex:[indexPath.row]) {
[cell setAccessoryType:UITableViewCellAccessoryNone];
} else {
[cell setAccessoryType:UITableViewCellAccessoryCheckmark];
}
If you need the ability to easily insert and delete rows then you can use an NSMutableSet instead of an NSIndexSet - just store the data source object. If you do allow deletion you need to make sure that the object is removed from the set, if necessary, when the row is deleted.
First, declare a property for your selection state -
#property (strong,nonatomic) NSMutableSet *selectStates;
Initialise it in viewDidLoad
self.selectStates=[NSMutableSet new];
The use it in didSelectRowAtIndexPath -
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *selectedCell = [tableView cellForRowAtIndexPath:indexPath];
Brand *brand=(Brand *)[BrandsArray objectAtIndex:indexPath.row]; // Change "Brand" to the appropriate object class
if ([self.selectStates containsObject:brand) {
[selectedCell setAccessoryType:UITableViewCellAccessoryNone];
[self.selectStates removeObject:brand];
} else {
[selectedCell setAccessoryType:UITableViewCellAccessoryCheckmark];
[self.selectStates addObject:brand];
}
[tableView deselectRowAtIndexPath:indexPath animated:NO];
}
You will also need to check the selectedStates in cellForRowAtIndexPath to set the correct accessory when the cell is scrolled back into view. Just add the snippet -
if ([self.selectStates containsObject:brand) {
[cell setAccessoryType:UITableViewCellAccessoryNone];
} else {
[cell setAccessoryType:UITableViewCellAccessoryCheckmark];
}

Answer 2

The problem is the way you use the array.
Let's say you select the last element from a table view with 10 cells. Then the array size is 1, but when you select again the last row, [selectedIndexes objectAtIndex:indexPath.row]; is trying to access the element with index 9 in the array, which does not exist at the moment.
Try to implement something like this:
NSInteger ARRAY_INITIAL_SIZE = 100;
NSMutableArray *selectedIndexes = [NSMutableArray arrayWithCapacity:ARRAY_INITIAL_SIZE];
for (NSInteger i = 0; i < ARRAY_INITIAL_SIZE; ++i) {
selectedIndexes[i] = [NSNull null];
}
Make selectedIndexes to be a property in your View Controller class, and whenever you use it, put self.selectedIndexes instead.
In the didSelectRow: atIndexPath: method, the first line is recommended to be:
[tableView deselectRowAtIndexPath:indexPath animated:NO];
Then, write the code:
UITableViewCell *selectedCell = [tableView cellForRowAtIndexPath:indexPath];
if ([selectedCell accessoryType] == UITableViewCellAccessoryNone) {
selectedCell.accessoryType = UITableViewCellAccessoryCheckmark;
NSMutableDictionary *theDictionary = [NSMutableDictionary dictionary];
[theDictionary setObject:[[BrandsArray valueForKey:#"RetailerID"] objectAtIndex:indexPath.row] forKey:#"id"];
[theDictionary setObject:[[BrandsArray valueForKey:#"RetailerName"] objectAtIndex:indexPath.row] forKey:#"name"];
[selectedIndexes replaceObjectAtIndex:indexPath.row withObject:theDictionary];
} else {
selectedCell.accessoryType = UITableViewCellAccessoryNone;
[selectedIndexes replaceObjectAtIndex:indexPath.row withObject:[NSNull null]];
}
I hope it helps you. Let me know.