Here I am at checkpoint 9 and I came up with two ways to solve it. The actual func way:

func mindBlown(_ input: [Int]?) -> Int { return input?.randomElement() ?? Int.random(in: 1...100) }
print(mindBlown(nil))       // This prints a random number.
print(mindBlown([0, 1]))    // This prints 0 or 1.

The neat way, although this one does require making the array first:

let array: [Int]? = nil
let mindBlown = array?.randomElement() ?? Int.random(in: 1...100)
print(mindBlown) // Depending on whether the array is nil or not,
                 // prints a random number from the array or anything from 1 to 100.

Did I miss anything obvious? Does the neat way qualify as a solution?

+1 for function name.

Look at all the concepts you've included! Optional variables. Nil coalescing operators. Type functions. Dual parameters. Array processing. Parameter name hiding.

All in one line of code.

Mind blown!

Thanks. :D That's how I felt when it worked. A lot of trial and error was involved and these concepts are certainly something that takes practice.

And thank you for replying to my questions so far. You have been very helpful an supportive and I truly appreciate it.