Ins and Outs of Deleting Data

#import "EntryListTableViewController.h"
#import "CoreDataStack.h"
#import "DiaryEntry.h"


@interface EntryListTableViewController () <NSFetchedResultsControllerDelegate>
@property (nonatomic, strong) NSFetchedResultsController *fetchedResultsController;

@end

@implementation EntryListTableViewController


-(NSFetchRequest *)entryListfetchRequest
{
    //this method can be tested independently of actually fetching data.
    NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"DiaryEntry"];

    fetchRequest.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"date" ascending:NO]];

    return fetchRequest;
}

-(NSFetchedResultsController *)fetchedResultsController
{
    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;

    }
    //grab the core data stack
    CoreDataStack *coreDataStack = [CoreDataStack defaultStack];

    //create a fetch request that calls the entryListRequest method.
    NSFetchRequest *fetchRequest = [self entryListfetchRequest];


    _fetchedResultsController = [[NSFetchedResultsController alloc]initWithFetchRequest:fetchRequest managedObjectContext:coreDataStack.managedObjectContext sectionNameKeyPath:@"sectionName" cacheName:nil];
    _fetchedResultsController.delegate = self;

    return _fetchedResultsController;

};


-(NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
    //grab the section info from our fetched results controller.

    id <NSFetchedResultsSectionInfo> sectionInfo = [self.fetchedResultsController sections][section];

    return [sectionInfo name];
}


- (id)initWithStyle:(UITableViewStyle)style
{

    self = [super initWithStyle:UITableViewStyleGrouped];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;


    [self.fetchedResultsController performFetch:nil];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{

    // Return the number of sections.
    return self.fetchedResultsController.sections.count;
}



#pragma mark Number of rows in section.

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{

    // Return the number of rows in the section.
    id <NSFetchedResultsSectionInfo> sectionInfo = [self.fetchedResultsController sections][section];

    return [sectionInfo numberOfObjects];
}

#pragma mark Cell For row at indexPath
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"Cell" forIndexPath:indexPath];

    // Configure the cell...

    DiaryEntry *entry = [self.fetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = entry.body;

    return cell;
}



#pragma mark tableViewCell Editing style
-(UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath
{
    //this i one of the methods required to swipe to delete.
    return UITableViewCellEditingStyleDelete;

}

-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    //to delete an entry we first have to get the item we want to delete, in this case its the diary entry.
    DiaryEntry *entry = [self.fetchedResultsController objectAtIndexPath:indexPath];
    CoreDataStack *coreDataStack = [CoreDataStack defaultStack];
    //select our coreDataStack and delete the entry from the stack.
    [[coreDataStack managedObjectContext]deleteObject:entry];
    [coreDataStack saveContext];
}

//if the content has been changed save it and reload the data in the table view.
-(void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{

    [self.tableView beginUpdates];

}

-(void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath
{
    //this method is called whenever a row is inserted, removed, updated, moved, or changed.


    //we're going to switch on the type to actually determined what's happening.
    switch (type) {
            //if the type is NSFetchedResultsChangeInsert we will insert a new row at the new indexPath.

        case NSFetchedResultsChangeInsert:
            [self.tableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
            break;
             //if the type is NSFetchedResultsChangeDelete we will remove a row at the indexPath.
        case NSFetchedResultsChangeDelete:
            [self.tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
            break;
            //if the type is NSFetchedResultsChangeUpdate we will reload a row at the current indexPath.
        case NSFetchedResultsChangeUpdate:
            [self.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
            break;
    }


}

-(void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
   [self.tableView endUpdates];
   // [self.tableView reloadData];

}