Doubts from CS193P Lectures 1-4

a) Presence1 with TableViewController.  Why the initWithNibName method in the DetailController.m contains no specific values except for the title setter? Couldnt i just set this title in the viewDidLoad?

b) Why if we call
NSMutableString *string = [[NSMutableString alloc] init]; we must later release it.  But if we called NSMutableString *string = NSMutableString string]; then we dont have to cause itll be autoreleased in the pool.  If this is so, why would we even bother calling it the first way?c) MoveMeApp from Apple Dev Center.  The placard.png image is ‘imported’ by the UIImage line in the init.  And the a CGRect frame is created based on the size of that image.  Is this app importing that image into the CGRect frame created or is it importing the image and ‘tracing a frame with the exact features of the imported png image? In other words, is it actually re-drawing the png or is it just placing it inside a frame container?

d) On Warmup 2, i get the Dictionary was mutated while being enumerated.  Ok, but isnt it a MUTABLE type dictionary? I guess that means you can change its contents later, just not during a thread operation.  Maybe something to do with the fact that the dictionary would have had to be copied?

e) in the debugger window, i dont know what the register window tells you? in debugging splitter2 i get 0×20(%edx),%edi with a red arrow left of it and so i step into it and i get a EX_BAD_ACCESS.  I found the error in code; NSString *string didnt have an assignment so the function isnt passed a value.  my question is, how does debugger point me to that mistake IN the code? cause luckily this code was short, what if it were HUGE?!  im missing something obviously.

f) i cant find anything wrong with warmup 3

g) in splitter3 i found the assign vs retain property.  I know that retain bumps up the reference count on words object vs assign which changes its value.  but the wrong example is #3 where assign is used.  and since this is NSArray object, it cant be assigned a value?  so i tried converting it to a NSMutableArray and it didnt work.  Because i think i needed then to define a setter method for it but didnt know how?

Saving HealthKit Data & Closures

iOS 8 HealthKit Santiapps Marcio Valenzuela
iOS 8 HealthKit

This code bit saves:

  healthKitStore.saveObject(bmiSample, withCompletion: { (success, error) -> Void in
    if( error != nil ) {
      println("Error saving BMI sample: \(error.localizedDescription)")
    } else {
      println("BMI sample saved successfully!")
    }
  })

The method signature is:

saveObject(object: HKObject!, withCompletion completion: ((Bool, NSError!) -> Void)!)

This method takes an HKObject which is bmiSample

and it takes a completion closure which itself takes a bool & error and returns void.

So in our method call, we pass in the bmiSample as the HKObject and for the success and error completion block we say:

if error is NOT nil then log that error’s description,

else log that the bmiSample was saved successfully.

 

 

This code bit reads:

// 2. Call the method to read the most recent weight sample
self.healthManager?.readMostRecentSample(sampleType, completion: { (mostRecentWeight, error) -> Void in
 
  if( error != nil )
  {
    println("Error reading weight from HealthKit Store: \(error.localizedDescription)")
    return;
  }
 
  var weightLocalizedString = self.kUnknownString;
  // 3. Format the weight to display it on the screen
  self.weight = mostRecentWeight as? HKQuantitySample;
  if let kilograms = self.weight?.quantity.doubleValueForUnit(HKUnit.gramUnitWithMetricPrefix(.Kilo)) {
    let weightFormatter = NSMassFormatter()
    weightFormatter.forPersonMassUse = true;
    weightLocalizedString = weightFormatter.stringFromKilograms(kilograms)
  }
 
  // 4. Update UI in the main thread
  dispatch_async(dispatch_get_main_queue(), { () -> Void in
    self.weightLabel.text = weightLocalizedString
    self.updateBMI()
 
  });
});

Here we are calling the .readMostRecentSample method which has this signature:

func readMostRecentSample(sampleType:HKSampleType , completion: ((HKSample!, NSError!) -> Void)!)

This method takes an HKSampleType which is sampleType

and it takes a completion closure which itself takes an HKSample & error and returns void.

So in our method call, we pass in the sampleType as the HKSample and for the success and error completion block we say:

if error is NOT nil then log that error’s description,

else get that mostRecentWeight as self.weight, format it and set it as the label’s text.

How does this method get the actual value from the HKHealthStore?  Inside itself, it executes an HKQuery which itself says this:

let sampleQuery = HKSampleQuery(sampleType: sampleType, predicate: mostRecentPredicate, limit: limit, sortDescriptors: [sortDescriptor])
    { (sampleQuery, results, error ) -> Void in
 
      if let queryError = error {
        completion(nil,error)
        return;
      }
 
      // Get the first sample
      let mostRecentSample = results.first as? HKQuantitySample
 
      // Execute the completion closure
      if completion != nil {
        completion(mostRecentSample,nil)
      }
  }
  // 5. Execute the Query
  self.healthKitStore.executeQuery(sampleQuery)

Give me:

a.  sampleType

b.  a predicate, limit, sortDescriptors

c. and a completion closure which takes a sampleQuery, results & error

such that;

if error it NOT nil, set the readMostRecentSample method’s completion closure to nil,error

otherwise set the completion closure with the results and no error.

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() {

//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:

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(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!