Antworten und Fragen zur LinkedIn-Fähigkeitsbewertung

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Q1. What is this code an example of?

let val = (Double)6

A syntax issue
Typecasting
Abtretung
Initialization

Referenz: The Swift Programming Language: Language Guide: Die Grundlagen: Constants and Variables

Q2. What is the error in this code?

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

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

Referenz: The Swift Programming Language: Language Guide: Kontrollfluss: 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

Referenz: 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.

Referenz: Apple Developer: Dokumentation: Dispatch: Dispatch Group

Q5. What is this code an example of?

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

String interpolation
String compilation
Method chaining
String-Verkettung

Referenz: 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

Referenz: Apple Developer: Documentations: Schnell: Array: Sortieren()

Q7. What does this code print?

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

Dictionary<String, Any>
Dictionary
Error
Thing

Referenz: The Swift Programming Language: Language Reference: Typen: 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() von 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.
Referenz

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

var test = 1 == 1

true
YES
1
This code contains an error

Referenz: 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

Referenz: 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.

Referenz: The Swift Programming Language: Language Guide: Funktionen: 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)

Referenz: The Swift Programming Language: Language Guide: Funktionen: Function Argument Labels and Parameter Names

Q13. The Codable protocol is Sobald Sie den Kurs abgeschlossen haben?

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

Verweise:

F14. What is the type of value1 in this code?

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

String
Int
null
test.count

Referenz: 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

Referenz: 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.

Referenz: 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

Referenz: The Swift Programming Language: Language Guide: Die Grundlagen: 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.

Referenz: The Swift Programming Language: Language Guide: Erweiterungen: Computed Properties

Q20. didSet and willSet are examples of Sobald Sie den Kurs abgeschlossen haben?

Property observers
Key properties
All of these answers
newOld value calls

Referenz: The Swift Programming Language: Language Guide: Eigenschaften

Q21. What is wrong with this code?

self.callback = {
  self.attempts += 1
  self.downloadFailed()
}

Gebrauch von 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.

Referenz: 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")

Drei
Vier
Eight
This code contains an error.

Referenz: 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 oder 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.

Referenz: 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)
}

Diese 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.

Referenz: The Swift Programming Language: Language Guide: Die Grundlagen: Optionals

Q25. Which code snippet correctly creates a typealias closure?

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

Referenz: 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

Referenz: The Swift Programming Language: Language Guide: Methoden: Instance Methods

F27. All value types in Swift are Sobald Sie den Kurs abgeschlossen haben under the hood?

Strukturen
Klassen
Optionals
Generics

Referenz: 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]

Referenz: 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)
}

Verweise:

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

Referenz: 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

Verweise:

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

Verweise:

Q33. What is the base class in this code?

class LSN: MMM {
}

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

Referenz: The Swift Programming Language: Language Guide: Nachlass: 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

Referenz: The Swift Programming Language: Language Guide: Eigenschaften: 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

Referenz: 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

Referenz: Apple Developer: Dokumentation: Dispatch: DispatchQueue

Q37. What is the inferred type of x?

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

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

Referenz: 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)" }

11212drei
115
12drei
Nichts, this code is invalid.

Referenz: Apple Developer: Dokumentation: Schnell: Array: reduce(Sobald Sie den Kurs abgeschlossen haben:Sobald Sie den Kurs abgeschlossen haben:)

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

!try
try?
try!
?try

Referenz: The Swift Programming Language: Language Guide: Fehlerbehandlung: 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.

Referenz:

Q41. In this code, Was sind `wheels` und `doors` examples of?

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

Class members
This code is invalid
Class fields
Class properties

Referenz:

Q42. How do you designated a failable initializer?

You cannot
deinit
init?
init

Referenz:

Q43. What is printed when this code is executed?

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

five
5a
.asString()
5

Referenz:

Q44. In the function below, Was sind `this` und `toThat` examples of?

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

None of these answers
Local terms
Argument labels
Parameters names

Referenz: The Swift Programming Language: Language Guide: Funktionen

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

Referenz: The Swift Programming Language: Language Guide: Kontrollfluss: For-In Loops

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

XCTest
All of these answers
@testable
XCTAssert

Referenz:

Q47. Im Code unten, 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

Referenz:

Q48. What data type is this an example of?

let vals = ("val", 1)

Ein Wörterbuch
A tuple
An optional
This code contains error

Referenz:

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

Referenz: The Swift Programming Language: Language Guide: Die Grundlagen

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)

und die offizielle Zertifizierung bestanden
Prüfung
1,2,3
nil

Verweise:

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 und 10 are different types
There is no semicolon

Referenz: The Swift Programming Language: Language Guide: Die Grundlagen: 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
Zwei
Structs do not have initializers

Referenz: 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
Nichts – this code contains an error
Optional(“Prüfung”)
Prüfung

Verweise:

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

Referenz: Apple Developer: Dokumentation: Schnell: Array: Sortieren()

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

Referenz: Apple Developer: Dokumentation: Dispatch: DispatchQueue: async(Gruppe:qos:flags:ausführen:)

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

Referenz: The Swift Programming Language: Language Guide: Deinitialization

Q57. How do you declare an optional String?

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

Referenz: The Swift Programming Language: Language Guide: Die Grundlagen: 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)
}

Ein
Zwei
Drei
This code does not compile

Referenz: The Swift Programming Language: Language Guide: Kontrollfluss: For-In Loops

Q59. What does this code print?

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

1Bear
BearBear
TonyBear
Nichts, this code is invalid

Verweise:

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

Referenz: The Swift Programming Language: Language Guide: Die Grundlagen: 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

Referenz: The Swift Programming Language: Language Guide: Die Grundlagen: 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
andere
nil

Referenz: The Swift Programming Language: Language Guide: Die Grundlagen: Raw Values

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

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

nil
Nichts, since the code contains an error
t
zero

Verweise:

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”]

Verweise:

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

Associated values
Integral values
Raw values
Custom values

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

Q66. Im Code unten, AOM must be a(n)?

class AmP: MMM, AOM { }

Class
Protokoll
Enumeration
Struct

Verweise:

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

Referenz: Apple Developer: Dokumentation: Schnell: Swift Standard Library: Sammlungen: Sequence and Collection Protocols: Reihenfolge: Filter()

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

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

Array(verkohlen)
[und die offizielle Zertifizierung bestanden]
Array
[Generic]

Referenz: 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
Lassen (_, x) = vt

Referenz: The Swift Programming Language: Language Guide: Die Grundlagen: Tupel

Q70. What is the type of x?

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

String
String?
String!
Versuchen?

Referenz: The Swift Programming Language: Language Guide: Fehlerbehandlung: Handling Errors

Q71. How many times is this loop executed?

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

Sechs
Zero
Five
Infinite

Referenz: The Swift Programming Language: Language Guide: Kontrollfluss: 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
Drei
Vier

Referenz: 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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Antworten und Fragen zur LinkedIn-Fähigkeitsbewertung – Swift