Split nsarray into sections by NSDate - ios

Question

I have an NSArray that is extracted from core data. The entities in the array have a date attribute (of type NSDate ofcourse). What I want to do is this:
The array needs to be displayed in a table view,
the sections, and their titles are months , of the objects in the array
For example if I have 3 objects (april 1, april 3 & july 7) there should be 2 sections:
- april 2012(2 obj)
- july 2012 (1 obj)).
How do I split the array like this?

Answer 1

Try using a NSFetchedResultsController and a custom sectionNameKeyPath which should be a method in your NSManagedObject subclass.
The fetchedResultsController can be set up as following:
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:#"MyObject"];
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:#"date" ascending:YES];
request.sortDescriptors = #[sortDescriptor];
NSFetchedResultsController *frc = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:managedObjectContext sectionNameKeyPath:#"monthAsString" cacheName:nil];
You need to implement the monthAsString method in your managedObject subclass. Allocate the NSDateFormatter only once, because it won't perform well if you allocate a new instance for every call.
- (NSString *)monthAsString {
static NSDateFormatter *formatter;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
formatter = [[NSDateFormatter alloc] init];
formatter.dateFormat = #"MMMM yyyy";
});
NSString *dateString = [formatter stringFromDate:self.date];
return dateString;
}