# What is this code an example of? ```swift let val = (Double)6 ``` - [x] a syntax issue - [ ] typecasting - [ ] assignment - [ ] initialization # What is the error in this code? ```swift let x = 5 guard x == 5 { return } ``` - [x] The guard is missing the else. - [ ] Nothing is wrong. - [ ] The guard is missing a then. - [ ] The comparison is wrong. # What is the raw/underlying type of this enum? ```swift enum Direction { case north, south, east, west } ``` - [x] There is none. - [ ] String - [ ] Any - [ ] Int # 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. - [x] all of these answers. # What is this code an example of? ```swift let val = 5 print("value is: \(val)") ``` - [x] string interpolation - [ ] string compilation - [ ] method chaining - [ ] string concatenation # What are the contents of `vals` after this code is executed? ```swift var vals = [10, 2] vals.sort { (s1, s2) -> Bool in s1 > s2 } ``` - [x] [10, 2] - [ ] [2, 10] - [ ] nil - [ ] This code contains an error # What does this code print? ```swift typealias Thing = [String:Any] var stuff: Thing print(type(of: stuff)) ``` - [x] Dictionary - [ ] Dictionary - [ ] ERROR - [ ] Thing # What is the value of y? ```swift let x = ["1", "2"].dropFirst() let y = x[0] ``` - [x] This code contains an error - [ ] 1 - [ ] 2 - [ ] nil # What is the value of test in this code? ```swift var test = 1 == 1 ``` - [x] TRUE - [ ] YES - [ ] 1 - [ ] This code contains an error # What is the value of y? ```swift var x: Int? let y = x ?? 5 ``` - [x] 5 - [ ] 0 - [ ] nil - [ ] This code contains an error # What is the type of this function? ```swift func add(a: Int, b: Int) -> Int { return a+b } ``` - [ ] Int - [x] (Int, Int) -> Int - [ ] Int - [ ] Functions don't have types. # What is the correct way to call this function? ```swift func myFunc(_ a: Int, b: Int) -> Int { return a + b } ``` - [x] myFunc(5, b: 6) - [ ] myFunc(5, 6) - [ ] myFunc(a: 5, b: 6) - [ ] myFunc(a, b) # The Codable protocol is **\_**? - [x] a combination of Encodable and Decodable - [ ] not a true protocol <<<<---Possibly correct as it's a typealias of Encodable and Decodable - [ ] required of all classes - [ ] automatically included in all classes # What is the type of value1 in this code? ```swift let value1 = "\("test".count)" ``` - [x] String - [ ] Int - [ ] null - [ ] test.count # When a function takes a closure as a parameter, when do you want to mark is as escaping? - [x] when it's executed after the function returns - [ ] when it's scope is undefined - [ ] when it's lazy loaded - [ ] all of these answers # What's wrong with this code? ```swift class Person { var name: String var address: String } ``` - [x] Person has no initializers. - [ ] Person has no base class. - [ ] var name is not formatted corrrectly. - [ ] address is a keyword. # What is the value of names after this code is executed? ```swift let names = ["Bear", "Joe", "Clark"] names.map { (s) -> String in return s.uppercased() } ``` - [ ] ["BEAR", "JOE", "CLARK"] - [ ] ["B", "J", "C"] - [x] ["Bear", "Joe", "Clark"] - [ ] This code contains an error. # What describes this line of code? ```swift let val = 5 ``` - [x] 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 # What is the error in this code? ```swift extension String { var firstLetter: Character = "c" { didSet { print("new value") } } } ``` - [x] Extensions can't add properties. // although extensions technically can't contain stored properties - [ ] Nothing is wrong with it. - [ ] didSet takes a parameter. - [ ] c is not a character. # didSet and willSet are examples of **\_**? - [x] property observers - [ ] key properties - [ ] all of these answers - [ ] newOld value calls # What is wrong with this code? ```swift self.callback = { self.attempts += 1 self.downloadFailed() } ``` - [x] Use of self inside the closure causes retain cycle. - [ ] You cannot assign a value to closure in this manner. - [ ] You need to define the type of closure explicitly. - [ ] There is nothing wrong with this code. # How many values does vals have after this code is executed? ```swift var vals = Set = ["4", "5", "6"] vals.insert("5") ``` - [ ] three - [ ] four - [ ] eight - [x] This code contains an error. # How can you avoid a strong reference cycle in a closure? - [x] Use a capture list to set class instances of weak or 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. # What is wrong with this code? ```swift if let s = String.init("some string") { print(s) } ``` - [x] This 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. # Which code snippet correctly creates a typealias closure? - [x] typealias CustomClosure: () -> () - [ ] typealias CustomClosure { () -> () } - [ ] typealias CustomClosure -> () -> () - [ ] typealias CustomClosure -> () {} # How do you reference class members from within a class? - [x] self - [ ] instance - [ ] class - [ ] this # All value types in Swift are **\_** under the hood? - [x] structs - [ ] classes - [ ] optionals - [ ] generics # What is the correct way to add a value to this array? ```swift var strings = [1, 2, 3] ``` - [x] all of these answers - [ ] strings.append(4) - [ ] strings.insert(5, at: 1) - [ ] strings += [5] # How many times will this loop be executed? ```swift for i in 0...100 { print(i) } ``` - [ ] 0 - [x] 101 - [ ] 99 - [ ] 100 # What can AnyObject represent? - [ ] an instance of any class - [ ] an instance of function type - [x] all of these answers - [ ] an instance of an optional type # What is the value of t after this code is executed? ```swift let names = ["Larry", "Sven", "Bear"] let t = names.enumerated().first().offset ``` - [x] This code is invalid. - [x] This code does not compile. - [ ] 0 - [ ] 1 - [ ] Larry # What is the value of test after this code executes? ```swift let vt = (name: "ABC", val: 5) let test = vt.0 ``` - [x] ABC - [ ] 0 - [ ] 5 - [ ] name # What is the base class in this code? ```swift class LSN : MMM { } ``` - [x] MMM - [ ] LSN - [ ] There is no base class. - [ ] This code is invalid. # What does this code print to the console? ```swift 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" ``` - [x] 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 # What must a convenience initializer call? - [ ] a base class convenience initializer - [ ] either a designated or another convenience initializer - [x] a designated initializer - [ ] none of these answers # Which object allows you access to specify that a block of code runs in a background thread? - [ ] DispatchQueue.visible - [x] DispatchQueue.global - [ ] errorExample need to be labeled as `throws`. - [ ] DispatchQueue.background # What is the inferred type of x? ```swift let x = ["a", "b", "c"] ``` - [ ] `String[]` - [x] `Array` - [ ] `Set` - [ ] `Array` # What is the value of `oThings` after this code is executed? ```swift let nThings: [Any] = [1, "2", "three"] let oThings = nThings.reduce("") { "\($0)\($1)" } ``` - [ ] 11212three - [ ] 115 - [x] 12three - [ ] Nothing, this code is invalid. # How would you call a function that throws errors and also returns a value? - [ ] `!try` - [x] `try?` - [ ] `try!` - [ ] `?try` # What is wrong with this code? ```swift protocol TUI { func add(x1 : Int, x2 : Int) -> Int { return x1 + x2 } } ``` - [ ] Protocol functions cannot have return types. - [x] Protocol functions cannot have implementations. - [ ] Nothing is wrong with it. - [ ] `add` is a reserved keyword. # In this code, what are `wheels` and `doors` examples of? ```swift class Car { var wheels: Int = 4 let doors = 4 } ``` - [ ] class members - [ ] This code is invalid. - [ ] class fields - [x] class properties # How do you designated a failable initializer? - [ ] You cannot - [ ] deinit - [x] `init?` - [ ] init # What is printed when this code is executed? ```swift let dbl = Double.init("5a") print(dbl ?? ".asString()") ``` - [ ] five - [ ] 5a - [x] `.asString()` - [ ] 5 # In the function below, what are `this` and `toThat` examples of? ```swift func add(this x: Int, toThat y: Int)->{} ``` - [ ] none of these answers - [ ] local terms - [x] argument labels - [ ] parameters names # What is wrong with this code? ```swift for (key, value) in [1: "one", 2: "two"]{ print(key, value) } ``` - [ ] The interaction source is invalid - [ ] The interaction variable is invalid - [x] There is nothing wrong with this code - [ ] The comma in the print is misplaced # Which of these choices is associated with unit testing? - [ ] XCTest - [x] all of these answers - [ ] @testable - [ ] XCAssert # In the code below, what is width an example of? ```swift class Square{ var height: Int = 0 var width : Int { return height } } ``` - [ ] This code contains error - [ ] a closure - [x] a computed property - [ ] lazy loading # What data type is this an example of? ```swift let vals = ("val", 1) ``` - [ ] a dictionary - [x] a tuple - [ ] an optional - [ ] This code contains error # What is wrong with this code? ```swift var x = 5 x = 10.0 ``` - [x] You cannot assign a Double to a variable of type Int - [ ] x is undefined - [ ] x is a constant - [ ] x has no type # What will this code print to the console? ```swift var items = ["a":1, "b":2, "c":"test"] as [String: Any] items["c"] = nil print(items["c"] as Any) ``` - [ ] Any - [ ] test - [ ] 1,2,3 - [x] nil # What is wrong with this code? ```swift let val = 5.0 + 10 ``` - [x] There is nothing wrong with this code - [ ] val is a constant and cannot be changed - [ ] 5.0 and 10 are different types - [ ] There is no semicolon # How many parameters does the initializer for Test have? ```swift struct Test{ var score: Int var date: Date } ``` - [ ] zero - [ ] This code contains an error - [x] two - [ ] Structs do not have initializers # What prints to the console when executing this code? ```swift let x = try? String.init("test") print(x) ``` - [ ] nil - [ ] Nothing - this code contains an error - [x] Optional("test") - [ ] test # How can you sort this array? ```swift var vals = [1,2,3] ``` - [ ] `vals.sort { $0 < $1 }` - [ ] `vals.sort { (s1, s2) in s1 < s2 }` - [ ] `vals.sort(by: <)` - [x] all of these answers # DispatchQueue.main.async takes a block that will be - [ ] not executed - [x] executed in the main queue - [ ] none of these answers - [ ] executed on the background thread # When is deinit called? - [ ] When a class instance needs memory - [x] All of these answers - [ ] When the executable code is finished - [ ] When a class instance is being removed from memory # How do you declare an optional String? - [x] String? - [ ] Optional[String] - [ ] [String]? - [ ] ?String # How many times this code will be executed? —OR— How many times will this loop be performed? ```swift for i in ["0", "1"]{ print(i) } ``` - [ ] one - [x] two - [ ] three - [ ] This code does not compile # What does this code print? ```swift let names = ["Bear", "Tony", "Svante"] print(names[1]+"Bear") ``` - [ ] 1Bear - [ ] BearBear - [x] TonyBear - [ ] Nothing, this code is invalid # What is true of this code? ```swift let name: String? ``` - [ ] name can hold only a string value. - [x] name can hold either a string or nil value. - [ ] Optional values cannot be `let` constants. - [ ] Only non-empty string variables can be stored in name. # What is the value of `val` after this code is executed? ```swift let i = 5 let val = i * 6.0 ``` - [x] This code is invalid. - [ ] 6 - [ ] 30 - [ ] 0 # What does this code print? ```swift enum Positions : Int { case first, second, third, other } print (Positions.other.rawValue) ``` - [x] 3 - [ ] 0 - [ ] other - [ ] nil # What is printed to the console when this code is executed? ```swift "t".forEach { (char) in print(char) } ``` - [ ] nil - [ ] Nothing, since the code contains an error - [x] t - [ ] zero # What prints when this code is executed? ```swift let s1 = ["1", "2", "3"] .filter { $0 > "0" } .sorted { $0 > $1 } print(s1) ``` - [ ] [] - [x] ["3", "2", "1"] - [ ] [321] - [ ] ["1", "2", "3"] # What enumeration feature allows them to store case-specific data? (Question does not make that much sense though. ) - [x] associated values - [ ] integral values - [ ] raw values - [ ] custom values # In the code below, AOM must be a(n)? ```swift class AmP : MMM, AOM { } ``` - [ ] class - [x] protocol - [ ] enumeration - [ ] struct # What is the value of numbers in the code below? ```swift let numbers = [1,2,3,4,5,6].filter{ $0 % 2 == 0} ``` - [ ] [1,3,5] - [ ] [] - [x] [2,4,6] - [ ] nil # What is the type of `vals` in this code? ```swift let vals = ["a", 1, "Hi"] ``` - [ ] Array(char) - [x] [Any] - [ ] Array - [ ] [Generic] # How can you extract val to `x` in tuple `vt` ```swift let vt = (name: "ABC", val: 5) ``` - [ ] let x = vt.1 - [x] all of these answers - [ ] let x = vt.val - [ ] let (`_`, x) = vt