I have a column in core data that stores a date (eg:2006-01-26). I used an array to store all the years by using NSDateComponents on these stored dates.(e.g.: on above date if i use NSDateComponents, I get 2006 as a year). These years are NSNumbers, and using them in my predicate I want to fetch the column which is NSDate with all Date components. And fetched records should be only of particular year. I am now confused about how I could match a year components with one of those in array, and create predicate.
- (void)viewDidLoad
{
[super viewDidLoad];
NSFetchRequest *request = [[NSFetchRequest alloc]init];
NSError *error;
//AppDelegate *app = [[UIApplication sharedApplication]delegate];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Movies" inManagedObjectContext:self.managedObjectContxt];
[request setEntity:entity];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc]
initWithKey:@"releaseDate" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor,nil];
[request setSortDescriptors:sortDescriptors];
//[request setReturnsDistinctResults:YES ];
// [request setEntity:entity];
[sortDescriptors release];
[sortDescriptor release];
[request setPropertiesToFetch:[NSArray arrayWithObject:@"releaseDate"]];
NSMutableArray *arrOfdMovies = [[self.managedObjectContxt executeFetchRequest:request error:&error]mutableCopy];
[self setArrOfFetchdMovies:arrOfdMovies];
arrOfDistinctYr = [[NSMutableArray alloc]init];
NSMutableArray *temp = [[NSMutableArray alloc]init];
for (int i = 0; i<[arrOfdMovies count]; i++) {
// NSLog(@"%@",[[arrOfdMovies objectAtIndex:i] valueForKey:@"releaseDate"]);
//date to its components
NSDate *now = [[arrOfdMovies objectAtIndex:i]valueForKey:@"releaseDate"];
// Specify which units we would like to use
unsigned units = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit;
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *component_s = [calendar components:units fromDate:now];
NSInteger year = [component_s year];
NSLog(@"%i", year);
// NSInteger month = [components month];
// NSInteger day = [components day];
NSNumber *num= [NSNumber numberWithInteger:year];
[temp addObject:num];
}
[self setArrOfDistinctYr:temp];
//distinct value logic.
NSSet *uniqueYrs = [NSSet setWithArray:arrOfDistinctYr];
arr = [[NSArray alloc]initWithArray:[uniqueYrs allObjects]];
//sorting
NSArray *ar = [arr sortedArrayUsingSelector:@selector(compare:)];
self.arr = ar;
[self.managedObjectContxt retain];
[request release];
}
the array "ar" contains only years in distinct and sorted manner. But data types of this array elements are "NSNumbr" Now How can i form a predicate which will make use of this array to display records for the particular year(how to check year from date field of core data [which has date say- 2006-01-26]). I tried in following way -
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// return 2;
NSFetchRequest *requst=[[NSFetchRequest alloc]init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Movies" inManagedObjectContext:self.managedObjectContxt];
[requst setEntity:entity];
requst.predicate = [NSPredicate predicateWithFormat:@"releaseDate CONTAINS%@", [arr objectAtIndex:section]];
NSError *error = nil;
NSMutableArray *array = [[self.managedObjectContxt executeFetchRequest:requst error:&error]mutableCopy];
[requst release];
return [array count];
}
Once i get this, i can display records n my viewController.
One of the way is - Knowing the year, you could get start of the year 2006-01-01 and end of the year 2006-12-31. And then filter for dates that are between them.
For creating predicates - Have a look at Predicate Guide
It has few good example, including some dealing with NSDate predicates.