HealthKit for iOS8: Part 3

HealthKit iOS8 by
HealthKit iOS8

Great!  Now let’s move on to the Journal View Controller.  It’ll be a good relax! 🙂 Ok we start out importing the frameworks we need:

import UIKit
import HealthKit

Ok now let’s declare our class properties:

class JournalViewController: UITableViewController {     
let JournalViewControllerTableViewCellReuseIdentifier: NSString = "Cell"     
var foodItems: NSMutableArray?     
var energyFormatter: NSEnergyFormatter {         
var energyFormatter: NSEnergyFormatter?         
var onceToken: dispatch_once_t = 0         
dispatch_once(&onceToken, {             
energyFormatter = NSEnergyFormatter()             
energyFormatter?.unitStyle = NSFormattingUnitStyle.Long             energyFormatter?.forFoodEnergyUse = true             
energyFormatter?.numberFormatter.maximumFractionDigits = 2         })         
return energyFormatter!     
var  healthStore:HKHealthStore? 

The first thing to note, is that once again this is UITableViewController.  However, unlike Profile, this tableview will contain dynamic, prototype cells.  Thus we need to dequeue our cells to save memory.  The first constant we need is one for our table view cell identifier.  Then we create a mutable array to hold our selected food items, which will come from the user selecting them in the FoodPicker. The next property is a bit strange.  NSEnergyFormatter is something new and health kit uses it to format energy data.  This is a computed property, which means it is computed each time you call for it.  This is basically creating an energyFormatter much in the same way you would create an dateFormatter from NSDateFormatter. Then finally there is the healthstore property which we need and set from the AppDelegate as you recall. Next up we have our view controller lifecycle methods which kick things off:

override func viewDidLoad() {         
self.foodItems = NSMutableArray()         
NSNotificationCenter.defaultCenter().addObserver(self, selector: "updateJournal", name: UIApplicationDidBecomeActiveNotification, object: nil)     }     
override func viewDidDisappear(animated: Bool) {         
NSNotificationCenter.defaultCenter().removeObserver(self, name:UIApplicationDidBecomeActiveNotification, object:nil)     

Our viewDidLoad does 2 things; instantiates a mutable array for foodItems so the user can start putting things in there and it calls updateJournal which we will write next.  This view controller also sets itself up as an observer for notifications fired whenever the app becomes active and finally in the viewDidDisappear method we remove ourselves as an observer. Now let’s write updateJournal.  The purpose of this method will be to basically update this tableview with data gotten from the FoodPicker after the user selects items he or she consumed:

func updateJournal () -> () {
var now: NSDate = NSDate()
let calendar : NSCalendar = NSCalendar.currentCalendar()       
var components: NSDateComponents = calendar.components(.CalendarUnitYear | .CalendarUnitMonth | .CalendarUnitDay, fromDate: now)
var startDate: NSDate = calendar.dateFromComponents(components)!
var endDate: NSDate = calendar.dateByAddingUnit(.CalendarUnitDay, value:1, toDate:startDate, options:nil)!

var sampleType: HKSampleType = HKSampleType.quantityTypeForIdentifier(HKQuantityTypeIdentifierDietaryEnergyConsumed)
var predicate: NSPredicate = HKQuery.predicateForSamplesWithStartDate(startDate, endDate:endDate, options:.None)

var query: HKSampleQuery = HKSampleQuery(sampleType: sampleType, predicate: predicate, limit: 0, sortDescriptors: nil) {

(query:HKSampleQuery?, results:[AnyObject]!, error:NSError!) -> Void in

if (error != nil) {
NSLog("An error occured fetching the user's tracked food. In your app, try to handle this gracefully. The error was: %@.", error)                 
if results != nil {
NSLog("Got something!")
dispatch_async(dispatch_get_main_queue(), {

for sample in results as [HKQuantitySample] {                 
NSLog("sample is= \(sample.metadata)")
let foodMetadataDict = (sample.metadata as NSDictionary)
let foodThing: AnyObject? = foodMetadataDict.objectForKey("HKMetadataKeyFoodType")                 NSLog("\(foodThing)")

let foodName = foodThing as NSString
let joules: Double = sample.quantity.doubleValueForUnit(HKUnit.jouleUnit())             
let foodItem: FoodItem = FoodItem(name: foodName, joules:joules) as FoodItem                 self.foodItems?.addObject(foodItem)
self.healthStore?.executeQuery(query)     // EXECUTE QUERY  }

Ok, its a bit long but simple.  The first few lines create a date for our query.  Then we create a sampleType for DietaryEnergyConsumed which is a data type health store can read and write.  We then create a predicate for it which basically limits the query to today.  Finally we create the query object and execute it (in the last line).

Remember, whats inside the query body is actually a completion block.  We pass the query the sampleType, dates and completion handler.  That completion handler takes a result and an error once again.  If there is an error, we log, if we get results from the query then we log that we got something!  Thats just being silly, but then the query code goes on to a dispatch queue.

This is where we will now update the UI by removing all objects in our foodItems array, and then for every HKQuantitySample in results array, we get the metadata key that we  will store in the object array as part of the FoodItem object and get it as a NSString.

Finally we get the value for that quantity and create a fully qualified FoodItem with that data.  In the end we add that FoodItem to the array and reload the table data. Well now that we mentioned FoodItem, let’s take a look at that class and it’ll help you better understand the next method which is the actual method for adding a FoodItem’s data to the health store.  So here is the FoodItem class:

import Foundation
import HealthKit

class FoodItem {
var name: NSString
var joules:  Double
init (name:NSString, joules:Double) { = name
self.joules = joules

func isEqual(object:AnyObject) -> (Bool) {
if object.isKindOfClass(FoodItem) {
return ((object as FoodItem).joules == self.joules) && ( == (object as FoodItem).name)
return false;

func description(NSString) -> (NSString){
var descriptionDict: NSDictionary = [ "name" :, "joules" : self.joules ]
return descriptionDict.description as NSString

That was short and sweet!  First we declare the properties of our FoodItem class, name and joules.  Then we create the initializer for it, important to note!  We also added an isEqual function in there to test if an object is a FoodItem type object.  Remember that FoodItem is not subclassing NSObject so it doesn’t have access to NSObject’s isEqual function.  Finally we give FoodItem a description function which basically returns its name and joules values as an NSString. Sweet!  Ok so now let’s look at the Journal view controller method that actually adds a FoodItem:

func addFoodItem (foodItem:FoodItem) {         
var quantityType: HKQuantityType = HKQuantityType.quantityTypeForIdentifier(HKQuantityTypeIdentifierDietaryEnergyConsumed)         //MUST DEFINE HKQUANTITY         
var quantity: HKQuantity = HKQuantity(unit: HKUnit.jouleUnit(), doubleValue:foodItem.joules)         //DATE & METADATA         
var now: NSDate = NSDate()         
var metadata: NSDictionary = ["HKMetadataKeyFoodType"]         
//This creates the object to SAVE         
var calorieSample: HKQuantitySample = HKQuantitySample(type: quantityType, quantity:quantity, startDate:now, endDate:now, metadata:metadata)          
NSLog("Before saving to health store in Journal...")         self.healthStore?.saveObject(calorieSample, withCompletion: { (success, error) in             NSLog("After saving to healthstore in Journal...")             dispatch_async(dispatch_get_main_queue(), {                 
NSLog("After dispatch to health store in Journal...")                 
if success {                     //MUST UPDATE TABLE in MAIN QUEUE                     NSLog("Energy Consumed Saved")                     
self.foodItems?.insertObject(foodItem, atIndex:0)                     
var indexPathForInsertedFoodItem: NSIndexPath = NSIndexPath(forRow: 0, inSection: 0)                     self.tableView.insertRowsAtIndexPaths([indexPathForInsertedFoodItem], withRowAnimation: UITableViewRowAnimation.Automatic)                 
} else {                     
NSLog("An error occured saving the food %@. In your app, try to handle this gracefully. The error was: %@.",, error)                     

It seems long, but the pattern is pretty simple.  We create the right identifier for DietaryEnergyConsumed, we create a quantity from the FoodItem we passed into this method, specifically from its joules value.  We create a date and give it some metadata in order to complete the creation of our HKQuantitySample.  Finally we saveObject to the health store and in its completion block, if success we log Energy Consumed Saved, insert the newly selected item into the foodItems array and update the tableview.  Otherwise we log the error. Finally let’s look at our tableview methods and our segue method because remember that from this Journal view controller we will allow the user to tap the “Add” button to take us to the FoodPicker which we will analyze next.  So here are our tableview and segue methods:

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {         return self.foodItems!.count     }

We set our numberOfRowsInSection to the items in our mutable foodItems array.

override func tableView(tableView: UITableView?, cellForRowAtIndexPath indexPath: NSIndexPath?) -> UITableViewCell {         
let cell: UITableViewCell = self.tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath:indexPath!) as UITableViewCell          
var foodItem: FoodItem = self.foodItems?[indexPath!.row] as FoodItem         cell.textLabel.text =          
cell.detailTextLabel!.text = energyFormatter.stringFromJoules(foodItem.joules)         
return cell;     

Here we dequeue a cell as always and create a FoodItem according to the indexPath!.row and get its name and joules into the cell.

func performUnwindSegue(segue:UIStoryboardSegue) { //was typed as ibaction...         
var foodPickerViewController: FoodPickerViewController = segue.sourceViewController as FoodPickerViewController         
var selectedFoodItem: FoodItem = foodPickerViewController.selectedFoodItem! as FoodItem       self.addFoodItem(selectedFoodItem)     

As for the segue, this is the initiating view controller, so we need an unwind because when the user finishes selecting an item in the FoodPicker, we must do some stuff.  What stuff?  Well first we get our sourceViewController for the “unwind” segue.  Don’t get confused because normally you get the destination segue of a forward segue in order to set that destination view controller’s properties.  In this case, we are in the calling view controller and we are unwinding from a segue.  Our source view controller is FoodPicker and our destination is Journal.  We then take the source’s selectedFoodItem property and set it as a local variable called selectedFoodItem here, locally, in Journal.  Then we call our addFoodItem() method passing it in that local variable selectedFoodItem.  That saves that food item’s name in metadata and its joules into the health store as DietaryConsumedEnergy. Well, that was quite simple.  The FoodPicker is actually quite simple.  See you there!


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