iOS Development

Question 1

What do Classes and Structures have in common?

Answer 1

1. Define props to store values.
2. Define methods for functionality.
3. Define subscripts to access their values - using subscript syntax.
4. Define initializers to setup state.
5. Extend functionality beyond their default implementation.
6. Conform to protocols for standard functionality.
7. Contain Stored props as variables &/or constants.
8. Use initializer syntax for new instances.
9. Use dot notation to assign a new variable value or access props from their instances.

Question 2

What behaviors do classes have separate from structures?

Answer 2

1. Ability for inheritance.
2. Type-casting.
3. Ability for de-initializing.
4. Reference counting (1+ reference to a class instance).
5. Is a “reference type”.

Question 3

What behaviors do structures have separate from classes?

Answer 3

1. Considered a “value type”.

2. Auto generated member-wise initializer for new instances.

Question 4

What are “Optionals”?

Answer 4

A type that represents either. a wrapped value or “nil”.

Question 5

Define “nil”

Answer 5

The absence of value.

Question 6

When do you use an Optional?

Answer 6

If you cannot guarantee that a “prop”, “method”, or “subscript” will return a value.

Question 7

How do you identify an Optional value?

Answer 7

With a trailing “?” after a type’s name. Ex: let sample = Int?

Question 8

Is the Optional Type an enumeration?

Answer 8

Yes.

Question 9

What are the two cases of the Optional Type?

Answer 9

Optional.none = "nil" literal
Optional.some(wrappedValue) = storing a wrapped value.

Question 10

What are the different ways you can unwrap an Optional?

Answer 10

1. Binding
2. Chaining
3. “Nil-Coalescing-Operator”
4. Unconditional
5. Forced

Question 11

What is Optional Binding?

Answer 11

Conditionally binding a wrapped value of an Optional Instance to a new variable; using a “Optional Binding Control Structure”.

Question 12

What are the “Optional Binding Control Structures”?

Answer 12

“if let”, “guard let”, & “switch”

Question 13

What is “Optional Chaining”?

Answer 13

Use (postfix ?) the postfix optional chaining operator to access the props and methods of a wrapped instance.

EX: (hasSuffix is the postfix operator)
if imagePaths[“star”]?.hasSuffix(“.png”) == true { print(….) }

Question 14

What is Optional unwrapping with a “nil-coalescing operator”?

Answer 14

It provides a default value incase the optional value is “nil”. “??”

EX:  
let sample = answer1 ?? answer2

Question 15

What is Unconditional Unwrapping (aka forced unwrapping) with optionals?

Answer 15

You have to been 100% certain that the instance contains a value.

Use the unwrap operator “!”

EX:
let number = Int("42")!

This can also be used in chaining.

EX:
let number = path["sample"]!.hasSuffix(".png")

Question 16

What is an initializer?

Answer 16

Creates an instance that stores a given value.

EX:
instanceName init(nilLiteral: () )