Question

I have a Mutable Dictionary which allows people to choose a selection of days of the week. Once a day has been selected the state is updated using numberWithBool.

When I NSLog the output it looks something like this:

    {
    day = Monday;
    isSelected = 1;
},
    {
    day = Tuesday;
    isSelected = 0;
},
    {
    day = Wednesday;
    isSelected = 0;
},
    {
    day = Thursday;
    isSelected = 0;
},
    {
    day = Friday;
    isSelected = 0;
},
    {
    day = Saturday;
    isSelected = 0;
},
    {
    day = Sunday;
    isSelected = 1;
}

I would like to be able to extract the chosen days and produce the output in the form of a string. So in this example the output would be: Monday, Sunday

How can I do this?

My code for creating the dictionary is below:

NSMutableArray * tempSource = [[NSMutableArray alloc] init];
NSArray *daysOfWeek = [NSArray arrayWithObjects:@"Monday", @"Tuesday", @"Wednesday", @"Thursday", @"Friday", @"Saturday", @"Sunday",nil];
for (int i = 0; i < 7; i++)
{
    NSString *dayOfWeek = [daysOfWeek objectAtIndex:i];
    NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithObjectsAndKeys:dayOfWeek, @"day",   [NSNumber numberWithBool:NO], @"isSelected",nil];
    [tempSource addObject:dict];
}

[self setSourceArray:tempSource];
[tempSource release];

Answer 1

You can loop thru all of your items in the array and build a side-array only containing names of the day (1), or you can use a predicate and then KVC to extract the days directly (2).

Then join the components of the filtered array into a string.

Solution 1:

NSMutableArray selectedDays = [[NSMutableArray alloc] init];
for(NSDictionary* entry in sourceArray)
{
    if (([entry objectForKey:@"isSelected"] boolValue]) {
        [selectedDays addObject:[entry objectForKey:@"day"]];
    }
}
NSString days = [selectedDays componentsJoinedByString:@", "];
[selectedDays release];

Solution 2:

NSPredicate* filter = [NSPredicate predicateWithFormat:@"SELF.isSelected == 1"]; // not sure about the exact format (no mac here to test right now so you may adapt a bit if it does not work directly)
// get the array of dictionaries but only the ones that have isSelected==1
NSArray selectedEntries = [sourceArray filteredArrayUsingPredicate:filter]; 
NSArray selectedDays = [selectedEntries valueForKey:@"day"]; // extract the "days" keys of the dictionaries. We have a NSArray of strings then.
NSString days = [selectedDays componentsJoinedByString:@", "];

---

As a side note, your way of doing this is quite strange. Why having an NSArray of NSDictionaries for this? As this is simple and a static-size array containing only BOOL, you may instead for this particular case simply use C array BOOL selected[7] and nothing more.

Then to have the name of the weekdays you should instead use the methods of NSCalendar/NSDateFormatter/NSDateComponents to get the standard names of the weekdays (automatically in the right language/locale of the user): create an NSDate using a NSDateComponent for which you simply define the weekday component, then use an NSDateFormatter to convert this to a string, choosing a string format that only display the weekday name.

---

-(void)tableView:(UITableView*)tv didSelectRowAtIndexPath:(NSIndexPath*)indexPath {
  // selectedDays is an instance variable in .h declared as
  // BOOL selectedDays[7];
  selectedDays[indexPath.row] = ! selectedDays[indexPath.row];
  [tv reloadData];
}

-(UITableViewCell*)tableView:(UITableView*)tv cellForRowAtIndexPath:(NSIndexPath*)indexPath {
  static NSString* kCellIdentifier = @"DayCell";
  UITableViewCell* cell = [tv dequeueReusableCellWithIdentifier:kCellIdentifier];
  if (!cell) {
    cell = [[[UITableViewCell alloc] initWithStyle:... identifier:kCellIdentifier]; autorelease];
    // configure here every property that is common to all for your cells (text color, etc)
  }

  // configure here things that will change from cell to cell
  cell.accessoryType = selectedDays[indexPath.row] ? UITableViewCellAccessoryTypeCheckmarck : UITableViewCellAccessoryTypeNone;
  cell.textLabel.text = weekdayName(indexPath.row);

  return cell;
}

// Simple C function to return the name of a given weekday
NSString* weekdayName(int weekday)
{
#if WAY_1
  /**** Solution 1 ****/
  // Optimization note: You may compute this once for all instead of recomputing it each time
  NSDateComponents* comp = [[[NSDateComponents alloc] init] autorelease];
  [comp setWeekday:weekday+1]; // weekdays start at 1 for NSDateComponents
  NSDate* d = [[NSCalendar currentCalendar] dateFromComponents:comp];

  NSDateFormatter* df = [[[NSDateFormatter alloc] init] autorelease];
  [df setDateFormat:@"EEEE"]; // format for the weekday
  return [[df stringFromDate:d] capitalizedString];
#else
  /**** Solution 2 ****/
  NSDateFormatter* df = [[[NSDateFormatter alloc] init] autorelease];
  NSArray* weekdayNames = [df weekdaySymbols]; // or maybe one of its sibling methods? check what is returned here to be sure
  return [weekdayNames objectAtIndex:weekday];
#endif
}