Keeping a track of selected cells - iphone

Question

In my app, the user changes the fields that appear in a tableView depending on the cells selected by him/her. (FYI... I have permitted multiple cell selection.) Just when the user presses the back button, the program copies the textLabel of the selected cells to the placeholder of the parent viewController.
Here's the relevant section of my code:
- (void)willMoveToParentViewController:(UIViewController *)parent
{
int tempCount = 0;
for (int section = 0; section < 3; section++)
{
int rowMax;
if (section == 0)
rowMax = 3;
else if (section == 1)
rowMax = 5;
else if(section == 2)
rowMax = 3;
for(int row = 0; row < rowMax; row++)
{
NSIndexPath *tempIndexPath = [NSIndexPath indexPathForRow:row inSection:section];
UITableViewCell *selectedCell = [self.tableView cellForRowAtIndexPath:tempIndexPath];
if(selectedCell.accessoryType == UITableViewCellAccessoryCheckmark)
{
NSLog(#"tempCount = %d", tempCount);
tempCount++;
if (tempCount == 1)
chosenFieldsViewController.field0.placeholder = selectedCell.textLabel.text;
else if(tempCount == 2)
chosenFieldsViewController.field1.placeholder = selectedCell.textLabel.text;
else if(tempCount == 3)
chosenFieldsViewController.field2.placeholder = selectedCell.textLabel.text;
}
}
}
}
I realized that after selecting the cells if the tableView is scrolled down, the selected cells do not appear as placeHolder on the parentVC. From my analysis I think that once I scroll down, the cells are deleted from the memory. So despite the fact that the cells are selected, they fail to show up on the parent VC.
If so, why do I see the cells appear selected when I scroll up?
I would be grateful if somebody can suggest how I can keep a track of the selected cells even when the user scrolls.
Thanks.
Edit 1
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *selectedCell = [tableView cellForRowAtIndexPath:indexPath];
if(selectedCell.accessoryType != UITableViewCellAccessoryCheckmark && count<3)
{
selectedCell.accessoryType = UITableViewCellAccessoryCheckmark;
count ++;
}
else if(selectedCell.accessoryType == UITableViewCellAccessoryCheckmark)
{
selectedCell.accessoryType = UITableViewCellAccessoryNone;
count--;
}
}
Edit 2
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *CellIdentifier = [NSString stringWithFormat:#"CellForRow%dSection%d",indexPath.row, indexPath.section];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
}
cell.selectionStyle = UITableViewCellSelectionStyleNone; // VERY IMPORTANT
if (indexPath.section == 0)
{
switch(indexPath.row)
{
case 0:
cell.textLabel.text = #"Class A";
break;
case 1:
cell.textLabel.text = #"Class B";
break;
case 2:
cell.textLabel.text = #"Class C";
break;
default:
break;
}
}
if(indexPath.section == 1)
{
switch(indexPath.row)
{
case 0:
cell.textLabel.text = #"Class D";
break;
case 1:
cell.textLabel.text = #"Class E";
break;
case 2:
cell.textLabel.text = #"Class F";
break;
case 3:
cell.textLabel.text = #"Class G";
break;
case 4:
cell.textLabel.text = #"Class H";
break;
default:
break;
}
}
if(indexPath.section == 2)
{
switch (indexPath.row)
{
case 0:
cell.textLabel.text = #"Class I";
break;
case 1:
cell.textLabel.text = #"Class J";
break;
case 2:
cell.textLabel.text = #"Class K";
break;
default:
break;
}
}
return cell;
}

Answer 1

Declare a dictionary as,
#property (nonatomic, retain) NSMutableDictionary *selectedTextListDict;
In viewDidLoad,
NSMutableDictionary *selectedTextListDict = [[NSMutableDictionary alloc] init];
Then change these methods as,
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *selectedCell = [tableView cellForRowAtIndexPath:indexPath];
if(selectedCell.accessoryType != UITableViewCellAccessoryCheckmark && count < 3)
{
NSString *rowKeyString = [NSString stringWithFormat:#"%d", indexPath.row];
NSString *sectionKeyString = [NSString stringWithFormat:#"%d", indexPath.section];
NSMutableDictionary *row = [self.selectedTextListDict valueForKey:sectionKeyString];
if (!row) {
row = [[NSMutableDictionary alloc] init];
}
[row setObject:selectedCell.textLabel.text forKey:rowKeyString];
[self.selectedTextListDict setObject:row forKey:sectionKeyString];
selectedCell.accessoryType = UITableViewCellAccessoryCheckmark;
count ++;
}
else if(selectedCell.accessoryType == UITableViewCellAccessoryCheckmark)
{
NSString *rowKeyString = [NSString stringWithFormat:#"%d", indexPath.row];
NSString *sectionKeyString = [NSString stringWithFormat:#"%d", indexPath.section];
NSMutableDictionary *row = [self.selectedTextListDict valueForKey:sectionKeyString];
[row removeObjectForKey:rowKeyString];
if ([[row allKeys] count] == 0) {
[self.selectedTextListDict removeObjectForKey:sectionKeyString];
} else {
[self.selectedTextListDict setObject:row forKey:sectionKeyString];
}
selectedCell.accessoryType = UITableViewCellAccessoryNone;
count--;
}
}
- (void)willMoveToParentViewController:(UIViewController *)parent
{
NSArray *selectedTextSectionKeysList = [self.selectedTextListDict allKeys];
NSArray *sortedSelectedTextSectionKeysList = [selectedTextSectionKeysList sortedArrayUsingSelector:#selector(intValue)];
int tempCount = 0;
for (NSString *sectionString in sortedSelectedTextSectionKeysList) {
NSMutableDictionary *rowDict = [self.selectedTextListDict valueForKey:sectionString];
if (rowDict) {
NSArray *selectedTextRowKeysList = [rowDict allKeys];
NSArray *sortedSelectedTextRowKeysList = [selectedTextRowKeysList sortedArrayUsingSelector:#selector(intValue)];
for (NSString *rowString in sortedSelectedTextRowKeysList) {
tempCount++;
if (tempCount == 1)
chosenFieldsViewController.field0.placeholder = [rowDict valueForKey:rowString];
else if(tempCount == 2)
chosenFieldsViewController.field1.placeholder = [rowDict valueForKey:rowString];
else if(tempCount == 3)
chosenFieldsViewController.field2.placeholder = [rowDict valueForKey:rowString];
}
}
}
}
Edit 1:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if([segue.identifier isEqualToString:#"GoToModifyFieldsViewController"])
{
ModifyFieldsViewController *modifyFieldsViewController = segue.destinationViewController;
modifyFieldsViewController.chosenFieldsViewController = self;
field0.placeholder = #"";
field1.placeholder = #"";
field2.placeholder = #"";
if(self.selectedTextListDict)
self.selectedTextListDict = [[NSMutableDictionary alloc] init];
}
}
Declare a dictionary in ChosenFieldsViewController: as,
#property (nonatomic, retain) NSMutableDictionary *selectedTextListDict;
In viewDidLoad,
selectedTextListDict = [[NSMutableDictionary alloc] init];
Therefore, rather using self.selectedTextListDict, use: chosenFieldsViewController.selectedTextListDict in ModifyFieldsViewController.

Answer 2

-If so, why do I see the cells appear selected when I scroll up?
Because they get created automatically whenever they are about to appear. Every time you scroll up or down, cells get created or reused. When they disappear, they get destroyed or marked for reuse.