LinkedIn skill assessment answers and questions — Swift

“Swift has emerged as a powerful and intuitive programming language for developing iOS, ระบบปฏิบัติการ macOS, and watchOS applications, offering developers a modern and efficient platform for building innovative software. ในคู่มือที่ครอบคลุมนี้, we’re thrilled to present a series of skill assessment questions และ คำตอบ specifically tailored for Swift ผู้ใช้.

Whether you’re a seasoned developer looking to expand your capabilities or a beginner aiming to understand the basics of this powerful language, this resource is designed to help you become proficient in Swift and its applications. Join us as we explore the core concepts of Swift การเขียนโปรแกรม, including optionals, closures, protocols, และอื่น ๆ, empowering you to leverage the full potential of this essential tool for your iOS and macOS projects.”

Q1. What is this code an example of?

let val = (Double)6

A syntax issue
Typecasting
Assignment
Initialization

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: The Basics: Constants and Variables

Q2. What is the error in this code?

let x = 5
guard x == 5 { return }

NS guard is missing the else
Nothing is wrong
NS guard is missing a then
The comparison is wrong

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Control Flow: Early Exit

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

enum Direction {
  case north, south, east, west
}

There is none
String
Any
Int

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Enumerations: Raw Values

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.

ถ้ามีออกซิเจนเพียงพอ: Apple Developer: เอกสาร: Dispatch: Dispatch Group

Q5. What is this code an example of?

let val = 5
print("value is: \(val)")

String interpolation
String compilation
Method chaining
การต่อสตริง

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Strings and Characters: String Interpolation

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

ถ้ามีออกซิเจนเพียงพอ: Apple Developer: Documentations: Swift: อาร์เรย์: เรียงลำดับ()

Q7. What does this code print?

typealias Thing = [String: Any]
var stuff: Thing
print(type(of: stuff))

Dictionary<String, Any>
Dictionary
Error
Thing

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Reference: Types: Type Identifier

Q8. What is the value of y?

let x = ["1", "2"].dropFirst()
let y = x[0]

This code contains an error
1
2
nil

explanation
dropFirst() จาก Swift.Collection.Array returns a type of ArraySlice<Element>
as in the documentation pages:
@inlinable public func dropFirst(_ k: Int = 1) -> ArraySlice<Element>

The ArraySlice type makes it fast and efficient for you to perform operations on sections of a larger array. Instead of copying over the elements of a slice to new storage, an ArraySlice instance presents a view onto the storage of a larger array. And because ArraySlice presents the same interface as Array, you can generally perform the same operations on a slice as you could on the original array.

Slices Maintain Indices
Unlike Array and ContiguousArray, the starting index for an ArraySlice instance isn’t always zero. Slices maintain the same indices of the larger array for the same elements, so the starting index of a slice depends on how it was created, letting you perform index-based operations on either a full array or a slice.
The above code returns a slice of value ["2"] but the index did not change. let y = x[1] would give the expected result.
To safely reference the starting and ending indices of a slice, always use the startIndex and endIndex properties instead of specific values.
ถ้ามีออกซิเจนเพียงพอ

คำถามที่ 9. What is the value of test in this code?

var test = 1 == 1

true
YES
1
This code contains an error

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Basic Operators: Comparison Operators

Q10. What is the value of y?

var x: Int?
let y = x ?? 5

5
0
nil
This code contains an error

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Basic Operators: Nil-Coalescing Operators

คำถามที่ 11. What is the type of this function?

func add(a: Int, b: Int) -> Int { return a+b }

Int
(Int, Int) -> Int
Int<Optional>
Functions don’t have types.

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: ฟังก์ชั่น: Function 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)

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: ฟังก์ชั่น: Function Argument Labels and Parameter Names

ไตรมาสที่ 13. The Codable protocol is _?

A combination of Encodable และ Decodable
Not a true protocol
Required of all classes
Automatically included in all classes

อ้างอิง:

คำถามที่ 14. What is the type of value1 in this code?

let value1 = "\("test".count)"

String
Int
null
test.count

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Strings and Characters: String Interpolation

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 it’s lazy loaded
All of these answers

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Closures: Escaping Closures

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 correctly.
address is a keyword.

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Initialization: Class Inheritance and Initialization

ไตรมาสที่ 17. 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

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: The Basics: Type Safety and Type Inference

Q19. What is the error in this code?

extension String {
  var firstLetter: Character = "c" {
    didSet {
      print("new value")
    }
  }
}

Extensions can’t add properties.
Nothing is wrong with it.
didSet takes a parameter.
c is not a character.

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Extensions: Computed Properties

ไตรมาสที่ 20. didSet and willSet are examples of _?

Property observers
Key properties
All of these answers
newOld value calls

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: คุณสมบัติ

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 a closure in this manner.
You need to define the type of closure explicitly.
There is nothing wrong with this code.

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Automatic Reference Counting: Strong Reference Cycles for Closures

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

var vals = Set<String> = ["4", "5", "6"]
vals.insert("5")

สาม
โฟร์
Eight
This code contains an error.

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Collection Types: Sets

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

Use a capture list to set class instances of weak หรือ 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.

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Automatic Reference Counting

Q24. What is wrong with this code?

if let s = String.init("some string") {
  print(s)
}

นี้ 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.

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: The Basics: Optionals

Q25. Which code snippet correctly creates a typealias closure?

typealias CustomClosure = () -> ()
typealias CustomClosure { () -> () }
typealias CustomClosure -> () -> ()
typealias CustomClosure -> () {}

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Reference: Declarations: Type Alias Declaration

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

self
instance
class
this

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: ทำความเข้าใจการรับสินค้าคงคลัง: Instance Methods

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

Structs
Classes
Optionals
Generics

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Structures and Classes

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]

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Collection Types: Arrays

Q29. How many times will this loop be executed?

for i in 0...100 {
  print(i)
}

อ้างอิง:

ไตรมาสที่ 30. What can AnyObject represent?

An instance of any class
An instance of function type
All of these answers
An instance of an optional type

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Type Casting: Type Casting for Any and AnyObject

ไตรมาสที่ 31. What is the value of t after this code is executed?

let names = ["Larry", "Sven", "Bear"]
let t = names.enumerated().first().offset

This code does not compile. / This code is invalid.
0
1
Larry

อ้างอิง:

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

อ้างอิง:

Q33. What is the base class in this code?

class LSN: MMM {
}

MMM
LSN
There is no base class.
This code is invalid.

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: มรดก: Subclassing

คำถามที่ 34. 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

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: คุณสมบัติ: Property Observers

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

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Initialization: Class Inheritance and Initialization

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

ถ้ามีออกซิเจนเพียงพอ: Apple Developer: เอกสาร: Dispatch: DispatchQueue

Q37. What is the inferred type of x?

let x = ["a", "b", "c"]

String[]
Array<String>
Set<String>
Array<Character>

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Collection Types: Arrays

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

let nThings: [Any] = [1, "2", "three"]
let oThings = nThings.reduce("") { "\($0)\($1)" }

11212สาม
115
12สาม
ไม่มีอะไร, this code is invalid.

ถ้ามีออกซิเจนเพียงพอ: Apple Developer: เอกสาร: Swift: อาร์เรย์: reduce(_:_:)

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

!try
try?
try!
?try

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Error Handling: Handling Errors

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.

ถ้ามีออกซิเจนเพียงพอ:

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

class Car {
  var wheels: Int = 4
  let doors = 4
}

Class members
This code is invalid
Class fields
Class properties

ถ้ามีออกซิเจนเพียงพอ:

Q42. How do you designated a failable initializer?

You cannot
deinit
init?
init

ถ้ามีออกซิเจนเพียงพอ:

Q43. What is printed when this code is executed?

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

five
5a
.asString()
5

ถ้ามีออกซิเจนเพียงพอ:

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

func add(this x: Int, toThat y: Int) { }

None of these answers
Local terms
Argument labels
Parameters names

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: ฟังก์ชั่น

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

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Control Flow: For-In Loops

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

XCTest
All of these answers
@testable
XCTAssert

ถ้ามีออกซิเจนเพียงพอ:

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

ถ้ามีออกซิเจนเพียงพอ:

Q48. What data type is this an example of?

let vals = ("val", 1)

พจนานุกรม
A tuple
An optional
This code contains error

ถ้ามีออกซิเจนเพียงพอ:

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

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: The Basics

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
ทดสอบ
1,2,3
nil

อ้างอิง:

คำถามที่ 51. 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 และ 10 are different types
There is no semicolon

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: The Basics: Type Safety and Type Inference

คำถามที่ 52. How many parameters does the initializer for Test have?

struct Test {
  var score: Int
  var date: Date
}

Zero
This code contains an error
สอง
Structs do not have initializers

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Initialization

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

let x = try? String.init("test")
print(x)

nil
ไม่มีอะไร – this code contains an error
ไม่จำเป็น(“ทดสอบ”)
ทดสอบ

อ้างอิง:

คำถามที่ 54. 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

ถ้ามีออกซิเจนเพียงพอ: Apple Developer: เอกสาร: Swift: อาร์เรย์: เรียงลำดับ()

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

ถ้ามีออกซิเจนเพียงพอ: Apple Developer: เอกสาร: Dispatch: DispatchQueue: async(กลุ่ม:qos:flags:ดำเนินการ:)

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

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Deinitialization

Q57. How do you declare an optional String?

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

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: The Basics: Optionals

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

for i in ["0", "1"] {
  print(i)
}

หนึ่ง
สอง
สาม
This code does not compile

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Control Flow: For-In Loops

Q59. What does this code print?

let names = ["Bear", "Tony", "Svante"]
print(names[1] + "Bear")

1Bear
BearBear
TonyBear
ไม่มีอะไร, this code is invalid

อ้างอิง:

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 ค่าคงที่.
Only non-empty string variables can be stored in name.

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: The Basics: Optionals

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

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: The Basics: Type Safety and Type Inference

Q62. What does this code print?

enum Positions: Int {
  case first, second, third, other
}

print (Positions.other.rawValue)

3
0
อื่น
nil

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: The Basics: Raw Values

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

"t".forEach { (char) in
  print(char)
}

nil
ไม่มีอะไร, since the code contains an error
ทำไม Tundra Biome จึงเป็น Biome ที่หนาวที่สุดในโลก
zero

อ้างอิง:

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”]

อ้างอิง:

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

Associated values
Integral values
Raw values
Custom values

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Enumerations: Associated Values

Q66. In the code below, AOM must be a(ทำไม Tundra Biome จึงเป็น Biome ที่หนาวที่สุดในโลก)?

class AmP: MMM, AOM { }

ระดับ
มาตรการ
Enumeration
Struct

อ้างอิง:

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

ถ้ามีออกซิเจนเพียงพอ: Apple Developer: เอกสาร: Swift: Swift Standard Library: Collections: Sequence and Collection Protocols: ลำดับ: กรอง()

Q68. What is the type of `vals` in this code?

let vals = ["a", 1, "Hi"]

อาร์เรย์(char)
[Any]
อาร์เรย์
[Generic]

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Type Casting

Q69. How can you extract val to `x` in tuple `vt`

let vt = (name: "ABC", val: 5)

let x = vt.1
All of these answers
let x = vt.val
อนุญาต (_, NS) = vt

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: The Basics: Tuples

Q70. What is the type of x?

let x = try? String.init(from: decoder)

String
String?
String!
try?

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Error Handling: Handling Errors

Q71. How many times is this loop executed?

let loopx = 5
repeat {
  print (loopx)
} while loopx < 6

Six
Zero
Five
Infinite

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Control Flow: While Loops

Q72. How many values does vals have after this code is executed?

var vals: Set<String> = ["4", "5", "6"]
vals.insert("5")

This code contains an error.
Eight
สาม
โฟร์

ถ้ามีออกซิเจนเพียงพอ: The Swift Programming Language: Language Guide: Collection Types: Sets

Q73. What is the base class in this code ?

class LSN: MMM{ }

MMM
LSN
There is no base class.
This code is invalid.

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LinkedIn skill assessment answers and questions — Swift