How to convert a double into a byte array in swift?

Question

I know how to do it in java (see here), but I couldn\'t find a swift equivalent for java\'s ByteBuffer, and consequently its .putDouble(double value) method.

Basically,

Answer 1

The accepted answers are dangerous because of the fact that the MemoryLayout provides you the size of the static type T!

To workaround the problem you should create a custom protocol and ask for Self in it:

protocol ByteConvertible {}

extension ByteConvertible {

    func toBytes() -> [UInt8] {

        let capacity = MemoryLayout.size
        var mutableValue = self
        return withUnsafePointer(to: &mutableValue) {

            return $0.withMemoryRebound(to: UInt8.self, capacity: capacity) {

                return Array(UnsafeBufferPointer(start: $0, count: capacity))
            }
        }
    }
}

I mentioned before that the accepted answers are dangerous and here is an example why:

let num = UInt8(42)
MemoryLayout.size(ofValue: num) //=> 1 byte as expected
let any: Any = num
MemoryLayout.size(ofValue: any) //=> 32 bytes which is what will happen in the generic functions from the all the answers 

Swift 3.0