Core data, count and group by - objective-c

Question

I have an entity with 2 attributes, an NSDate and a boolean value. (this is going to be a large "table")
I need to count all YES and NO values for the boolean between two dates, grouped by days. How can i do this?
The result I'm looking for is
{
totalYes = 10,
totalNo = 5,
date = dd-mm-yyyy
},
{
totalYes = 15,
totalNo = 3,
date = dd-mm-yyyy
},
etc
Thanks

Answer 1

You can try this approach:
1)Get all the enteties with YES,sorted by date
2)Go trough this array and fill array with dictionaries with day value and number of yeses
3)Then, do the ame thing with noe's,adding number of no to that array of dictionaries.
NSFetchRequest *request = [[NSFetchRequest alloc]init];
request.entity = [NSEntityDescription entityForName:#"Day" inManagedObjectContext:context];
request.predicate = [NSPredicate predicateWithFormat:#"yesorno = %#",YES];
NSError *error = nil;
request.sortDescriptors =[NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:#"date" ascending:YES]];
//Here you get all the enteties with YES,sorted by date
NSArray *days = [context executeFetchRequest:request error:&error];
NSMutableArray *arrayOfDates = [NSMutableArray array];
int firstDay = [[[NSCalendar currentCalendar]components:NSDayCalendarUnit fromDate:[[days objectAtIndex:0]date]]day];
//Add the first day dictionary
[arrayOfDates addObject:[NSMutableDictionary dictionaryWithObjectsAndKeys:[[days objectAtIndex:0]date],#"Day", nil];
int numberOfYes = 0;
int dayNumber = 0;
for(NSManagedObject *day in days)
{
if( [[[NSCalendar currentCalendar]components:NSDayCalendarUnit fromDate:[day date]]day]>firstDay)
{
//save number of yeses for the previous day,because we are done with it
[[arrayOfDates objectAtIndex:dayNumber]setValue:[NSNumber numberWithInt:numberOfYes] forKey:#"NumberOfYes"];
numberOfYes = 1;
dayNumber++;
firstDay = [[[NSCalendar currentCalendar]components:NSDayCalendarUnit fromDate:[day date]]day];//date with new day
[arrayOfDates addObject:[NSMutableDictionary dictionaryWithObjectsAndKeys:[day date],#"Day", nil];//Add this day dictionary to array
}else
{
numberOfYes++;
}
}
//And somrthing similar to No