Swift Test Answers
·
1. What is the name of the Xcode
generated header file used to import Swift classes into an Objective-C Class
given a product module named Example?
Answers:
• ExampleSwift.h
• Example.Swift.h
• Example+Swift.h
• Example-Swift.h
2. What does a retainCount represent
in ARC?
Answers:
• The current
number of strong references to an object.
• The current
number of instances of an object.
• The total
number of objects currently being retained in memory.
• The total number of times an object
has been allocated.
3. Which of these statements is a
valid way to extend the capabilities of our theoretical class, MyClass to
conform to protocol MyProtocol?
Answers:
• extension
MyClass(MyProtocol) { }
• extension
MyClass, prot MyProtocol { }
• extension MyClass: MyProtocol { }
• extension
MyClass, MyProtocol { }
4. Which one is the correct keyword
for defining a constant in Swift?
Answers:
• const
• contant
• final
• let
• def
5. What is the output of this segment
of code ?
var x = 0
for index in 1...5 {
++x
}
println("\(x)")
Answers:
• 0
• compile error
• 5
• 4
6. Which one of the below functions
definitions is wrong considering Swift language?
Answers:
• func
haveChar(#string: String, character: Character) -> (Bool)
• func mean(numbers: Double...)
-> Double
• func
minMax(array: [Int]) -> (min: Int, max: Int)?
• func
minMax(array: [Int]) -> (min: Int?, max: Int?)
7. Which of these is a valid syntax
for iterating through the keys and values of a dictionary?
let dictionary = [keyOne : valueOne,
keyTwo : valueTwo]
Answers:
• for (key, value) in dictionary {
println("Key: \(key) Value: \(value)") }
• for (key,
value) in enumerate(dictionary) { println("Key: \(key) Value:
\(value)") }
• for (key,
value) in (dictionary.keys, dictionary.values) { println("Key: \(key)
Value: \(value)") }
• for (key,
value) in dictionary.enumerate() { println("Key: \(key) Value:
\(value)") }
8. What is the name of the Swift
language feature that Objective-C Blocks are translated into?
Answers:
• Lambda
• Callback
• Closure
• Selector
9. Which one creates a dictionary with
a key type of Integer and value of String?
Answers:
• var dict:[Int:
String] = ["one":1]
• var dict: [Int: String] =
[1:"one"]
• var dict:
[String: Int] = [1:"one"]
• var dict =
["one":1]
10. Which of these is an appropriate
syntax for dispatching a heavy operation to a background thread?
Answers:
•
dispatch_async(DISPATCH_QUEUE_PRIORITY_BACKGROUND), { self.heavyOperation() })
•
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND,
0), { self.heavyOperation() })
•
DISPATCH_QUEUE_PRIORITY_BACKGROUND({ self.heavyOperation() })
•
dispatch_async({ self.heavyOperation() })
11. What is the name of the
deinitializer in a Class declaration?
Answers:
• deinit
• dealloc
• release
12. Which of these is an appropriate
syntax for declaring a function that takes an argument of a generic type?
Answers:
• func
genericFunction(argument: T<Generic>) { }
• func
genericFunction<T>(argument) { }
• generic func
genericFunction(argument: T) { }
• func
genericFunction<T>(argument: T) { }
13. Which of these is not a valid
property declaration in Swift?
Answers:
• final let x = 0
• final lazy let x = 0
• final lazy var
x = 0
• final var x = 0
14. Which is the wrong
definition of a protocol in Swift?
Answers:
• protocol SomeProtocol { var first:
Int{ get } }
• protocol
SomeProtocol { var first: Int{ set } }
• protocol
SomeProtocol { var first: Int { get set } }
• protocol SomeProtocol
{ var first: Int { get set } var second: Int { get } }
15. Which of the following structures
has both computed and stored properties?
Answers:
• struct Rect { var origin =
CGPointZero var center: CGPoint { get { // } set { // } } }
• struct Rect {
var center: CGPoint { get { // } set { // } } }
• struct Rect {
let origin = CGPointZero }
• struct Rect {
var origin = CGPointZero var center: CGPointMake(0,0) }
16. Considering var index = UInt8.max,
which of the following operation results to the value of zero for var index?
Answers:
• index = index
&- 1
• index = index &+ 1
• index = index
&* 1
• index = index
&/ 255
17. All Swift classes must inherit
from which root class?
Answers:
• Swift classes do not require a
root class.
• NSObject
• @ObjC
• Root
18. Which keyword is used on a
function in an enumeration to indicate that the function will modify 'self'?
Answers:
• modifier
• mutating
• mutable
• mod
• mut
19. Which is correct for Enumerations?
Answers:
• Enumerations can define
initializers.
• Enumerations
cannot conform to protocols.
• Enumerations
cannot conform to protocols.
20. Which of these is a valid
definition of a generic function that incorporates inout parameters in Swift?
Answers:
• func swap<T>(inout a: T,
inout b: T) { let temp = a a = b b = temp }
• func
swap<U,T>(inout a: U, inout b: T) { let temp = a a = b b = temp }
• func
swap<U,T>( a: U, b: T) { let temp = a a = b b = temp }
• func
swap<T>( a: T, b: T) { let temp = a a = b b = temp }
21. If we have a class named MyClass
with a nested enum called Status, declared like so:
class MyClass {
enum Status {
case On, Off
}
}
How would one indicate that a variable
is an enum of type Status outside the context of MyClass?
Answers:
• var status: MyClass.Status = .On
• var status:
Status = .On
• var status:
MyClass<Status> = .On
• var status:
MyClass(Status) = .On
22. Which of the following could be
used to indicate the Function Type of the following function:
func joinStrings(stringOne: String,
stringTwo: String) -> String {
return stringOne +
stringTwo
}
Answers:
• func(String,
String -> String)
• (String, String) -> String
• {String,
String} -> String
• {String,
String}(String)
23. Which of the following statements
could be used to determine if a given variable is of String type?
Answers:
• if
String.hierarchy(unknownVariable) { }
• if unknownVariable is String { }
• if
unkownVariable: String { }
• if
(String)unknownVariable { }
24. Which of these could be an
appropriate protocol declaration in Swift?
Answers:
• @objc protocol someProtocal {
optional var first: Int { get } }
• @objc protocol
someProtocal { optional var first: Int { set } }
• protocol
someProtocal { optional var first: Int { get } }
• protocol
someProtocal { var first: Int { set } }
25. In context of a Swift subscript,
which of the following is correct?
Answers:
• struct MyStruct { var myStr =
[String]() subscript (index : Int) -> String{ get{ return myStr[index] }
set{ myStr[index] = newValue } } }
• struct MyStruct
{ var myStr = [String]() subscript (index : Int) -> Int{ get{ return
myStr[index] } set(newValue){ myStr[index] = newValue } } }
• struct MyStruct
{ var myStr = [String]() subscript (index : Int) -> String{ get(){ return
myStr[index] } set(newValue){ myStr[index] = newValue } } }
• struct MyStruct
{ var myStr = [String] subscript (index : Int) -> String{ get(){ return
myStr[index] } set(newValue){ myStr[index] = newValue } } }
26. What is used to import Objective-C
files into Swift?
Answers:
• Objective-C classes are
automatically imported.
• Objective-C
classes are imported in the Swift file using the class.
• Objective-C
classes are imported via a Bridging Header.
• Objective-C
classes import themselves by declare @SwiftImportable.
27. What keyword is used to indicate a
custom operator that will appear in between two targets, similar to the
addition operator in this example?
var sum = 10 + 10
Answers:
• @inter
• between
• infix
• @center
28. Which is correct regarding Swift
enumeration members when they are defined?
Answers:
• Members are assigned a default
integer value.
• Members are
assigned a random default integer value.
• Members are not
assigned default integer values.
29. What type of object are Swift
Structures?
Answers:
• Reference Type
• Memory Type
• Abstract Type
• Value Type
30. Which keyword in the context of a
Switch statement is required to force the execution of a subsequent case?
Answers:
• fallthrough
• continue
• break
• return
31. What is the type of Swift
Enumerations?
Answers:
• Reference type
• Class type
• Collection type
• Value type
32. Given that we have defined myChar
like so :
let myChar: Character = "b"
Which code segment can be considered a
complete Switch statement and will run without any error?
Answers:
• switch myChar {
case "a","A": println("The letter A") case
"b","B": println("The letter A") }
• switch myChar { case
"a": println("The letter A") }
• switch myChar {
case "a": case "A": println("The letter A") default:
println("Not the letter A") }
• switch myChar {
case "a","A": println("The letter A") default:
println("Not the letter A") }
33. Can enumeration type have methods?
Answers:
• Enumerations can have methods
associate with them.
• Enumerations
can have only member values.
34. Which of the following declares a
mutable array in Swift?
Answers:
• var x = [Int]
• let x = [Int]
• var x = [Int]()
• let x = [Int]()
35. Which keyword is used in Swift
when we want a property of a class to initialize when it is accessed for the
first time?
Answers:
• let
• var
• const
• lazy
36. Which is used for down casting?
Answers:
• as!
• is
• is?
• as?
37. What attribute can be used to
allow a protocol to contain optional functions and to be used in ObjC?
Answers:
• objective_bridge
• ObjC
• _objc
• @objc
38. Which of the following types can
be used use as raw value types for an enumeration?
Answers:
• Bool
• Array
• Int, String, Float
• Dictionary
39. Which keyword do you use to
declare enumeration?
Answers:
• var
• enum
• struct
• case
40. When declaring an enumeration,
multiple member values can appear on a single line, separated by which
punctuation mark?
Answers:
• Semi-colon
• Colon
• Comma
• Slash
• Point
