iOS UITableView sections with fetchedResultsController confusion - ios

Question

I have an entity being displayed in a table view in just one section. The entity has two attributes, workoutName and trainingLevel. Both are of string type. Training level consists of the 3 types: 1, 2, 3. (trainingLevel = (Integer 16 or String Type? Which would be ideal?) I would like to split the table into three sections, each section containing entries for the corresponding training level.
How do I do this? The code I am currently using is below:
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return self.workoutType.workouts.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell =
[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:CellIdentifier];
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
}
WorkoutSet *workoutSet = [self.fetchedResultsController objectAtIndexPath:indexPath];
cell.textLabel.text = workoutSet.workoutName;
cell.detailTextLabel.text = [NSString stringWithFormat:#"(%d)", workoutSet.days.count];
}
-(void)fetchWorkoutSets
{
NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:#"WorkoutSet"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"workoutType = %#", self.workoutType];
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:#"workoutName" ascending:YES];
[fetchRequest setSortDescriptors:#[sortDescriptor]];
[fetchRequest setPredicate:predicate];
self.fetchedResultsController = [[NSFetchedResultsController alloc]
initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext
sectionNameKeyPath:nil cacheName:nil];
NSError *error;
if (![self.fetchedResultsController performFetch:&error])
{
NSLog(#"Fetch failed: %#", error);
}
}
What I am struggling with is:
How to determine the number of rows for each section through the core data model by fetching number of entries with training level 1 or 2 or 3.
How to fill the rows of each section by fetching the correct items.
How to give a title to each section header.

Answer 1

Here is a good tutorial on using fetchedResultsControllers: http://www.raywenderlich.com/999/core-data-tutorial-for-ios-how-to-use-nsfetchedresultscontroller
Create some properties to hold your context and fetches:
#property (nonatomic,strong)NSManagedObjectContext* managedObjectContext;
#property (nonatomic,retain)NSFetchedResultsController *fetchedResultsController;
In your fetchedResultsController property, use sectionKeyNamePath to set up your fetched results in sections:
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:#"Workouts"
inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSSortDescriptor *sort = [[NSSortDescriptor alloc]
initWithKey:#"workoutName" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];
[fetchRequest setFetchBatchSize:20];
NSFetchedResultsController *theFetchedResultsController =
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:managedObjectContext
sectionNameKeyPath:#"trainingLevel"
cacheName:#"Root"];
self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;
return _fetchedResultsController;
}
Your initial population of your fetchedResultsController can happen in your -viewDidLoad:
- (void)viewDidLoad {
[super viewDidLoad];
NSError *error;
if (![[self fetchedResultsController] performFetch:&error]) {
// Update to handle the error appropriately.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1); // Fail
}
}
You'd then return the number of sections and number of rows in sections like this:
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return [[self.fetchedResultsController sections] count];
}
- (NSInteger)tableView:(UITableView *)tableView
numberOfRowsInSection:(NSInteger)section
{
id <NSFetchedResultsSectionInfo> sectionInfo =
[[[self fetchedResultsController] sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
}
You can then get your managed object for the particular row like this:
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// init the cell
// and whatever other setup needed
WorkoutSet *workoutSet =
[self.fetchedResultsController objectAtIndexPath:indexPath];
// configure the cell from the managedObject properties
}