Respostas e perguntas sobre avaliação de habilidades do LinkedIn - Swift

“Rápido has emerged as a powerful and intuitive programming language for developing iOS, Mac OS, e aplicativos watchOS, oferecendo aos desenvolvedores uma plataforma moderna e eficiente para a construção de software inovador. Neste guia completo, we’re thrilled to present a series of skill assessment questions e respostas specifically tailored for Rápido Comercial.

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 Rápido and its applications. Join us as we explore the core concepts of Rápido programação, including optionals, closures, protocolos, e mais, empowering you to leverage the full potential of this essential tool for your iOS and macOS projects.”

T1. What is this code an example of?

let val = (Double)6

A syntax issue
Typecasting
Tarefa
Initialization

Referência: The Swift Programming Language: Language Guide: O básico: Constants and Variables

Q2. What is the error in this code?

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

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

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

3º T. What is the raw/underlying type of this enum?

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

There is none
String
Any
Int

Referência: 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.
Todas essas respostas.

Referência: Apple Developer: Documentação: Dispatch: Dispatch Group

Q5. What is this code an example of?

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

String interpolation
String compilation
Method chaining
Concatenação de strings

Referência: 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

Referência: Apple Developer: Documentations: Rápido: Variedade: organizar()

Q7. What does this code print?

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

Dictionary<String, Any>
Dictionary
Error
Thing

Referência: The Swift Programming Language: Language Reference: Tipos: 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

explicação
dropFirst() de 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.
Referência

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

var test = 1 == 1

true
YES
1
This code contains an error

Referência: 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

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

Q11. 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.

Referência: The Swift Programming Language: Language Guide: Funções: 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)

Referência: The Swift Programming Language: Language Guide: Funções: Function Argument Labels and Parameter Names

Q13. The Codable protocol is _?

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

Referências:

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

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

String
Int
null
test.count

Referência: 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
Todas essas respostas

Referência: 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.

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

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

Referência: The Swift Programming Language: Language Guide: O básico: 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.

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

Q20. didSet and willSet are examples of _?

Property observers
Key properties
Todas essas respostas
newOld value calls

Referência: The Swift Programming Language: Language Guide: Propriedades

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.

Referência: 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")

Três
Quatro
Eight
This code contains an error.

Referência: 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 ou 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.

Referência: 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)
}

este 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.

Referência: The Swift Programming Language: Language Guide: O básico: Optionals

Q25. Which code snippet correctly creates a typealias closure?

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

Referência: 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

Referência: The Swift Programming Language: Language Guide: Métodos: Instance Methods

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

Structs
Classes
Optionals
Generics

Referência: 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]

Todas essas respostas
strings.append(4)
strings.insert(5, at: 1)
strings += [5]

Referência: The Swift Programming Language: Language Guide: Collection Types: Matrizes

Q29. How many times will this loop be executed?

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

Referências:

Q30. What can AnyObject represent?

An instance of any class
An instance of function type
Todas essas respostas
An instance of an optional type

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

Q31. 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

Referências:

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

Referências:

Q33. What is the base class in this code?

class LSN: MMM {
}

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

Referência: The Swift Programming Language: Language Guide: Inheritance: Subclassing

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

Referência: The Swift Programming Language: Language Guide: Propriedades: Property Observers

Q35. What must a convenience initializer call?

A base class convenience initializer
Either a designated or another convenience initializer
A designated initializer
Nenhuma dessas respostas

Referência: 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

Referência: Apple Developer: Documentação: Dispatch: DispatchQueue

Q37. What is the inferred type of x?

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

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

Referência: The Swift Programming Language: Language Guide: Collection Types: Matrizes

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

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

11212três
115
12três
Nenhuma coisa, this code is invalid.

Referência: Apple Developer: Documentação: Rápido: Variedade: reduce(_:_:)

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

!try
try?
try!
?try

Referência: 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.

Referência:

Q41. In this code, o que são `wheels` e `doors` examples of?

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

Class members
This code is invalid
Class fields
Class properties

Referência:

Q42. How do you designated a failable initializer?

You cannot
deinit
init?
init

Referência:

Q43. What is printed when this code is executed?

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

five
5a
.asString()
5

Referência:

Q44. In the function below, o que são `this` e `toThat` examples of?

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

Nenhuma dessas respostas
Local terms
Argument labels
Parameters names

Referência: The Swift Programming Language: Language Guide: Funções

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

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

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

XCTest
Todas essas respostas
@testable
XCTAssert

Referência:

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

Referência:

Q48. What data type is this an example of?

let vals = ("val", 1)

Um dicionário
A tuple
An optional
This code contains error

Referência:

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

Referência: The Swift Programming Language: Language Guide: O básico

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)

Algum
teste
1,2,3
nil

Referências:

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 e 10 are different types
There is no semicolon

Referência: The Swift Programming Language: Language Guide: O básico: Type Safety and Type Inference

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

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

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

Referência: 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
Nenhuma coisa – this code contains an error
Opcional(“teste”)
teste

Referências:

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: <)
Todas essas respostas

Referência: Apple Developer: Documentação: Rápido: Variedade: organizar()

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

Not executed
Executed in the main queue
Nenhuma dessas respostas
Executed on the background thread

Referência: Apple Developer: Documentação: Dispatch: DispatchQueue: async(grupo:qos:flags:executar:)

Q56. When is deinit called?

When a class instance needs memory
Todas essas respostas
When the executable code is finished
When a class instance is being removed from memory

Referência: The Swift Programming Language: Language Guide: Deinitialization

Q57. How do you declare an optional String?

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

Referência: The Swift Programming Language: Language Guide: O básico: 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)
}

1
Dois
Três
This code does not compile

Referência: 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
Nenhuma coisa, this code is invalid

Referências:

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

Referência: The Swift Programming Language: Language Guide: O básico: 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

Referência: The Swift Programming Language: Language Guide: O básico: 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
de outros
nil

Referência: The Swift Programming Language: Language Guide: O básico: Raw Values

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

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

nil
Nenhuma coisa, since the code contains an error
t
zero

Referências:

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”]

Referências:

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

Associated values
Integral values
Raw values
Custom values

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

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

class AmP: MMM, AOM { }

Aula
Protocol
Enumeration
Struct

Referências:

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

Referência: Apple Developer: Documentação: Rápido: Swift Standard Library: Collections: Sequence and Collection Protocols: Seqüência: filtro()

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

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

Variedade(char)
[Algum]
Variedade
[Generic]

Referência: 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
Todas essas respostas
let x = vt.val
deixar (_, X) = vt

Referência: The Swift Programming Language: Language Guide: O básico: Tuples

Q70. What is the type of x?

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

Corda
Corda?
Corda!
tentar?

Referência: 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

Referência: 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
Três
Quatro

Referência: 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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