Table View Controller Cell Check Mark - ios

Question

I am new at objective-c coding. I was trying to implement a check mark on a table view controller. I want check mark to seen when i click on a cell, and disappear when i re-click on that cell.
For example i found this code below. But i don't understand one thing clearly. What does "data" and "checkData" means ? Do we have to set them before that code ?
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
// do usual stuff here including getting the cell
// determine the data from the IndexPath.row
if (data == self.checkedData)
{
cell.accessoryType = UITableViewCellAccessoryCheckmark;
} else {
cell.accessoryType = UITableViewCellAccessoryNone;
}
return cell; }
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
// determine the selected data from the IndexPath.row
if (data != self.checkedData) {
self.checkedData = data;
}
[tableView reloadData]; }
So I was searching for some codes and i couldn't find any code as i want.
I will be very happy for any help.
Thanks.

Answer 1

The code you posted is not good for general purposes.
To support multiple cell selections, you need an extra data structure (e.g. an array of booleans or an NSIndexSet) to keep track of the selected indexes. And then, as soon as you get the tableView:didSelectRowAtindexPath: update the data structure and force the reload of the table, i.e. [self.tableView reloadData] in order to show/hide selection checkmarks
Some chunks of code
#implementation TableViewController {
NSArray * _data;
NSMutableIndexSet *_selectedIndexes;
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
...
self.selectedIndexes = [[NSMutableIndexSet alloc] init];
...
return self;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
if ([_selectedIndexes containsIndex:indexPath.row]) {
[_selectedIndexes removeIndex:indexPath.row];
} else {
[_selectedIndexes addIndex:indexPath.row];
}
[tableView reloadData];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
....
if ([_selectedIndexes containsIndex:indexPath.row])
{
cell.accessoryType = UITableViewCellAccessoryCheckmark;
} else {
cell.accessoryType = UITableViewCellAccessoryNone;
}
...
return cell;
}
Note that NSMutableIdexSet must have the same length of NSArray representing the data structure you're using to populate tableView's cells.
Alternatively, as I said, you could use an array of BOOL.

Answer 2

Create a property that hold the selected index:
#property (nonatomic, assign) NSInteger selectedIndex;
Then:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
if (self.selectedIndex == indexPath.row) {
self.selectedIndex = -1;
} else {
self.selectedIndex = indexPath.row;
}
[tableView reloadData];
}
And present the checkmark:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
// do usual stuff here including getting the cell
if (indexPath.row == self.selectedIndex) {
cell.accessoryType = UITableViewCellAccessoryCheckmark;
} else {
cell.accessoryType = UITableViewCellAccessoryNone;
}
return cell;
}

Answer 3

There are a couple ways you can support a checkmark on a table cell. This example code seems to be assuming that you only have one checked cell in your table view, and tapping a different cell would move the checkmark to that other cell.
Basically, checkedData would be a property on your class (typically you would be using a subclass of UITableViewController, but it doesn't need to be, as long as your class conforms to both UITableViewDataSource and UITableViewDelegate). The data variable is derived from the selected row.
Here's one way you could fill in the gaps:
YourClass.h
// ...
#property int checkedIndex;
// ...
YourClass.m
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// do usual stuff here including getting the cell
// See if this row is the checked row
int thisRowIndex = indexPath.row;
if (thisRowIndex == self.checkedIndex)
{
cell.accessoryType = UITableViewCellAccessoryCheckmark;
} else {
cell.accessoryType = UITableViewCellAccessoryNone;
}
return cell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// determine the selected data from the IndexPath.row
int thisRowIndex = indexPath.row;
if (thisRowIndex != self.checkedData) {
self.checkedIndex = thisRowIndex;
}
[tableView reloadData];
}
Of course, this doesn't really solve your problem. Since you want the cell to toggle, you will need to keep a record of which cells are on and which are off. If you're only toggling one or two cells, you could get away with having one or two BOOL properties on your class which represent the state of each cell. If you have a larger number of cells that you want to toggle, you should store the state of each cell in an NSMutableArray, and get/set the values that match up with each index.
YourClass.h
// ...
{
NSMutableArray *_checkedRows; // This is an instance variable, not a property.
}
// ...
YourClass.m
// ================================================================
// Don't forget to initialize _checkedRows in your [init] method!!!
// ================================================================
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// do usual stuff here including getting the cell
// See if this row is the checked row
BOOL rowIsChecked = [[_checkedRows objectAtIndex:indexPath.row] boolValue];
if (rowIsChecked)
{
cell.accessoryType = UITableViewCellAccessoryCheckmark;
} else {
cell.accessoryType = UITableViewCellAccessoryNone;
}
return cell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
// determine the selected data from the IndexPath.row
// Set the state of the cell to the opposite of what it currently is.
BOOL rowIsChecked = [[_checkedRows objectAtIndex:indexPath.row] boolValue];
[_checkedRows replaceObjectAtIndex:indexPath.row
withObject:[NSNumber numberWithBool:!rowIsChecked]];
[tableView reloadData];
}