I have a method that I use to hold and move cells in my table view to different index that looks like this:
- (void)moveTableView:(FMMoveTableView *)tableView moveRowFromIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
NSArray *allObjects = [self.fetchedResultController fetchedObjects];
//array to hold the new order
NSMutableArray * arrayCorectOrder = [NSMutableArray new];
//the target object that is in the index we are moving from
Target *target = [self.fetchedResultController objectAtIndexPath:fromIndexPath];
}
i have a coreDataStack class that takes care of all the core data stuff (creating a singelton), it looks like this:
#import "CoreDataStack.h"
@implementation CoreDataStack
#pragma mark - Core Data stack
@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
+ (instancetype)defaultStack {
static CoreDataStack *defaultStack;
static dispatch_once_t onceTocken;
dispatch_once (&onceTocken, ^{
defaultStack = [[self alloc] init];
});
return defaultStack;
}
- (NSURL *)applicationDocumentsDirectory {
// The directory the application uses to store the Core Data store file. This code uses a directory named "digitalCrown.Lister" in the application's documents directory.
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
- (NSManagedObjectModel *)managedObjectModel {
// The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
if (_managedObjectModel != nil) {
return _managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"Lister" withExtension:@"momd"];
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return _managedObjectModel;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it.
if (_persistentStoreCoordinator != nil) {
return _persistentStoreCoordinator;
}
// Create the coordinator and store
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Lister.sqlite"];
NSError *error = nil;
NSString *failureReason = @"There was an error creating or loading the application's saved data.";
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
// Report any error we got.
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
dict[NSLocalizedDescriptionKey] = @"Failed to initialize the application's saved data";
dict[NSLocalizedFailureReasonErrorKey] = failureReason;
dict[NSUnderlyingErrorKey] = error;
error = [NSError errorWithDomain:@"YOUR_ERROR_DOMAIN" code:9999 userInfo:dict];
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return _persistentStoreCoordinator;
}
- (NSManagedObjectContext *)managedObjectContext {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.)
if (_managedObjectContext != nil) {
return _managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (!coordinator) {
return nil;
}
_managedObjectContext = [[NSManagedObjectContext alloc] init];
[_managedObjectContext setPersistentStoreCoordinator:coordinator];
return _managedObjectContext;
}
#pragma mark - Core Data Saving support
- (void)saveContext {
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil) {
NSError *error = nil;
if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
}
}
@end
and whenever i add new object to core data i do it this way:
- (void)insertTeget {
CoreDataStack *stack = [CoreDataStack defaultStack];
Target *target = [NSEntityDescription insertNewObjectForEntityForName:@"Target" inManagedObjectContext:stack.managedObjectContext];
if (self.myTextView.text != nil) {
target.body = self.myTextView.text;
target.time = [NSDate date];
}
[stack saveContext];
}
in the table view when I'm fetching the data i do it this way:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *cellIdentifier = @"StackTableViewCell";
Target *target = [self.fetchedResultController objectAtIndexPath:indexPath];
StackTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (!cell)
{
NSArray *topLevelObjects = [[NSBundle mainBundle] loadNibNamed:@"StackTableViewCell" owner:self options:nil];
cell = [topLevelObjects objectAtIndex:0];
}
cell.cellLabel.text = target.body;
cell.cellLabel.font = [UIFont fontWithName:@"Candara-Bold" size:20];
cell.showsReorderControl = YES;
// Configure the cell...
return cell;
}
this is my fetchresultconroller/fetch request config in the table view controller class:
- (NSFetchRequest *)targetsFetchRequest {
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Target"];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"time" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
return fetchRequest;
}
- (NSFetchedResultsController *)fetchedResultController {
if (_fetchedResultController != nil) {
return _fetchedResultController;
}
CoreDataStack *stack = [CoreDataStack defaultStack];
NSFetchRequest *fetchRequest = [self targetsFetchRequest];
_fetchedResultController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:stack.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
_fetchedResultController.delegate = self;
return _fetchedResultController;
}
and now I wand to check if the order was changed so I need to change the order in the database...
how do I do this?
thanks!
As per my comments, the fetched results controller bases the indexPath for each object on the sort order of the underlying fetch - in your case time. If you want the user to be able to override this, and reorder the rows, then change the FRC to use a different sort order. Add a new attribute (of date type) to your entity, named sortTime, and amend the targetsFetchRequest method to use sortTime as the sort key.
Whenever you add a new Target, set the sortTime at the same time. When it comes to reordering the rows, set the value of sortTime to ensure that the FRC places the Target at the new indexPath. Something like this:
-(void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath {
Target *targetToMove = [self.fetchedResultsController objectAtIndexPath:sourceIndexPath];
if (destinationIndexPath.row == 0) {
// to move to row 0, the new sortTime can be any value
// that is less than the sortTime of the Target currently at
// row 0
Target *targetAtRow0 = [self.fetchedResultsController objectAtIndexPath:destinationIndexPath];
targetToMove.sortTime = [targetAtRow0.sortTime dateByAddingTimeInterval:-1];
} else {
// for any other row, set the sortTime to be half way
// between the sortTime for the row before the new position
// and the sortTime for the row at the new position
Target *targetBefore = [self.fetchedResultsController objectAtIndexPath:[NSIndexPath indexPathForRow:(destinationIndexPath.row-1) inSection:destinationIndexPath.section]];
Target *targetAfter = [self.fetchedResultsController objectAtIndexPath:destinationIndexPath];
double lowerTimeInterval = [targetBefore.sortTime timeIntervalSinceReferenceDate];
double upperTimeInterval = [targetAfter.sortTime timeIntervalSinceReferenceDate];
double newInterval = (lowerTimeInterval + upperTimeInterval)/2;
NSDate *newSortTime = [NSDate dateWithTimeIntervalSinceReferenceDate:newInterval];
targetToMove.sortTime = newSortTime;
}
NSError *error;
if (![self.managedObjectContext save:&error]) {
NSLog(@"SaveContext: error %@, %@", error, [error userInfo]);
abort();
}
}
This should trigger your FRC delegate methods to perform the necessary table view updates.