Swift optional pattern matching in a for-in loop

for_case_let.swift

// Source: https://docs.swift.org/swift-book/ReferenceManual/Patterns.html#grammar_optional-pattern

let arrayOfOptionalInts: [Int?] = [nil, 2, 3, nil, 5]

for case let number? in arrayOfOptionalInts {
    print("Found a \(number)")
}