HealthKit for iOS8: Part 7

iOS 8 HealthKit Santiapps Marcio Valenzuela
iOS 8 HealthKit

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.

HealthKit for iOS8
HealthKit for iOS8

Now embed it!

HealthKit for iOS8
HealthKit for iOS8


Your final storyboard should look like this:

HealthKit for iOS8
HealthKit for iOS8


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:

HealthKit for iOS8
HealthKit for iOS8


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() {


let bundle = NSBundle.mainBundle()

let modelURL = bundle.URLForResource("SwimModel", withExtension:"momd")

model = NSManagedObjectModel(contentsOfURL: modelURL!)!



psc = NSPersistentStoreCoordinator(managedObjectModel:model)



context = NSManagedObjectContext()

context.persistentStoreCoordinator = psc



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)")





func saveContext() {

var error: NSError? = nil

if context.hasChanges && ! {

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() {


//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 = NSDate()



//Add object to array



//Refresh UI



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( as NSDate)


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:

HealthKit for iOS8
HealthKit for iOS8

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( as NSDate)


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.


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 = NSDate()


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)")




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]


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:

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!

HealthKit for iOS8: Part 6

iOS 8 HealthKit Santiapps Marcio Valenzuela
iOS 8 HealthKit

Here is the start of our WorkOut view controller:

import Foundation
import UIKit
import HealthKit

class WorkoutViewController: UITableViewController, UITextFieldDelegate {

@IBOutlet var numberOfLapsTextField: UITextField!
@IBOutlet var metersPerLapTextField: UITextField!
@IBOutlet var workoutDurationTextField: UITextField!
@IBOutlet var paceTextField: UITextField!
var numberOfLapsValue: NSString?
var metersPerLapValue: NSString?
var workoutDurationValue: NSString?
var userWeight: Double?
var  healthStore:HKHealthStore?

We import what we need, we subclass UITableViewController and add the Text Field delegate protocol.  Here I have created 4 labels for:

  • numberOfLaps
  • metersPerLap
  • workoutDuration
  • pace

These labels have an underlying variable for each.  The reason the first 3 are strings is because these are not health kit data per se.  These will be stored in CoreData.  However they really should be NSNumbers because it would be quite nice to store them and take advantage of CoreData’s ability to retrieve ordered data and statistical data in its fetches as well.

Finally we declare our health store property.

First let’s look at our lifecycle methods:

override func viewDidLoad() {




func textFieldShouldReturn (textField: UITextField) -> (ObjCBool) {


if self.numberOfLapsTextField != nil && self.metersPerLapTextField != nil && self.workoutDurationTextField != nil {


return true;


In viewDidLoad we call a fetchUsersWeight method because we will need that to calculate calories burned.  Then we implement textFieldShouldReturn for each label.  Let’s take a look at that first method called:

func fetchUsersWeight() -> () {

var todayPredicate: NSPredicate = self.predicateForSamplesToday()

var weightType: HKQuantityType = HKObjectType.quantityTypeForIdentifier(HKQuantityTypeIdentifierBodyMass)

self.healthStore?.aapl_mostRecentQuantitySampleOfType(weightType, predicate: todayPredicate, completion: { (weight, error) -> () in

if weight == nil {

NSLog("Sorry, weight is empty...")



if let someWeight = weight {

var weightUnit: HKUnit = HKUnit.poundUnit()

self.userWeight = weight!.doubleValueForUnit(weightUnit)




Once again we make a fetch using the same extension method and helper predicate method as before.  This exemplifies the use of extensions because we need to include the predicate method in this Workout class, not so the extension.  So go ahead and add the predicate method now:

func predicateForSamplesToday () -> (NSPredicate) {

let calendar: NSCalendar = NSCalendar.currentCalendar()

let now: NSDate = NSDate()

let startDate: NSDate = calendar.startOfDayForDate(now)

let endDate: NSDate = calendar.dateByAddingUnit(.CalendarUnitDay, value:1, toDate:startDate, options:nil)!

return HKQuery.predicateForSamplesWithStartDate(startDate, endDate:endDate, options:HKQueryOptions.StrictStartDate)


Ok so the user has 2 options here: Done or Cancel.  Cancel is easy:

@IBAction func cancel(sender: AnyObject) -> () {



Now let’s take a look at Done:

@IBAction func saveMyWorkout(sender: AnyObject) -> () {

//1.  Enter the values for your workout & capture

numberOfLapsValue = numberOfLapsTextField.text

metersPerLapValue = metersPerLapTextField.text

workoutDurationValue = workoutDurationTextField.text

//A - Need to fetch the user's weight in kgs from healthstore

var myWeight: Double = self.userWeight! * 0.453

//B - Need to convert time worked out into hours

//C - Need to select pace from some sort of switch

var pace: Double = (paceTextField!.text as NSString).doubleValue

//D - Throw away numberOfLaps = (numberOfLapsValue! as NSString).doubleValue & (metersPerLapValue! as NSString).doubleValue

var totalCaloriesBurnedByWorkout: Double =  ( (myWeight * pace) ) * ((workoutDurationValue! as NSString).doubleValue)/60

var totalJoulesBurnedByWorkout: Double = totalCaloriesBurnedByWorkout*4.184

//1.5 Set to EnergyVC before saving

let energyVCInstance: EnergyViewController = self.navigationController!.viewControllers[0] as EnergyViewController

energyVCInstance.activeEnergyBurnedValueLabel?.text = NSString(format:"%.2f",totalJoulesBurnedByWorkout)

energyVCInstance.activeEnergyBurned = totalJoulesBurnedByWorkout


//2.  Dismiss and set values on EnergyVC such that they can be saved to the healthStore

//Save object to healthstore


var quantityType: HKQuantityType = HKQuantityType.quantityTypeForIdentifier(HKQuantityTypeIdentifierActiveEnergyBurned)


var quantity: HKQuantity = HKQuantity(unit: HKUnit.jouleUnit(), doubleValue:totalJoulesBurnedByWorkout)


var now: NSDate = NSDate()

var metadata: NSDictionary = ["HKMetadataKey":"Swim Session"]


var workoutType = HKWorkoutActivityType.Swimming

//This creates the object to SAVE

var energyBurnt: HKQuantitySample = HKQuantitySample(type: quantityType, quantity:quantity, startDate:now, endDate:now, metadata:metadata)

NSLog("Before saving to the healthstore...")

self.healthStore?.saveObject(energyBurnt, withCompletion: { (success, error) in

NSLog("Saving to the healthstore...")

if (error != nil) {

NSLog("The error is: \(error)")


dispatch_async(dispatch_get_main_queue(), {

if success {

// This was for updating a uitableview

// Alert User

let alertController = UIAlertController(title: "Success!", message: "Data Saved", preferredStyle: UIAlertControllerStyle.Alert)

alertController.addAction(UIAlertAction(title: "Confirm", style: UIAlertActionStyle.Default, handler: {action in

println("confirm was tapped")

//dismiss this vc



self.presentViewController(alertController, animated: true, completion: nil)

} else {

NSLog("An error occured saving your workout burn. In your app, try to handle this gracefully. The error was: %@.", error)






This time I take you step by step, once again, inside the same method so as to drive the point home.  First we take all necessary data from labels to make our calculations.  We make our calculation and populate totalJoulesBurnedByWorkout.

Then we set the properties in our EnergyViewController from here before we return.

And before returning, we save our data to the health store, creating an identifier, then a quantity, then a date, then some metadata and finally calling saveObject.  In the saveObject method we return an alertController for success and pop our Workout view controller, because remember this is a navigation stack, not a modally presented view controller.  Else we log an error.

In the final part, we will add CoreData to our project and save laps and meters data into CoreData as well.

C ya!