How in swift to convert Int16 to two UInt8 Bytes

Question

I have some binary data that encodes a two byte value as a signed integer.

bytes[1] = 255  // 0xFF
bytes[2] = 251  // 0xF1

Decoding

Answer 1

extension Int16 {
    var twoBytes : [UInt8] {
        let unsignedSelf = UInt16(bitPattern: self)
        return [UInt8(truncatingIfNeeded: unsignedSelf >> 8),
                UInt8(truncatingIfNeeded: unsignedSelf)]
    }
}

var test : Int16 = -15
test.twoBytes // [255, 241]