
4. CoreData for other non-health stats
You made it to the end! Ok, so we are basically going to be adding another store to our app and reading and writing data to THAT store as well.
First let’s add a new tab and make it a UITableViewController as well. It will have dynamically populated cells.

Now embed it!

Your final storyboard should look like this:

Add a new Swift class called Swimming Data and set that new UITableViewController scene to its class. Make that class file look like this:
import Foundation import UIKit class SwimmingData: UITableViewController { }
Now we must add CoreData. To do this we need to create a CoreData stack and a xcdatamodeld file. First thing is first, let’s add the xcdatamodeld file by New->File->CoreData->DataModel. Name it SwimModel. Create an entity called Swim and add the following attributes:
- pace : Int16
- date : Date
- laps : Int16
- meters : Double
- totalTime : Double
Now with the xcdatamodeld file selected, go to Editor and select Create NSManagedObject subclass:

Make sure SwimModel is selected, click Next, make sure to select the Swim entity, click Next and you should get a Swim.swift class like this:
import Foundation import CoreData class Swim: NSManagedObject { @NSManaged var date: NSDate @NSManaged var laps: NSNumber @NSManaged var totalTime: NSNumber @NSManaged var meters: NSNumber @NSManaged var pace: NSNumber }
Perfect! All you need now is your stack! To do this, again create a New->File->Source->Swift File-> and name it CoreDataStack. Now replace everything in there with this:
import CoreData class CoreDataStack { let context:NSManagedObjectContext let psc:NSPersistentStoreCoordinator let model:NSManagedObjectModel let store:NSPersistentStore? init() { //1 let bundle = NSBundle.mainBundle() let modelURL = bundle.URLForResource("SwimModel", withExtension:"momd") model = NSManagedObjectModel(contentsOfURL: modelURL!)! //2 psc = NSPersistentStoreCoordinator(managedObjectModel:model) //3 context = NSManagedObjectContext() context.persistentStoreCoordinator = psc //4 let documentsURL = applicationDocumentsDirectory() let storeURL = documentsURL.URLByAppendingPathComponent("SwimFit4") let options = [NSMigratePersistentStoresAutomaticallyOption: true] var error: NSError? = nil store = psc.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: storeURL, options: options, error:&error) if store == nil { println("Error adding persistent store: \(error)") abort() } } func saveContext() { var error: NSError? = nil if context.hasChanges && !context.save(&error) { println("Could not save: \(error), \(error?.userInfo)") } } func applicationDocumentsDirectory() -> NSURL { let fileManager = NSFileManager.defaultManager() let urls = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask) as [NSURL] return urls[0] } }
Now since this is not a CoreData tutorial, I will not go into the details, but every CoreData project needs a MOM, MOC and PSC. That is what we initialize here.
Now we can begin writing to our MOC and PSC. To test run it, let’s hardcode a value. Go to the SwimmingData Class and first give it an import CoreData at the top. Now declare a property for your stack inside your class of course:
lazy var coreDataStack = CoreDataStack() var workouts = NSMutableArray()
We are creating a CoreDataStack instance and we are creating a mutable array.
Then give it a viewDidLoad method like this:
override func viewDidLoad() { super.viewDidLoad() //Create Sample Swim object var description = NSEntityDescription.entityForName("Swim", inManagedObjectContext:coreDataStack.context) var sampleSwim = Swim(entity:description!, insertIntoManagedObjectContext:coreDataStack.context) sampleSwim.laps = 24 sampleSwim.meters = 50 sampleSwim.totalTime = 40 sampleSwim.pace = 6 sampleSwim.date = NSDate() coreDataStack.saveContext() //Add object to array self.workouts.addObject(sampleSwim) //Refresh UI self.tableView.reloadData() }
Now add an identifier for the cell like so:
let JournalViewControllerTableViewCellReuseIdentifier: NSString = "Cell"
as a property at the top of the class.
So of course don’t forget to set the identifier in your storyboard scene. Finally, implement both datasource methods:
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return self.workouts.count } override func tableView(tableView: UITableView?, cellForRowAtIndexPath indexPath: NSIndexPath?) -> UITableViewCell { let cell: UITableViewCell = self.tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath:indexPath!) as UITableViewCell var myWorkout: Swim = self.workouts[indexPath!.row] as Swim let dateFormatter = NSDateFormatter() dateFormatter.dateFormat = "yyyy'-'MM'-'dd HH':'mm':'ss" let date = dateFormatter.stringFromDate(myWorkout.date as NSDate) println(date) cell.textLabel.text = date cell.detailTextLabel!.text = myWorkout.totalTime.stringValue return cell; }
And don’t forget to set your cell type to Right Detail in your storyboard. If you Build & Run and switch to the newly created tab, you might get a crash saying:
Unable to load class Swim …
This is because you need to fully qualify the class name in CoreData, so select your xcdatamodeld file and with your Swim entity selected, make sure to append the Class name in the inspector on the right like so:

Basically you need to ensure that you append your project name to the Class name field.
Now run your app and go over to the Workouts tab and see your hardcoded workout in the tableview.
Before we move on, let’s take a few minutes to work on some details. While this provides the info required by the user, it would be nice to polish it up a bit. First, we should add the letters “mins” to the totalTime displayed in the cell. Second, it would be nice to format the date a little more such that its more human readable. So go back to your cellForRowAtIndexPath and make the following changes:
override func tableView(tableView: UITableView?, cellForRowAtIndexPath indexPath: NSIndexPath?) -> UITableViewCell { let cell: UITableViewCell = self.tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath:indexPath!) as UITableViewCell var myWorkout: Swim = self.workouts[indexPath!.row] as Swim var formatString = NSDateFormatter.dateFormatFromTemplate("EdMMM", options: 0, locale: NSLocale.currentLocale()) let dateFormatter = NSDateFormatter() dateFormatter.dateFormat = formatString let date = dateFormatter.stringFromDate(myWorkout.date as NSDate) println(date) cell.textLabel.text = date cell.detailTextLabel!.text = myWorkout.totalTime.stringValue + " mins" return cell; }
There, now the user has a little mode detailed info of the data displayed. We could go on and modify the cell to hold more data or even be selectable such that it would segue into a detail view controller to display all the info.
WRITING TO CORE DATA
Now all that is left to do is actually, remove that viewDidLoad code that writes to CoreData and instead, write to CoreData from our Workout view controller. So back in WorkoutViewController, first import CoreData at the top, then add this property:
lazy var coreDataStack = CoreDataStack()
and finally, in the saveMyWorkout method, after we calculate our joules burned, or before, it doesn’t matter, add this code:
//E - Perhaps just store laps and meters per lap = total metes in some extra field within the SwimFit app to display it. var description = NSEntityDescription.entityForName("Swim", inManagedObjectContext:coreDataStack.context) var sampleSwim = Swim(entity:description!, insertIntoManagedObjectContext:coreDataStack.context) var numberFormatter = NSNumberFormatter() var nolaps:NSNumber? = numberFormatter.numberFromString(numberOfLapsValue!) if let nolaps = nolaps { sampleSwim.laps = Int(nolaps) } var nometers:NSNumber? = numberFormatter.numberFromString(metersPerLapValue!) if let nometers = nometers { sampleSwim.meters = Double(nometers) } var totime:NSNumber? = numberFormatter.numberFromString(workoutDurationValue!) if let totime = totime { sampleSwim.meters = Double(totime) } sampleSwim.pace = pace sampleSwim.date = NSDate() coreDataStack.saveContext()
This will save that other data, which is not HealthKit or health store data, into CoreData for later use. Now let’s just go modify our SwimmingData view controller to make it fetch.
You already added a CoreDataStack variable to your SwimmingData view controller, so just add a fetchRequest var like this, right below the CoreDataStack var:
var coreDataStack: CoreDataStack! var fetchRequest: NSFetchRequest!
Now in viewDidLoad add this neat code:
fetchRequest = coreDataStack.model.fetchRequestTemplateForName("FetchRequest")
This is a stored fetch request and to use it you must head over to the xcdatamodeld.file and create a new FetchRequest, leave its name as FetchRequest and now from the editor leave Swim as the selected entity to fetch from. Now go back to SwimmingData and add this method:
//MARK - Helper methods func fetchAndReload(){ var error: NSError? let results = coreDataStack.context.executeFetchRequest(fetchRequest, error: &error) as [Swim]? if let fetchedResults = results { workouts = fetchedResults.copy() as NSMutableArray } else { println("Could not fetch \(error), \(error!.userInfo)") } tableView.reloadData() }
And now call this method from viewDidLoad. This will load your fetched data from CoreData into your tableview.
This will fetch the items in the order they were inserted, but you can also add a sort descriptor.
Add this lazy property at the top of your SwimmingData class:
lazy var dateSortDescriptor: NSSortDescriptor = { var sd = NSSortDescriptor(key: "Swim.laps", ascending: true) return sd }()
Then in the viewDidLoad add this as a property of your fetchRequest:
fetchRequest.sortDescriptors =[dateSortDescriptors]
NSFETCHEDRESULTSCONTROLLER OPTION
Alternatively you can also use NSFetchedResultsController. NSFRC is a neat object that is created specifically for fetching and manipulating data from a CoreData query. Its special in many respects but mainly because it works nicely with table views. It can store information about table structure and can allow for interaction between its data and the tableview at the same time. So add this property to the top of your class:
var fetchedResultsController : NSFetchedResultsController!
In your viewDidLoad:
//1 let fetchRequest = NSFetchRequest(entityName: "Swim") let sortDescriptor = NSSortDescriptor(key: "totalTime", ascending: false) fetchRequest.sortDescriptors = [sortDescriptor] //2 fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: coreDataStack.context, sectionNameKeyPath: nil, cacheName: nil) //3 var error: NSError? = nil if (!fetchedResultsController.performFetch(&error)) { println("Error: \(error?.localizedDescription)") }
Now replace your datasource methods with:
func numberOfSectionsInTableView(tableView: UITableView) -> Int { return fetchedResultsController.sections!.count } func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { let sectionInfo = fetchedResultsController.sections![section] as NSFetchedResultsSectionInfo return sectionInfo.numberOfObjects }
Finally, the way you access data to populate your cell in cellForRowAtIndexPath is:
let mySwim = fetchedResultsController.objectAtIndexPath(indexPath) as Swim cell.textLabel.text = date cell.detailLabel.text = mySwim.totalTime.stringValue + " mins" }
where date would be the formatted value of course.
Well it has been a long journey. I hope you learned enough about Healthkit to feel comfortable enough to start working on your own app.
Have a good one!
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