Swift UUID -> Data code extension

UUID+DataExtension.swift

extension UUID {
   /// Errors thrown
   public enum LoadError: Error {
      case invalidUUIDData
   }

   /// Returns the raw bytes of the UUID as a Data object.
   ///
   /// Note that this method assumes a specific memory layout (the layout on the device calling the method)
   /// and as such may not be portable to other systems.
   public var uuidData: Data {
      var tempUUID = self.uuid
      return withUnsafePointer(to: &tempUUID) { rawUuidPtr in
         let bytes = UnsafeRawPointer(rawUuidPtr).assumingMemoryBound(to: UInt8.self)
         let capacity = MemoryLayout<uuid_t>.size
         return Data(bytes: bytes, count: capacity)
      }
   }

   /// Create a UUID object initialized with the bytes stored in the Data object
   ///
   /// - Parameter uuidData: The data object containing the binary form of the uuid
   /// - Returns: a UUID object initialized with the bytes stored in the Data object
   /// - Throws: Throws LoadError.invalidUUIDData if there aren't enough bytes, or if a UUID could not be created
   ///
   /// Note that this method assumes a specific memory layout (the layout on the device calling the method)
   /// and as such may not be portable to other systems.
   init(uuidData data: Data) throws {
      guard data.count >= MemoryLayout<uuid_t>.size else {
         throw LoadError.invalidUUIDData
      }

      let uuid: NSUUID = try data.withUnsafeBytes { rawBuffer in
         guard let bytes = rawBuffer.baseAddress?.assumingMemoryBound(to: UInt8.self) else {
            throw LoadError.invalidUUIDData
         }
         return NSUUID(uuidBytes: bytes)
      }

      self = uuid as UUID
   }
}

func testUUIDToFromData() {
   let uuid = UUID()
   let UIDS = uuid.uuidString
   let bytes = uuid.uuidData

   if let uuid2 = try? UUID(uuidData: bytes) {
      let UIDS2 = uuid2.uuidString
      XCTAssertEqual(UIDS, UIDS2)
   }
   else {
      XCTAssert(false, "Unable to load UUID from bytes")
   }
}

If transferring uuids between different systems, it might be better to use the string form of the uuid for storage and/or transmission

Thanks for sharing, however I got a warning when I used your code snippet.

The code snippet:

      var nsUUID: NSUUID?
      data.withUnsafeBytes { rawBytes in
         nsUUID = NSUUID(uuidBytes: rawBytes)
      }

The warning:

'withUnsafeBytes' is deprecated: use withUnsafeBytes<R>(_: (UnsafeRawBufferPointer) throws -> R) rethrows -> R instead

After some tries, I found the modification below would work.

      var nsUUID: NSUUID?
      data.withUnsafeBytes { rawBytes in
         nsUUID = NSUUID(uuidBytes: rawBytes.baseAddress!.assumingMemoryBound(to: UInt8.self))
      }

Hope this comment will help others.

Thanks @lbwanghr, I've updated the sample with your changes and cleaned the interface a bit