在分段 UITableView 中存储多个选择

Question

I have a list of people in a UITableView, sectioned by the first letter of the persons name.

I want this list to allow MULTIPLE selections (imagine 100 people, in a list, sectioned by name, with a check box next to each name).

No problem with the UI - all sorted.

Its how to STORE the selections?

I need way to store and retrieve the selections (simple BOOL values) from some sort of array, by using the indexPath to find them.

Before using sections, it was easy - just an NSMutableArray, and retrieve by indexPath.row. But with sections I have to find by BOTH section AND row. Multidimensional arrays don't seem to go well with Objective C, though a multidimensional c array was suggested in one post somewhere.

I could save to the database - but thats a lot of save and retrieves as you scroll up and down a table checking and unchecking tickboxes.... and I dont need the data to persist in the DB anyway - going to then create records with pointers to the selected records.

Surely I am not the first person to reach this dilemma.

Any ideas?

Answer 1

I'd still be interested to hear ideas - but after trawling the interwebs for hours (until 3am,) and not coming up with a solution, I decided to use an NSDictionary: constructing the key from the indexPath row and section thus:

 - (void) setSelected:(NSMutableDictionary*)dict forIndexPath:(NSIndexPath*)indexPath withValue:(BOOL)selected{

            NSString *cellIdentifier = [NSString stringWithFormat:@"Cell-%i-%i", (int)indexPath.section, (int)indexPath.row];

            [dict setObject:[NSNumber numberWithBool:selected] forKey:cellIdentifier];

 }

- (BOOL) getSelected:(NSMutableDictionary*)dict forIndexPath:(NSIndexPath*)indexPath {

    NSString *cellIdentifier = [NSString stringWithFormat:@"Cell-%i-%i", (int)indexPath.section, (int)indexPath.row];
    BOOL selected=[[dict objectForKey:cellIdentifier]  boolValue];

    return selected;

}
- (BOOL) toggleSelected:(NSMutableDictionary*)dict forIndexPath:(NSIndexPath*)indexPath {

    NSString *cellIdentifier = [NSString stringWithFormat:@"Cell-%i-%i", (int)indexPath.section, (int)indexPath.row];

    BOOL selected=[[dict objectForKey:cellIdentifier]  boolValue];
    selected=!selected;

    [self setSelected:dict forIndexPath:indexPath withValue:selected];

    return selected;
}

Answer 2

You could use a mutable array to store persons or indexes of persons that are selected. This will go inside your didSelectRowAtIndexPath

UITableViewCell *currentCell = [self.tableView cellForRowAtIndexPath:indexPath];
if (currentCell.accessoryType == UITableViewCellAccessoryNone) {
    currentCell.accessoryType = UITableViewCellAccessoryCheckmark;
    //save/delete your person or index in/from a global mutable array
}

And in your cellForRowATIndexPath you could set the accessory based on whats in the array and whats not. Hope it helps:)