Swift - LinkedIn Skill Assessments Quizzes with Answers

Darsh Jariwala
Feb 3, 2022 10 min read

Swift

Q1. What is this code an example of?

let val = (Double)6
  • a syntax issue
  • typecasting
  • assignment
  • initialization

Q2. What is the error in this code?

let x = 5
guard x == 5 { return }
  • The guard is missing the else.
  • Nothing is wrong.
  • The guard is missing a then.
  • The comparison is wrong.

Q3. What is the raw/underlying type of this enum?

enum Direction {
  case north, south, east, west
}
  • There is none.
  • String
  • Any
  • Int

Q4. Why is dispatchGroup used in certain situations?

  • It allows multiple synchronous or asynchronous operations to run on different queues.
  • It allows track and control execution of multiple operations together.
  • It allows operations to wait for each other as desired.
  • all of these answers.

Q5. What is this code an example of?

let val = 5
print("value is: \(val)")
  • string interpolation
  • string compilation
  • method chaining
  • string concatenation

Q6. What are the contents of vals after this code is executed?

var vals = [10, 2]
vals.sort { (s1, s2) -> Bool in
  s1 > s2
}
  • [10, 2]
  • [2, 10]
  • nil
  • This code contains an error

Q7. What does this code print?

typealias Thing = [String:Any]
var stuff: Thing
print(type(of: stuff))
  • Dictionary<String, Any>
  • Dictionary
  • ERROR
  • Thing

Q8. What is the value of y?

let x = ["1", "2"].dropFirst()
let y = x[0]
  • This code contains an error
  • 1
  • 2
  • nil

Q9. What is the value of test in this code?

var test = 1 == 1
  • TRUE
  • YES
  • 1
  • This code contains an error

Q10. What is the value of y?

var x: Int?
let y = x ?? 5
  • 5
  • 0
  • nil
  • This code contains an error

Q11. What is the type of this function?

func add(a: Int, b: Int) -> Int { return a+b }
  • Int
  • (Int, Int) -> Int
  • Int
  • Functions don’t have types.

Q12. What is the correct way to call this function?

func myFunc(_ a: Int, b: Int) -> Int {
  return a + b
}
  • myFunc(5, b: 6)
  • myFunc(5, 6)
  • myFunc(a: 5, b: 6)
  • myFunc(a, b)

Q13. The Codable protocol is _?

  • a combination of Encodable and Decodable
  • not a true protocol ««—Possibly correct as it’s a typealias of Encodable and Decodable
  • required of all classes
  • automatically included in all classes

Q14. What is the type of value1 in this code?

let value1 = "\("test".count)"
  • String
  • Int
  • null
  • test.count

Q15. When a function takes a closure as a parameter, when do you want to mark is as escaping?

  • when it’s executed after the function returns
  • when it’s scope is undefined
  • when is’s lazy loaded
  • all of these answers

Q16. What’s wrong with this code?

class Person {
  var name: String
  var address: String
}
  • Person has no initializers.
  • Person has no base class.
  • var name is not formatted corrrectly.
  • address is a keyword.

Q17. What is the value of names after this code is executed?

let names = ["Bear", "Joe", "Clark"]
names.map { (s) -> String in
  return s.uppercased()
}
  • [“BEAR”, “JOE”, “CLARK”]
  • [“B”, “J”, “C”]
  • [“Bear”, “Joe”, “Clark”]
  • This code contains an error.

Q18. What describes this line of code?

let val = 5
  • a constant named val of type Int
  • a variable named val of type item
  • a constant named val of type Number
  • a variable named val of type Int

Q19. What is the error in this code?

extension String {
  var firstLetter: Character = "c" {
    didSet {
      print("new value")
    }
  }
}
  • Extensions can’t add properties. // although extensions technically can’t contain stored properties
  • Nothing is wrong with it.
  • didSet takes a parameter.
  • c is not a character.

Q20. didSet and willSet are examples of _?

  • property observers
  • key properties
  • all of these answers
  • newOld value calls

Q21. What is wrong with this code?

self.callback = {
  self.attempts += 1
  self.downloadFailed()
}
  • Use of self inside the closure causes retain cycle.
  • You cannot assign a value to closure in this manner.
  • You need to define the type of closure explicitly.
  • There is nothing wrong with this code.

Q22. How many values does vals have after this code is executed?

var vals = Set<String> = ["4", "5", "6"]
vals.insert("5")
  • three
  • four
  • eight
  • This code contains an error.

Q23. How can you avoid a strong reference cycle in a closure?

  • Use a capture list to set class instances of weak or unowned.
  • You can’t, there will always be a danger of strong reference cycles inside a closure.
  • Initialize the closure as read-only.
  • Declare the closure variable as lazy.

Q24. What is wrong with this code?

if let s = String.init("some string") {
  print(s)
}
  • This String initializer does not return an optional.
  • String does not have an initializer that can take a String.
  • = is not a comparison.
  • Nothing is wrong with this code.

Q25. Which code snippet correctly creates a typealias closure?

  • typealias CustomClosure: () -> ()
  • typealias CustomClosure { () -> () }
  • typealias CustomClosure -> () -> ()
  • typealias CustomClosure -> () {}

Q26. How do you reference class members from within a class?

  • self
  • instance
  • class
  • this

Q27. All value types in Swift are _ under the hood?

  • structs
  • classes
  • optionals
  • generics

Q28. What is the correct way to add a value to this array?

var strings = [1, 2, 3]
  • all of these answers
  • strings.append(4)
  • strings.insert(5, at: 1)
  • strings += [5]

Q29. How many times will this loop be executed?

for i in 0...100 {
  print(i)
}
  • 0
  • 101
  • 99
  • 100

Q30. What can AnyObject represent?

  • an instance of any class
  • an instance of function type
  • all of these answers
  • an instance of an optional type

Q31. What does this code print?

typealias Thing = [String:Any]
var stuff : Thing
print(type(of:stuff))
  • Dictionary
  • ERROR
  • Thing
  • Dictionary<String, Any>

Q32. What is the value of t after this code is executed?

let names = ["Larry", "Sven", "Bear"]
let t = names.enumerated().first().offset
  • This code is invalid.
  • This code does not compile.
  • 0
  • 1
  • Larry

Q32. What is the value of test after this code executes?

let vt = (name: "ABC", val: 5)
let test = vt.0
  • ABC
  • 0
  • 5
  • name

Q33. What is the base class in this code?

class LSN : MMM {
}
  • MMM
  • LSN
  • There is no base class.
  • This code is invalid.

Q34. What does this code print to the console?

var userLocation: String = "Home" {
  willSet(newValue) {
  print("About to set userLocation to \(newValue)...")
  }

  didSet {
  if userLocation != oldValue {
  print("userLocation updated with new value!")
  } else {
  print("userLocation already set to that value...")
  }
  }
 }

 userLocation = "Work"
  • About to set userLocation to Work… userLocation updated with new value!
  • About to set userLocation to Work… userLocation already set to that value…
  • About to set userLocation to Home… userLocation updated to new value!
  • ERROR

Q35. What must a convenience initializer call?

  • a base class convenience initializer
  • either a designated or another convenience initializer
  • a designated initializer
  • none of these answers

Q36. Which object allows you access to specify that a block of code runs in a background thread?

  • DispatchQueue.visible
  • DispatchQueue.global
  • errorExample need to be labeled as throws.
  • DispatchQueue.background

Q37. What is the inferred type of x?

let x = ["a", "b", "c"]
  • String[]
  • Array<String>
  • Set<String>
  • Array<Character>

Q38. What is the value of oThings after this code is executed?

let nThings: [Any] = [1, "2", "three"]
let oThings = nThings.reduce("") { "\($0)\($1)" }
  • 11212three
  • 115
  • 12three
  • Nothing, this code is invalid.

Q39. How would you call a function that throws errors and also returns a value?

  • !try
  • try?
  • try!
  • ?try

Q40. What is wrong with this code?

protocol TUI {
  func add(x1 : Int, x2 : Int) -> Int {
    return x1 + x2
  }
}
  • Protocol functions cannot have return types.
  • Protocol functions cannot have implementations.
  • Nothing is wrong with it.
  • add is a reserved keyword.

Q41. In this code, what are wheels and doors examples of?

class Car {
  var wheels: Int = 4
  let doors = 4
}
  • class members
  • This code is invalid.
  • class fields
  • class properties

Q42. How do you designated a failable initializer?

  • You cannot
  • deinit
  • init?
  • init

Q43. What is printed when this code is executed?

let dbl = Double.init("5a")
print(dbl ?? ".asString()")
  • five
  • 5a
  • .asString()
  • 5

Q44. In the function below, what are this and toThat examples of?

func add(this x: Int, toThat y: Int)->{}
  • none of these answers
  • local terms
  • argument labels
  • parameters names

Q45. What is wrong with this code?

for (key, value) in [1: "one", 2: "two"]{
  print(key, value)
}
  • The interaction source is invalid
  • The interaction variable is invalid
  • There is nothing wrong with this code
  • The comma in the print is misplaced

Q46. Which of these choices is associated with unit testing?

  • XCTest
  • all of these answers
  • @testable
  • XCAssert

Q47. In the code below, what is width an example of?

class Square{
  var height: Int = 0
  var width : Int {
    return height
  }
}
  • This code contains error
  • a closure
  • a computed property
  • lazy loading

Q48. What data type is this an example of?

let vals = ("val", 1)
  • a dictionary
  • a tuple
  • an optional
  • This code contains error

Q49. What is wrong with this code?

var x = 5
x = 10.0
  • You cannot assign a Double to a variable of type Int
  • x is undefined
  • x is a constant
  • x has no type

Q50. What will this code print to the console?

var items = ["a":1, "b":2, "c":"test"] as [String: Any]
items["c"] = nil
print(items["c"] as Any)
  • Any
  • test
  • 1,2,3
  • nil

Q51. What is wrong with this code?

let val = 5.0 + 10
  • There is nothing wrong with this code
  • val is a constant and cannot be changed
  • 5.0 and 10 are different types
  • There is no semicolon

Q52. How many parameters does the initializer for Test have?

struct Test{
  var score: Int
  var date: Date
}
  • zero
  • This code contains an error
  • two
  • Structs do not have initializers

Q53. What prints to the console when executing this code?

let x = try? String.init("test")
print(x)
  • nil
  • Nothing - this code contains an error
  • Optional(“test”)
  • test

Q54. How can you sort this array?

var vals = [1,2,3]
  • vals.sort { $0 < $1 }
  • vals.sort { (s1, s2) in s1 < s2 }
  • vals.sort(by: <)
  • all of these answers

Q55. DispatchQueue.main.async takes a block that will be

  • not executed
  • executed in the main queue
  • none of these answers
  • executed on the background thread

Q56. When is deinit called?

  • When a class instance needs memory
  • All of these answers
  • When the executable code is finished
  • When a class instance is being removed from memory

Q57. How do you declare an optional String?

  • String?
  • Optional[String]
  • [String]?
  • ?String

Q58. How many times this code will be executed? —OR— How many times will this loop be performed?

for i in ["0", "1"]{
  print(i)
}
  • one
  • two
  • three
  • This code does not compile

Q59. What does this code print?

let names = ["Bear", "Tony", "Svante"]
print(names[1]+"Bear")
  • 1Bear
  • BearBear
  • TonyBear
  • Nothing, this code is invalid

Q60. What is true of this code?

let name: String?
  • name can hold only a string value.
  • name can hold either a string or nil value.
  • Optional values cannot be let constants.
  • Only non-empty string variables can be stored in name.

Q61. What is the value of val after this code is executed?

let i = 5
let val = i * 6.0
  • This code is invalid.
  • 6
  • 30
  • 0

Q62. What does this code print?

enum Positions : Int {
  case first, second, third, other
}
print (Positions.other.rawValue)
  • 3
  • 0
  • other
  • nil

Q63. What is printed to the console when this code is executed?

"t".forEach { (char) in
    print(char)
}
  • nil
  • Nothing, since the code contains an error
  • t
  • zero

Q64. What prints when this code is executed?

let s1 = ["1", "2", "3"]
    .filter { $0 > "0" }
    .sorted { $0 > $1 }
print(s1)
  • []
  • [“3”, “2”, “1”]
  • [321]
  • [“1”, “2”, “3”]

Q65. What enumeration feature allows them to store case-specific data?

(Question does not make that much sense though. )

  • associated values
  • integral values
  • raw values
  • custom values

Q66. In the code below, AOM must be a(n)?

class AmP : MMM, AOM {
}
  • class
  • protocol
  • enumeration
  • struct

Q67. What is the value of numbers in the code below?

let numbers = [1,2,3,4,5,6].filter{ $0 % 2 == 0}
  • [1,3,5]
  • []
  • [2,4,6]
  • nil

Hope you like this!

Keep helping and happy 😄 coding

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