Categories
Blocks Closures iOS Swift

HealthKit for iOS8: Part 4

iOS 8 HealthKit Santiapps Marcio Valenzuela
iOS 8 HealthKit

Ok so the Journal view controller was quite simple.  Let’s take another quick break by looking at an even simpler view controller, the FoodPicker:

import Foundation

import UIKit

import HealthKit

class FoodPickerViewController: UITableViewController {

var selectedFoodItem: FoodItem?

let FoodPickerViewControllerTableViewCellIdentifier:NSString = "cell"

let FoodPickerViewControllerUnwindSegueIdentifier:NSString = "FoodPickerViewControllerUnwindSegueIdentifier"

var foodItems: NSArray = NSArray()

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?

}

Here we are looking at imports, subclassing UITableViewController and property declarations.

Our first property is selectedFoodItem, which will be set to whatever value the user selects from this tableview as an item that he or she consumed.  Then we have 2 identifiers, one for our tableviewcell and another for our unwind segue.  Remember to set both in the storyboard.  To set the cell identifier you must select the cell in the tableview and for the unwind segue you must select the segue from the “Add” button in Journal to the FoodPicker.  Then we create an array to store the hard coded values of our FoodItems.  Ideally you might want to pull this data from a web service.

Notice we use the NSEnergyFormatter here again.  You could also just create a class for this and access it globally.  Finally we add our health store variable.

Now let’s look at our viewDidLoad method:

override func viewDidLoad() {

super.viewDidLoad()

self.foodItems = [FoodItem(name: "Wheat Bagel", joules:240000.0),

FoodItem(name: "Bran with Raisins", joules:190000.0),

FoodItem(name: "Regular Instant Coffee", joules:1000.0),

FoodItem(name: "Banana", joules:439320.0),

FoodItem(name: "Cranberry Bagel", joules:416000.0),

FoodItem(name: "Oatmeal", joules:150000.0),

FoodItem(name: "Fruits Salad", joules:60000.0),

FoodItem(name: "Fried Sea Bass", joules:200000.0),

FoodItem(name: "Chips", joules:190000.0),

FoodItem(name: "Chicken Taco", joules:170000.0) ]

}

Nothing special here, just hardcoding some FoodItems into our array.  So now our tableview methods:

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

return self.foodItems.count

}

override func tableView(tableView: UITableView?, cellForRowAtIndexPath indexPath: NSIndexPath?) -> UITableViewCell {

let cell: UITableViewCell = self.tableView.dequeueReusableCellWithIdentifier(FoodPickerViewControllerTableViewCellIdentifier, forIndexPath:indexPath!) as UITableViewCell

var foodItem: FoodItem = self.foodItems[indexPath!.row] as FoodItem

cell.textLabel.text = foodItem.name

cell.detailTextLabel?.text = energyFormatter.stringFromJoules(foodItem.joules)

return cell;

}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

NSLog("performing unwind segue from FOODPICKER!")

if (segue.identifier == FoodPickerViewControllerUnwindSegueIdentifier) {

var indexPathForSelectedRow: NSIndexPath = self.tableView.indexPathForSelectedRow()!

self.selectedFoodItem = self.foodItems[indexPathForSelectedRow.row] as? FoodItem

}

}

There, now that’s a nice breather.   We set our rows according to the number of items in the array, set our cell values in the same way we did before.  And in our prepareForSegue method, we check our identifier and then set our own selectedFoodItem property from whatever the user selected.

Ok so you’ve had 2 easy classes to rest.  Now let’s get into the longest one, Part 5.

Categories
iOS Iphone Developer Swift

Swift Optionals Quick Reference

Swift Optionals Quick Reference for Newbies by Santiapps.com
Swift Optionals Quick Reference for Newbies by Santiapps.com

Optionals confuse me so I wrote this post and hope it can be of some help.

OPTIONALS

Takeaway #1: Optionals are used to declare a variable but are not assigned a value at start

Takeaway #2: Optionals contain a Some or None value, they DONT contain a String or Array or whatever else.

Takeaway #3: Therefore we MUST unwrap the value of an Optional to see what the prize is 🙂 In other words, to access its value!

Takeaway #4: DECLARATION OPTIONS

A) Using the following syntax: var someVar? – You will mostly use this…

B) Using “var someVar!” <Implicitly unwrapped> – Unfortunately UIKit & other Apple frameworks will use a lot of these…

… NEED TO EXPLORE THE DIFFERENCE BETWEEN ? and ! declarations…

Turns out you can declare a variable as an implicitly unwrapped optional if you know it will, at some point, be non-nil.  So for example, in this SO post (http://stackoverflow.com/questions/24006975/why-create-implicitly-unwrapped-optionals) they talk about have viewDidLoad in a view controller call a setter upon load:

var screenSize: CGSize?

override func viewDidLoad() {

super.viewDidLoad()

screenSize = view.frame.size

}

We know that screenSize will be filled because viewDidLoad WILL be called.  Then later we do:

@IBAction printSize(sender: UIButton) {

println(“Screen size is: \(screenSize!)”)

}

We know screenSize will have a value if its ever called.  So we can instead declare it as an implicitly unwrapped optional with a ! instead of a ? in the initial var declaration.  But don’t sweat this so much right now.

Takeaway #5: ACCESS (UNWRAPPING) OPTIONS 

Takeaway #6: Method 1: Traditional (Risky): if var != nil and then access it inside the if block.

if yourOptionalTypeOrOptionalReturningFunction != nil {

doSomethingWith(tempOptional!) || setSomeValue = tempOptional!

}

But to access it you have to unwrap the present 🙂  To do this you use the bang operator !  Whenever you use the ! you are ‘force unwrapping’ a variable, which means it will open it no matter what.  If nil is in there…KABOOM!  Bye bye Moose & Squirrel!  So you better have checked before hand.

Takeaway #7: Method 2: Optional Binding (aka:”if-let nil check”) (Safer): This means you use:

if let tempOptional = yourOptionalTypeOrOptionalReturningFunction {

doSomethingWith(tempOptional) || setSomeValue = tempOptional

}

This is more safe because it checks first or peeks in the box so to speak.  Thus you can use the variable without unwrapping.

< If you remove default value from a ? and have a ! to access it in code, your code will fail if-check will go to else.>

Takeaway #7: Method 3: Implicitly Unwrap: Uses ! operator (assumes var contains some value). But remember from Method 1, if nil, KABOOM!!!!!!

<If you remove default value from a ? and have a ! to access it in code, you get runtime crash = error = “can’t unwrap optional.None”>

Takeaway #8: Optionals unwrapped using? – This one is still kinda confusing to me. Has to do with optional chaining and inline downcast syntax I believe.  It means that when you have many optionals.  Let’s assume you have a class with 2 optional variables, name? and price?  Let’s pretend you write a function that creates a new Stock() class object and must therefore set name & price variables for it.  We would first have to check if one is set and then the other:

if let someName = stock.name {

if let somePrice = stock.price {

//now we can do something with price…

}

}

This would get messy.  So we chain them into a single statement like so:

someVariableWeWantToSet = stockName?.stockPrice

Takeaway #10: Many ObjC framework objects are optionals? and many are implicitly unwrapped! when passed into functions because they will start out as nil (UILabels, MKAnnotationViews or MKPolylines) but we know they will eventually get filled in because that’s why we put them there in the first place:

MKAnnotationView!

MKAnnotation!

UIControl!

MKPinAnnotationView!

MKMapView!

Takeaway #11: When we have something like an MKAnnotation! is received in a function as annotation. If we wish to use its super class properties, we must be inline downcast to while if-let checking. Once inside we can implicitly (force) unwrap MKPinAnnotationView! because we know since the annotation exists, it will have a view. For example, in this method:

func mapView(mapView: MKMapView!, rendererForOverlay overlay: MKOverlay!) -> MKOverlayRenderer! {

if let polylineOverlay = overlay as? MKPolyline {

let renderer = MKPolylineRenderer(polyline: polylineOverlay) renderer.strokeColor = UIColor.blueColor()

return renderer

}

return nil

}

We can interpret that funky as? as follows: “If when I get the variable overlay and unwrap it, it downcasts successfully to a MKPolyline && I get a value (not-nil) then put it into polylineOverlay & continue…” Hope this helps…

Categories
Iphone Developer Swift

Swift Tutorial II

Ok so in the first tutorial we covered let, which is the keyword for defining constants.

let thisBeAConstant = 3.141

Now we are going to cover variables, which use the var keyword like so:

var thisVariable = time

Notice 2 things about Swift:

1) We don’t use ; at the end of a line.  That’s just weird 🙂

2) We don’t have to specify the type.  The type is inferred by whatever value you pass in, so:

var someString = “this is a string”

var someInteger = 5

So Swift is kinda smart.  Now let’s meet some old friends “Hao jiu bu juan”

ARRAYS

var energies = [“solar”“wind”“fossil”, “this is a mixed array”, 39]

var energies:String[] = [“solar”“wind”“this is a string array”]

And of course we can perform some basic operations such as:

READ

var item1 = energies[0]   // “solar”

INSERT

energies.insert(“hydro”, atIndex: 2)

MODIFY

energies[3] = “geothermal”

APPEND

energies.append(“nuclear”)

or

energies += “nuclear”

COMBINE

energies += [“biomass”“hamster”]

COUNT

var lengthofArray = energies.count

LOGIC

var arrayIsEmpty = energies.isEmpty

REMOVE

energies.removeAtIndex(3)
energies.removeLast()
energies.removeAll(keepCapacity: true)
MUTATE
If we used let energies, then our array is immutable, vs if we used var energies which means its mutable.
Easy as pie.
DICTIONARIES

var energies = [

    “Solar”“Thermal”,
    “Photovoltaic” : “Grid”,
    “Nuclear” : “Dangerous”
]
Here our keys are Solar, Photovoltaic & Nuclear.  These keys can be strings or numeric values such as integers.
Once again we can:
READ
let cheapestSolarEnergy = energies[“Solar”]
COUNT
var energiesCount = energies.count
MODIFY
energies[“Solar”] = “PV”
REMOVE
energies[“Nuclear”] = nil;
INSERT
energies[“Geo”] = “Thermal”
and of course the value of a key can be an array or another dictionary:

var typesOfEnergy =

[
    platforms[“Solar”]: [“Thermal”“PV”“GridTied”],
    platforms[“Wind”]: [“Autonomous”“GridTied”],
    platforms[“Nuclear”] : [“Fusion”“Fission”,“Meltdown”]
]
and we would read it:
var type1 = typesOfEnergy[“Solar”][0]
See you next time! 🙂
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