What is an opaque type in Swift?

What tool does Apple provide for developers to graphically design the user interface (UI) of an app?

To which of the following inherited properties can property observers not be added?

What do unsafe unowned references in Swift provide?

What is the correct way to declare class-only protocols in Swift?

Which one of the following is not allowed for methods of value types in Swift by default?

Are the following lines of code correct in Swift?

struct MixedRectangle {

@SmallNumber var height: Int = 1

@SmallNumber(maximum: 9) var width: Int = 2

}

What will be the output of the following lines of code?

struct SomeStruct {

static let mult = 8

static subscript(i: Int, j: Int) -> Int {

return mult * i * j

}

}

print(SomeStruct[8, 8])

What will be the output of the following code?

var airports: [String: String] = ["YYZ": "Toronto Pearson", "DUB": "Dublin"]

var string = String()

for airportCode in airports.values {

 string.append(airportCode)

}

print(string)