Swift (general)

Question 1

What is a UIEelement?

Answer 1

It’s an object class in the view controller (eg a button)

Question 2

What is an @IBAction?

Answer 2

@IBActions are connected to UIElements (eg a button). They call code when the button is tapped. Connects ViewController (eg with button) to the code - eg button is controlling the code execution.

Question 3

What is an @IBOutlet

Answer 3

@IBOutlets are connected to UIElements (eg button). They change the look of the UIElement (button) in the ViewController. Connects code to ViewController - eg the code changes the look of the button.

Question 4

What is UINavigation Controller?

Answer 4

UINavigation Controller is a class that lets you navigate between different UIViewControllers (ie screens). It can handle a stack of different UIViewControllers (ie the screens). The first stack is called the rootViewController

Question 5

What does AVFoundation framework do?

Answer 5

It deals with audio and video

eg AVAudio class

Question 6

What is an AVAudioSession?

Answer 6

Need to record and playback audio. There’s just one that exists for the entire time the app is running. You grab it with the .sharedInstance() method - ie AVAudioSession.sharedInstance()

Question 7

What does NSSearchPathForDirectoriesInDomains

Answer 7

Creates a list of directory search paths

Question 8

What is delegation?

Answer 8

When you get one object to do the job of anothers

Question 9

What is a gesture recogniser?

Answer 9

A subclass of UIGestureRecogniser that detects a specific touch sequence and calls an action on its target when the sequence is detected. eg pinch, swipe, tap

Question 10

What is the scene dock?

Answer 10

It’s the row of icons above the canvas (ie ViewController)

Question 11

What does ctrl + dragging from ViewController (yellow circle) to the UIElement (eg button) do?

Answer 11

It connects an @IBOutlet

Question 12

What does ctrl + dragging from a UIElement (eg button) to the ViewController (yellow circle)?

Answer 12

It connects an @IBAction

Question 13

What is a tag?

Answer 13

Found in the Attributes Inspector, a tag is an integer that you can use to identify View objects in your app

(Related method is -[UIView tag]

Question 14

What is a framework?

Answer 14

A framework a shared library of of code that includes associated resources such as interface files and images (eg MKMapView) (can be added in xcode using imports UK for eg)

Question 15

What is UITabBarController?

Answer 15

UITabBarController is an array of view controllers. It also has a tab bar at the bottom of the screen with a tab for each view controller in its array.

Question 16

What is a function?

Answer 16

A function is a self contained piece of code that performs a specific task. The three types in swift are Global Functions, Nested Functions, and Methods

Question 17

Where are Global Functions?

Answer 17

Global Functions are functions that can be called from anyplace in an app (ie in a class) (eg print, min, and abs)

Question 18

What is a Method (function)?

Answer 18

When a function is defined in, and associated with a particular class, it is called a Method.

Question 19

When do you use dot syntax?

Answer 19

eg append is a method. A function that’s part of the String class. So we call the append Method on an instance of the string class using dot syntax

Question 20

What is a class?

Answer 20

A class is a unit we use to package together related data and functionality.

Question 21

What is an instance of a class?

Answer 21

One of its moving parts. (eg think of Mouse Trap. One of the wheels is an instance of a class)

Question 22

What makes up a class?

Answer 22

A class is made up of properties and methods
eg properties
let title: String
let releaseYear: Int
eg methods (every class needs an init method)
init()

Question 23

Breakdown:
class Movie {
let title: String
let releaseYear: Int

init(title: String, releaseYear: Int) {
self.title = title
self.releaseYear = release year
}

Answer 23

class Movie {
let title: String
let releaseYear: Int

^*PROPERTIES
*INITALISE BELOW

init(title: String, releaseYear: Int) {

self. title = title
self. releaseYear = release year

^*USING self. BECAUSE THE PARAMETERS IN THE init() HAVE THE SAME NAMES AS THE PROPERTIES. USE self. TO REPRESENT THE OBJECT BEING INITIALISED.
}

Question 24

What are Type Properties? (aka Class Properties)

Answer 24

There belong more to the class, and not objects within the class. They don’t vary across classes, so their value stays the same.
ie it has the same value for every instance of a class
eg
static let permittedRatings = [“G”, “PG”]
OR
class let permittedRatings = [“G”, “PG”]

Question 25

What is a Computed Property?

Answer 25

A property that's based on computed data in the class
eg the average of a range of scores

(Nb they have getters and setters)

Question 26

What are Instance Methods?

Answer 26

Instance Methods are called on instances of the class

eg returning a list of movies that were produced in 1986

Question 27

What are Class Methods?

Answer 27

These belong to the entire class

eg
isSourceTypeAvailable belongs to the UIImagePickerController class

(nb source type will be a photo album or camera)

Question 28

What happens if you use ‘class’ instead of ‘static’ for Class Method?

eg
class func isSourceTypeAvaiable

Answer 28

If you use ‘class’ instead of ‘static’ subclasses will be able to override the method

Question 29

What are enums? What are structs?

Answer 29

Enums define a set of related values. Structs are a convenient way to bundle properties together. They can have their own methods and conform to protocols

enum PrimaryColour {
case red
case green
case blue
}

or enum PrimaryColour {
case red, green blue
}

Question 30

What is the difference between Structs/Enums and Classes?

Answer 30

Structs/Enums are value types, while Classes are reference types

Question 31

Between Classes, Enums, and Structs, which have inheritance?

Answer 31

Only classes have inheritance (ie subclasses inherit from the parent class)

Question 32

What are protocols and extensions?

Answer 32

Protocols and extensions are tools used to package models of functionality that expand on classes, enumerations and structs. Protocols can be shared across classes, and extensions are used to customise existing classes. The both allows you to reuse code and dry program (don’t repeat yourself).

Question 33

Describe protocols in more detail

Answer 33

A protocol is a list of related method signatures. Adopting a protocol is like signing a method to implement every method on the list (eg anything that conforms to Apple’s built in comparable protocol can be compared). Protocols are an essential component of the delegate pattern, the patter by which one type calls upon another type to perform some operation.

Question 34

What are extenstions?

Answer 34

Extensions offer a way to add computed properties and methods to an existing class, struct, or enum. They are often used to extend types for which you don’t have access to the code (eg apple frameworks, or third party libraries)

Question 35

What do closures include?

Answer 35

Closures include global functions, nested functions, and closure expressions

Question 36

What is a closure expression?

Answer 36

A closure expression is an unnamed, self contained block of code that can be passed as an argument to a function. Closure expressions are used to specify an action to be executed at some time in the future.

Question 37

Simplify a closure expression using shorthand arguments

Answer 37

var soups = ["tomato", "french onion"]
var sortedSoups = soups.sort({ (soup1: String, soup2: String) -> Bool in 
return soup2 > soup1
})

var sortedSoups = soups.sort({
      $1 > $0
})

The closure expression parameter and return types can be inferred…so no need for ‘String’ and ‘Bool’ and ‘->’. Since this is a single expression closure, it can be inferred that it returns the result of that single expression, so we can also leave out ‘return’. We can use the shorthand argument names, $0 and $1 for soup1 and soup2, so no need for these.

Question 38

Describe the ways of connecting the switches in ColorMaker

Answer 38

1. For Red switch: in the ‘View Controller Scene’ ctrl click. Drag ‘Value Changed’ to the yellow View Controller on Storyboard. Select the desired method (ie changeColorComponent). This connects the switch to the method. Then drag from ‘New Referencing Outlet’ to the yellow ViewController icon to connect the switch to the redControl @IBOutlet redControl swich
2. For Green switch; an easier method. Just drag the Green button to the method in ViewController.swift (ie the block of code). This will connect all the above.

Question 39

What are UIControl classes?

Answer 39

UIControl are the classes that turn user input (eg a touch) into events using the target/action pattern.

Question 40

Explain sliders and changing colours

Answer 40

Here’s a trick that will come in handy. The sliders will give you a Float value between 0 and 1, but the UIColor object must be constructed with CGFloat values.

If you have a Float and you need a CGFloat you can use the CGFloat constructor to convert between them

let f: Float = 0.5
let cgf: CGFloat = CGFloat(f)