Multiple checkbox in tableview iOS Objective-C - objective-c

Question

Im working on Multiple checkbox Functionality in tableview, I have to search in google finally i got it one solution.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];
}
if ([selectedRowsArray containsObject:[contentArray objectAtIndex:indexPath.row]]) {
cell.imageView.image = [UIImage imageNamed:#"checked.png"];
}
else {
cell.imageView.image = [UIImage imageNamed:#"unchecked.png"];
}
UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleChecking:)];
[cell.imageView addGestureRecognizer:tap];
cell.imageView.userInteractionEnabled = YES; //added based on #John 's comment
//[tap release];
cell.textLabel.text = [contentArray objectAtIndex:indexPath.row];
return cell;
}
- (void) handleChecking:(UITapGestureRecognizer *)tapRecognizer {
CGPoint tapLocation = [tapRecognizer locationInView:self.tableView];
NSIndexPath *tappedIndexPath = [self.tableView indexPathForRowAtPoint:tapLocation];
if ([selectedRowsArray containsObject:[contentArray objectAtIndex:tappedIndexPath.row]]) {
[selectedRowsArray removeObject:[contentArray objectAtIndex:tappedIndexPath.row]];
}
else {
[selectedRowsArray addObject:[contentArray objectAtIndex:tappedIndexPath.row]];
}
[self.tableView reloadRowsAtIndexPaths:[NSArray arrayWithObject:tappedIndexPath] withRowAnimation: UITableViewRowAnimationFade];
}
In that code i have one doubt. what is selectedRowsArray and what is ContentArray Please explain anyone. Thanks in advance.

Answer 1

The selectedRowsArray is another array maintained beside your contentArray which is used to hold the content for of the cells that are currently selected in the UITableView. The contentArray holds the actual content which is populated the cells.
Make note of the following lines:
if ([selectedRowsArray containsObject:[contentArray objectAtIndex:indexPath.row]])
{
cell.imageView.image = [UIImage imageNamed:#"checked.png"];
}
else
{
cell.imageView.image = [UIImage imageNamed:#"unchecked.png"];
}
The cell contents are checked for their presence in the selectedRowsArray which means that the cell is selected.
The selection and deselection is handled by the handleChecking: method which adds or removes the object from the same index in the contentArray into the selectedRowsArray.
You must have understood by now that cells in a UITableView are reused, so the actual number of UITableViewCells in the memory are most probably less than the number of cells to be shown in the UITableView. Hence the need for a system which can actually determine whether the cell is currently selected so this status can be populated when the cell is rendered again in the view.
Alternative methods to achieve the same involve using Booleans in an array representing the status of each cell, or simply the indexes of each selected cell in an array.