Swift (general) Flashcards

Question

What is a Computed Property?

Answer 1

``` 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)

Answer 2

Instance Methods are called on instances of the class eg returning a list of movies that were produced in 1986

Answer 3

These belong to the entire class eg isSourceTypeAvailable belongs to the UIImagePickerController class (nb source type will be a photo album or camera)

Answer 4

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

Answer 5

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 }

Answer 6

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

Answer 7

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

Answer 8

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).

Answer 9

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.

Answer 10

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)

Answer 11

Closures include global functions, nested functions, and closure expressions

Answer 12

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.

Answer 13

``` 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.

Answer 14

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.

Answer 15

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

Answer 16

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)