Swift

Questions and Answers

• What is this code an example of?
  1. a syntax issue
  2. typecasting
  3. assignment
  4. initialization
• What is the error in this code?
  1. The guard is missing the else.
  2. Nothing is wrong.
  3. The guard is missing a then.
  4. The comparison is wrong.
• What is the raw/underlying type of this enum?
  1. There is none.
  2. String
  3. Any
  4. Int
• Why is dispatchGroup used in certain situations?
  1. It allows multiple synchronous or asynchronous operations to run on different queues.
  2. It allows track and control execution of multiple operations together.
  3. It allows operations to wait for each other as desired.
  4. all of these answers.
• What is this code an example of?
  1. string interpolation
  2. string compilation
  3. method chaining
  4. string concatenation
• What are the contents of `vals` after this code is executed?
  1. [10, 2]
  2. [2, 10]
  3. nil
  4. This code contains an error
• What does this code print?
  1. Dictionary
  2. Dictionary
  3. ERROR
  4. Thing
• What is the value of y?
  1. This code contains an error
  2. 1
  3. 2
  4. nil
• What is the value of test in this code?
  1. TRUE
  2. YES
  3. 1
  4. This code contains an error
• What is the value of y?
  1. 5
  2. 0
  3. nil
  4. This code contains an error
• What is the type of this function?
  1. Int
  2. (Int, Int) -> Int
  3. Int
  4. Functions don't have types.
• What is the correct way to call this function?
  1. myFunc(5, b: 6)
  2. myFunc(5, 6)
  3. myFunc(a: 5, b: 6)
  4. myFunc(a, b)
• The Codable protocol is **\_**?
  1. a combination of Encodable and Decodable
  2. not a true protocol <<<<---Possibly correct as it's a typealias of Encodable and Decodable
  3. required of all classes
  4. automatically included in all classes
• What is the type of value1 in this code?
  1. String
  2. Int
  3. null
  4. test.count
• When a function takes a closure as a parameter, when do you want to mark is as escaping?
  1. when it's executed after the function returns
  2. when it's scope is undefined
  3. when it's lazy loaded
  4. all of these answers
• What's wrong with this code?
  1. Person has no initializers.
  2. Person has no base class.
  3. var name is not formatted corrrectly.
  4. address is a keyword.
• What is the value of names after this code is executed?
  1. ["BEAR", "JOE", "CLARK"]
  2. ["B", "J", "C"]
  3. ["Bear", "Joe", "Clark"]
  4. This code contains an error.
• What describes this line of code?
  1. a constant named val of type Int
  2. a variable named val of type item
  3. a constant named val of type Number
  4. a variable named val of type Int
• What is the error in this code?
  1. Extensions can't add properties. // although extensions technically can't contain stored properties
  2. Nothing is wrong with it.
  3. didSet takes a parameter.
  4. c is not a character.
• didSet and willSet are examples of **\_**?
  1. property observers
  2. key properties
  3. all of these answers
  4. newOld value calls
• What is wrong with this code?
  1. Use of self inside the closure causes retain cycle.
  2. You cannot assign a value to closure in this manner.
  3. You need to define the type of closure explicitly.
  4. There is nothing wrong with this code.
• How many values does vals have after this code is executed?
  1. three
  2. four
  3. eight
  4. This code contains an error.
• How can you avoid a strong reference cycle in a closure?
  1. Use a capture list to set class instances of weak or unowned.
  2. You can't, there will always be a danger of strong reference cycles inside a closure.
  3. Initialize the closure as read-only.
  4. Declare the closure variable as lazy.
• What is wrong with this code?
  1. This String initializer does not return an optional.
  2. String does not have an initializer that can take a String.
  3. = is not a comparison.
  4. Nothing is wrong with this code.
• Which code snippet correctly creates a typealias closure?
  1. typealias CustomClosure: () -> ()
  2. typealias CustomClosure { () -> () }
  3. typealias CustomClosure -> () -> ()
  4. typealias CustomClosure -> () {}
• How do you reference class members from within a class?
  1. self
  2. instance
  3. class
  4. this
• All value types in Swift are **\_** under the hood?
  1. structs
  2. classes
  3. optionals
  4. generics
• What is the correct way to add a value to this array?
  1. all of these answers
  2. strings.append(4)
  3. strings.insert(5, at: 1)
  4. strings += [5]
• How many times will this loop be executed?
  1. 0
  2. 101
  3. 99
  4. 100
• What can AnyObject represent?
  1. an instance of any class
  2. an instance of function type
  3. all of these answers
  4. an instance of an optional type
• What is the value of t after this code is executed?
  1. This code is invalid.
  2. This code does not compile.
  3. 0
  4. 1
• What is the value of test after this code executes?
  1. ABC
  2. 0
  3. 5
  4. name
• What is the base class in this code?
  1. MMM
  2. LSN
  3. There is no base class.
  4. This code is invalid.
• What does this code print to the console?
  1. About to set userLocation to Work? userLocation updated with new value!
  2. About to set userLocation to Work? userLocation already set to that value?
  3. About to set userLocation to Home? userLocation updated to new value!
  4. ERROR
• What must a convenience initializer call?
  1. a base class convenience initializer
  2. either a designated or another convenience initializer
  3. a designated initializer
  4. none of these answers
• Which object allows you access to specify that a block of code runs in a background thread?
  1. DispatchQueue.visible
  2. DispatchQueue.global
  3. errorExample need to be labeled as `throws`.
  4. DispatchQueue.background
• What is the inferred type of x?
  1. `String[]`
  2. `Array`
  3. `Set`
  4. `Array`
• What is the value of `oThings` after this code is executed?
  1. 11212three
  2. 115
  3. 12three
  4. Nothing, this code is invalid.
• How would you call a function that throws errors and also returns a value?
  1. `!try`
  2. `try?`
  3. `try!`
  4. `?try`
• What is wrong with this code?
  1. Protocol functions cannot have return types.
  2. Protocol functions cannot have implementations.
  3. Nothing is wrong with it.
  4. `add` is a reserved keyword.
• In this code, what are `wheels` and `doors` examples of?
  1. class members
  2. This code is invalid.
  3. class fields
  4. class properties
• How do you designated a failable initializer?
  1. You cannot
  2. deinit
  3. `init?`
  4. init
• What is printed when this code is executed?
  1. five
  2. 5a
  3. `.asString()`
  4. 5
• In the function below, what are `this` and `toThat` examples of?
  1. none of these answers
  2. local terms
  3. argument labels
  4. parameters names
• What is wrong with this code?
  1. The interaction source is invalid
  2. The interaction variable is invalid
  3. There is nothing wrong with this code
  4. The comma in the print is misplaced
• Which of these choices is associated with unit testing?
  1. XCTest
  2. all of these answers
  3. @testable
  4. XCAssert
• In the code below, what is width an example of?
  1. This code contains error
  2. a closure
  3. a computed property
  4. lazy loading
• What data type is this an example of?
  1. a dictionary
  2. a tuple
  3. an optional
  4. This code contains error
• What is wrong with this code?
  1. You cannot assign a Double to a variable of type Int
  2. x is undefined
  3. x is a constant
  4. x has no type
• What will this code print to the console?
  1. Any
  2. test
  3. 1,2,3
  4. nil
• What is wrong with this code?
  1. There is nothing wrong with this code
  2. val is a constant and cannot be changed
  3. 5.0 and 10 are different types
  4. There is no semicolon
• How many parameters does the initializer for Test have?
  1. zero
  2. This code contains an error
  3. two
  4. Structs do not have initializers
• What prints to the console when executing this code?
  1. nil
  2. Nothing - this code contains an error
  3. Optional("test")
  4. test
• How can you sort this array?
  1. `vals.sort { $0 < $1 }`
  2. `vals.sort { (s1, s2) in s1 < s2 }`
  3. `vals.sort(by: <)`
  4. all of these answers
• DispatchQueue.main.async takes a block that will be
  1. not executed
  2. executed in the main queue
  3. none of these answers
  4. executed on the background thread
• When is deinit called?
  1. When a class instance needs memory
  2. All of these answers
  3. When the executable code is finished
  4. When a class instance is being removed from memory
• How do you declare an optional String?
  1. String?
  2. Optional[String]
  3. [String]?
  4. ?String
• How many times this code will be executed? ?OR? How many times will this loop be performed?
  1. one
  2. two
  3. three
  4. This code does not compile
• What does this code print?
  1. 1Bear
  2. BearBear
  3. TonyBear
  4. Nothing, this code is invalid
• What is true of this code?
  1. name can hold only a string value.
  2. name can hold either a string or nil value.
  3. Optional values cannot be `let` constants.
  4. Only non-empty string variables can be stored in name.
• What is the value of `val` after this code is executed?
  1. This code is invalid.
  2. 6
  3. 30
  4. 0
• What does this code print?
  1. 3
  2. 0
  3. other
  4. nil
• What is printed to the console when this code is executed?
  1. nil
  2. Nothing, since the code contains an error
  3. t
  4. zero
• What prints when this code is executed?
  1. []
  2. ["3", "2", "1"]
  3. [321]
  4. ["1", "2", "3"]
• What enumeration feature allows them to store case-specific data?
  1. associated values
  2. integral values
  3. raw values
  4. custom values
• In the code below, AOM must be a(n)?
  1. class
  2. protocol
  3. enumeration
  4. struct
• What is the value of numbers in the code below?
  1. [1,3,5]
  2. []
  3. [2,4,6]
  4. nil
• What is the type of `vals` in this code?
  1. Array(char)
  2. [Any]
  3. Array
  4. [Generic]
• How can you extract val to `x` in tuple `vt`
  1. let x = vt.1
  2. all of these answers
  3. let x = vt.val
  4. let (`_`, x) = vt