[{"id":1,"question":"What is this code an example of?","code":"swift let val = (Double)6","reference":"```","choices":[{"text":"a syntax issue","answer":true,"code":false},{"text":"typecasting","answer":false,"code":false},{"text":"assignment","answer":false,"code":false},{"text":"initialization","answer":false,"code":false}]},{"id":2,"question":"What is the error in this code?","code":"swift let x = 5 guard x == 5 { return }","reference":"```","choices":[{"text":"The guard is missing the else.","answer":true,"code":false},{"text":"Nothing is wrong.","answer":false,"code":false},{"text":"The guard is missing a then.","answer":false,"code":false},{"text":"The comparison is wrong.","answer":false,"code":false}]},{"id":3,"question":"What is the raw/underlying type of this enum?","code":"swift enum Direction { case north, south, east, west }","reference":"```","choices":[{"text":"There is 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error","answer":true,"code":false},{"text":"1","answer":false,"code":false},{"text":"2","answer":false,"code":false},{"text":"nil","answer":false,"code":false}]},{"id":9,"question":"What is the value of test in this code?","code":"swift var test = 1 == 1","reference":"```","choices":[{"text":"TRUE","answer":true,"code":false},{"text":"YES","answer":false,"code":false},{"text":"1","answer":false,"code":false},{"text":"This code contains an error","answer":false,"code":false}]},{"id":10,"question":"What is the value of y?","code":"swift var x: Int? let y = x ?? 5","reference":"```","choices":[{"text":"5","answer":true,"code":false},{"text":"0","answer":false,"code":false},{"text":"nil","answer":false,"code":false},{"text":"This code contains an error","answer":false,"code":false}]},{"id":11,"question":"What is the type of this function?","code":"swift func add(a: Int, b: Int) -> Int { return a+b }","reference":"```","choices":[{"text":"Int","answer":false,"code":false},{"text":"(Int, 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classes","answer":false,"code":false}]},{"id":14,"question":"What is the type of value1 in this code?","code":"swift let value1 = \"(\"test\".count)\"","reference":"```","choices":[{"text":"String","answer":true,"code":false},{"text":"Int","answer":false,"code":false},{"text":"null","answer":false,"code":false},{"text":"test.count","answer":false,"code":false}]},{"id":15,"question":"When a function takes a closure as a parameter, when do you want to mark is as escaping?","code":"","reference":"","choices":[{"text":"when it's executed after the function returns","answer":true,"code":false},{"text":"when it's scope is undefined","answer":false,"code":false},{"text":"when it's lazy loaded","answer":false,"code":false},{"text":"all of these answers","answer":false,"code":false}]},{"id":16,"question":"What's wrong with this code?","code":"swift class Person { var name: String var address: String }","reference":"```","choices":[{"text":"Person has no initializers.","answer":true,"code":false},{"text":"Person has no base class.","answer":false,"code":false},{"text":"var name is not formatted corrrectly.","answer":false,"code":false},{"text":"address is a keyword.","answer":false,"code":false}]},{"id":17,"question":"What is the value of names after this code is executed?","code":"swift let names = [\"Bear\", \"Joe\", \"Clark\"] names.map { (s) -> String in return s.uppercased() }","reference":"```","choices":[{"text":"[\"BEAR\", \"JOE\", \"CLARK\"]","answer":false,"code":false},{"text":"[\"B\", \"J\", \"C\"]","answer":false,"code":false},{"text":"[\"Bear\", \"Joe\", \"Clark\"]","answer":true,"code":false},{"text":"This code contains an error.","answer":false,"code":false}]},{"id":18,"question":"What describes this line of code?","code":"swift let val = 5","reference":"```","choices":[{"text":"a constant named val of type Int","answer":true,"code":false},{"text":"a variable named val of type item","answer":false,"code":false},{"text":"a constant named val of type Number","answer":false,"code":false},{"text":"a variable named val of type Int","answer":false,"code":false}]},{"id":19,"question":"What is the error in this code?","code":"swift extension String { var firstLetter: Character = \"c\" { didSet { print(\"new value\") } } }","reference":"```","choices":[{"text":"Extensions can't add properties. // although extensions technically can't contain stored properties","answer":true,"code":false},{"text":"Nothing is wrong with it.","answer":false,"code":false},{"text":"didSet takes a parameter.","answer":false,"code":false},{"text":"c is not a character.","answer":false,"code":false}]},{"id":20,"question":"didSet and willSet are examples of **_**?","code":"","reference":"","choices":[{"text":"property observers","answer":true,"code":false},{"text":"key properties","answer":false,"code":false},{"text":"all of these answers","answer":false,"code":false},{"text":"newOld value calls","answer":false,"code":false}]},{"id":21,"question":"What is wrong with this code?","code":"swift self.callback = { self.attempts += 1 self.downloadFailed() }","reference":"```","choices":[{"text":"Use of self inside the closure causes retain cycle.","answer":true,"code":false},{"text":"You cannot assign a value to closure in this manner.","answer":false,"code":false},{"text":"You need to define the type of closure explicitly.","answer":false,"code":false},{"text":"There is nothing wrong with this code.","answer":false,"code":false}]},{"id":22,"question":"How many values does vals have after this code is executed?","code":"swift var vals = Set = [\"4\", \"5\", \"6\"] vals.insert(\"5\")","reference":"```","choices":[{"text":"three","answer":false,"code":false},{"text":"four","answer":false,"code":false},{"text":"eight","answer":false,"code":false},{"text":"This code contains an error.","answer":true,"code":false}]},{"id":23,"question":"How can you avoid a strong reference cycle in a closure?","code":"","reference":"","choices":[{"text":"Use a capture list to set class instances of weak or unowned.","answer":true,"code":false},{"text":"You can't, there will always be a danger of strong reference cycles inside a closure.","answer":false,"code":false},{"text":"Initialize the closure as read-only.","answer":false,"code":false},{"text":"Declare the closure variable as lazy.","answer":false,"code":false}]},{"id":24,"question":"What is wrong with this code?","code":"swift if let s = String.init(\"some string\") { print(s) }","reference":"```","choices":[{"text":"This String initializer does not return an optional.","answer":true,"code":false},{"text":"String does not have an initializer that can take a String.","answer":false,"code":false},{"text":"= is not a comparison.","answer":false,"code":false},{"text":"Nothing is wrong with this code.","answer":false,"code":false}]},{"id":25,"question":"Which code snippet correctly creates a typealias closure?","code":"","reference":"","choices":[{"text":"typealias CustomClosure: () -> ()","answer":true,"code":false},{"text":"typealias CustomClosure { () -> () }","answer":false,"code":false},{"text":"typealias CustomClosure -> () -> ()","answer":false,"code":false},{"text":"typealias CustomClosure -> () {}","answer":false,"code":false}]},{"id":26,"question":"How do you reference class members from within a class?","code":"","reference":"","choices":[{"text":"self","answer":true,"code":false},{"text":"instance","answer":false,"code":false},{"text":"class","answer":false,"code":false},{"text":"this","answer":false,"code":false}]},{"id":27,"question":"All value types in Swift are **_** under the hood?","code":"","reference":"","choices":[{"text":"structs","answer":true,"code":false},{"text":"classes","answer":false,"code":false},{"text":"optionals","answer":false,"code":false},{"text":"generics","answer":false,"code":false}]},{"id":28,"question":"What is the correct way to add a value to this array?","code":"swift var strings = [1, 2, 3]","reference":"```","choices":[{"text":"all of these answers","answer":true,"code":false},{"text":"strings.append(4)","answer":false,"code":false},{"text":"strings.insert(5, at: 1)","answer":false,"code":false},{"text":"strings += [5]","answer":false,"code":false}]},{"id":29,"question":"How many times will this loop be executed?","code":"swift for i in 0...100 { print(i) }","reference":"```","choices":[{"text":"0","answer":false,"code":false},{"text":"101","answer":true,"code":false},{"text":"99","answer":false,"code":false},{"text":"100","answer":false,"code":false}]},{"id":30,"question":"What can AnyObject represent?","code":"","reference":"","choices":[{"text":"an instance of any class","answer":false,"code":false},{"text":"an instance of function type","answer":false,"code":false},{"text":"all of these answers","answer":true,"code":false},{"text":"an instance of an optional 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0/68

What is this code an example of?