iOS Apprentice

Question 1

What happens when you press Run?

Answer 1

The compiler is the part of Xcode that converts your Swift source code into executable binary code

Question 2

The complete set of frameworks for iOS is known collectively as?

Answer 2

Cocoa Touch

Question 3

With what UIKit works to represente size on screen

Answer 3

Points

Question 4

Three possible scope levels in Swift

Answer 4

Global scope: These objects exist for the duration of the app and are accessible from anywhere.

Instance scope: This is for variables such as currentValue. These objects are alive for as long as the object that owns them stays alive.”

“Local scope: Objects with a local scope, such as the slider parameter of sliderMoved(), only exist for the duration of that method. As soon as the execution of the program leaves this method, the local objects are no longer accessible.”

Question 5

What is info.plist?

Answer 5

Info.plist is a configuration file inside the application bundle that tells iOS how the app will behave. It also describes certain characteristics of the app, such as the version number, that don’t really fit anywhere else.

Question 6

What happens if you don’t add any constraints to your views?

Answer 6

In that case, Xcode will automatically add constraints when it builds the app.”

Question 7

In order to allow Xcode to put an app on your iPhone?

Answer 7

the app must be digitally signed with your Development Certificate. A certificate is an electronic document that identifies you as an iOS application developer and is valid only for a specific amount of time.

Question 8

Apps that you want to submit to the App Store must

Answer 8

be signed with the Distribution Certificate.

Question 9

Xcode uses this to sign the app for use on your particular device (or devices)

Answer 9

Provisioning Profile

you need a provisioning profile or the app won’t go on your device.

Question 10

What the difference is between the terms property and instance variable?

Answer 10

In Swift terminology, a property is a variable or constant that is used in the context of an object. That’s exactly what an instance variable is.
(In Objective-C, properties and instance variables are closely related but not quite the same thing. In Swift they are the same.)”

Question 11

Cleaning code flow

Answer 11

When write code until it becomes messy and then you clean it up. After a little while it becomes a big mess again and you clean it up again.

Question 12

NSRange vs. Range

Answer 12

NSRange is an Objective-C structure whereas Range is its Swift equivalent - they are similar, but not exactly the same. So, while an NSRange parameter is used by the UITextField (which internally, and historically, is Objective-C based) in its delegate method, in our Swift code, if we wanted to do any String operations, such as replacingCharacters, then we need a Range value instead. Swift methods generally use Range values and do not understand NSRange values, which is why we converted the NSRange value to a Swift-understandable Range value.

Question 13

Segue flow in steps

Answer 13

Question 14

Equal vs identical

Answer 14

If you use ==, you’re checking whether two variables have the same value.”
“With === you’re checking whether two variables refer to the exact same object.

Question 15

UInt vs Int

Answer 15

The U stands for unsigned, meaning the data type can hold positive values only. It’s called unsigned because it cannot have a negative sign (-) in front of the number.

Question 16

CGFloat vs Float

Answer 16

CGFloat. This isn’t really a Swift type but a type defined by the iOS SDK. It’s a decimal point number like Float and Double. For historical reasons, this is used throughout UIKit for floating-point values. (The “CG” prefix stands for the Core Graphics framework.)

Question 17

%f vs %.8f

Answer 17

The .8 means that there should always be 8 digits behind the decimal point.

Question 18

UI objects hierarchy from NSObject

Answer 18

Question 19

assert() in code

Answer 19

An assertion is a special debugging tool that is used to check that your code always does something valid. If not, the app will crash with a helpful error message.

Assertions are usually enabled only while you’re developing and testing your app and disabled when you upload the final build of your app to the App Store

Question 20

Unwind segue

Answer 20

Unwind segue closes the active scree

Question 21

Mutating keyword

Answer 21

When a method changes the value of a struct, it must be marked as mutating. Recall that String is a struct, which is a value type, and therefore cannot be modified when declared with let.

You don’t need to use the mutating keyword on methods inside a class because classes are reference types and can always be mutated, even if they are declared with let

Question 22

“appearance proxy”

Answer 22

to change the look of all of the controls of a particular type at once.”

Question 23

common technique for building complex layouts

Answer 23

Grouping views in a container view

Question 24

Associated values in enums

Answer 24

They let you associate a custom value (or values) with each enumeration case.

1. Each enumeration case has zero or more associated values.
2. The associated values for each enumeration case have their own data type.
3. You can define associated values with label names like you would for named function parameters.

Question 25

An enumeration can have raw values and associated values?

Answer 25

An enumeration can have raw values OR associated values, but not both.

Question 26

associated value in enum with guard

Answer 26

Question 27

Enumerations without any cases

Answer 27

*Uninhabited enumerations*can be used as namespaces and prevent the creation of instances.

Question 28

Required init - when?

Answer 28

If you conform to a protocol with required initializers using a class type, those initializers must use the required keyword:

Question 29

Your choices for implementing a get requirement in protocol are

Answer 29

* A constant stored property.
* A variable stored property.
* A read-only computed property.
* A read-write computed property.

Question 30

Associated types in protocols

Answer 30

using associatedtype in a protocol, you’re simply stating there isa type used in this protocol, without specifying what type this should be. *It’s up to the protocol adopter to decide what the exact type should be.*

Question 31

Protocol composition

Answer 31

Imagine you need a function that needs access to the Vehicle protocol’s stop() function and the Wheeled protocol’s numberOfWheels property. You can do this using the & composition operator.

Question 32

If you’re designing a protocol to be adopted exclusively by classes, it’s best to

Answer 32

to request that Swift uses reference semantics when using this protocol as a type.

: class

Question 33

is a requirement for any type you want to use as a key to a Dictionary.

Answer 33

The Hashable protocol, a subprotocol of Equatable

Question 34

Type constraints

Answer 34

Pet requires that the type assigned to Animal must be a subclass of Pet, if Pet is a class, or must implement the Pet protocol, if Pet is a protocol.

class Keeper <t: animal></t:>

Question 35

Generic parameter in func

Answer 35

Generics are like functions for the compiler. They are evaluated at compile time and result in new types which are specializations of the generic type.

Think of the type parameters as arguments for the compiler, which it uses to define one possible function.

Question 36

When the collection view needs some layout information, it asks

Answer 36

your layout object to provide it by calling certain methods in a specific order: