Swift MCQ Questions Answers

1. How can you extract val to x in tuple vt? let vt = (name: "ABC", val: 5)

2. What is the type of vals in this code? let vals = ["a", 1, "Hi"]

3. What is the value of numbers in the code below? let numbers = [1,2,3,4,5,6].filter{ $0 % 2 == 0}

4. In the code below, AOM must be a(n)? class AmP : MMM, AOM { }

5. What enumeration feature allows them to store case-specific data? (Question does not make that much sense though. )

6. What is printed to the console when this code is executed? "t".forEach { (char) in; print(char) }

7. What is the value of val after this code is executed? let i = 5; let val = i * 6.0

8. What is true of this code? let name: String?

9. What does this code print? let names = ["Bear", "Tony", "Svante"] print(names[1]+"Bear")

10. How many times this code will be executed? —OR— How many times will this loop be performed? for i in ["0", "1"]{print(i)}

11. How do you declare an optional String?

12. When is deinit called?

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

14. How can you sort this array?

15. What prints to the console when executing this code? let x = try? String.init("test") print(x)

16. What is wrong with this code? Let val = 5.0 + 10

17. What is wrong with this code? var x = 5; x = 10.0

18. What data type is this an example of? let vals = ("val", 1)

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

20. What is wrong with this code? for (key, value) in [1: "one", 2: "two"]{print(key, value)}

21. In the function below, what are this and toThat examples of? func add(this x: Int, toThat y: Int)->{}

22. How do you designated a failable initializer?

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

24. What is the inferred type of x? let x = ["a", "b", "c"]

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

26. What must a convenience initializer call?

27. What is the base class in this code? class LSN : MMM {}

28. What is the value of test after this code executes? let vt = (name: "ABC", val: 5) let test = vt.0

29. What is the value of t after this code is executed? let names = ["Larry", "Sven", "Bear"] let t = names.enumerated().first().offset

30. What can AnyObject represent?

31. How many times will this loop be executed? for i in 0...100 {print(i)}

32. What is the correct way to add a value to this array? var strings = [1, 2, 3]

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

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

35. Which code snippet correctly creates a typealias closure?

36. What is wrong with this code? if let s = String.init("some string") { print(s)}

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

38. How many values does vals have after this code is executed? var vals = Set = ["4", "5", "6"] vals.insert("5")

39. DidSet and willSet are examples of _?

40. What describes this line of code? let val = 5

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

42. What is the type of value1 in this code? let value1 = "\("test".count)"

43. The Codable protocol is _?

44. What is the correct way to call this function? func myFunc(_ a: Int, b: Int) -> Int {return a + b}

45. What is the type of this function? func add(a: Int, b: Int) -> Int { return a+b }

46. What is the value of y? var x: Int? let y = x ?? 5

47. What is the value of test in this code? var test = 1 == 1

48. What is the value of y? let x = ["1", "2"].dropFirst() let y = x[0]

49. What is this code an example of? let val = 5; print("value is: \(val)")

50. Why is dispatchGroup used in certain situations?

51. What is the raw/underlying type of this enum? enum Direction {case north, south, east, west}

52. What is the error in this code? let x = 5; guard x == 5 { return }

53. What is this code an example of? let val = (Double)6

54. Typical range of type Int8 is __

55. The following are unordered collection types:

56. A sequence of characters surrounded by double quotes is called _____?

57. Can cyclical relationships exist in value types?

58. A closure is a function without a name.

59. var varB = 3.14159ng is the c, varB is inferred to be of type _____

60. print(myStr) What will be the output of the above code snippet?

61. var myVar = 100 myVar = 'Hello World' print(varA) The output will be

62. We can create an array of any type

63. var tools: Set = ['Screwdriver', 'Pliers', 'Screwdriver'] var tools: Set = ['Screwdriver', 'Pliers', 'Screwdriver'] Which is correct?

64. Which is the correct naming scheme for an Objective-C bridging header file into Swift project

65. Bridging header file will not be compiled due to the following issues:

66. Objective-C class factory methods will change into _____ after importing to Swift

67. Overriding functionality is possible using extension

68. New initializers can be provided using extension

69. What is the correct way to import an Objective-C class into bridging header file?

70. enumerated() function iterates by __

71. The following are collection types in Swift

72. var myName: Int = 'John Doe' print(myName) The output will be

73. The 'let' keyword is considered as:

74. Create a new name for an existing type in Swift?

75. In Swift, private properties of a class can be accessed in any of it's extension.

76. Can you pass Int to a String type variable?

77. Serialize and archive your custom types in Swift?

78. Stage when memory returned to stack or heap?

79. During which stage memory is taken from stack or heap?

80. Deallocation never happens due to ___

81. What is the typical byte width of Float data type in Swift?

82. Weak references are declared as _____ types

83. unowned reference types are declared as __

84. 'NSOperationQueue.mainQueue().addOperationWithBlock' will add the operation to

85. GCD provides the following types of Queues:

86. NSOperationQueue conforms to

87. GCD can dispatch a task

88. func addStudent(_ student: Student) { concurrentStudentQueue.async(flags: .barrier) { self._students.append(student) DispatchQueue.main.async { // self.postContentAddedNotification() } } } The code will ensure that the submitted DispatchWorkItem will be executed in parallel with any other DispatchWorkItem in the same queue.

89. GCD conforms with the ____ order.

90. A Switch statement cannot handle String.

91. In which data types can you define methods?

92. Swift allows you to write semicolons at the end of statement.

93. If C is a superset of D, then D is a subset of C

94. Which is true about the Dictionary?

95. Extension can be used to create a new nested type of the following:

96. Instance methods can be _____ in extension

97. Which of the following are true about extension functionalities?

98. extension Int { subscript(var myInt: Int) -> Int { var no1 = 1 while myInt > 0 { no1 *= 10 --myInt } return (self / no1) % 10 } } print(12[0]) What is the output?

99. After importing Objective-C code to Swift, the above method will be imported as (instancetype)initWithFrame:(CGRect)frame style:(UITableViewStyle)style;

100. Objective-C class can be instantiated in Swift class only through