Data from notification.userInfo

Question

I am reading an usb-rawHID-device with

var read_byteArray = [UInt8](repeating: 0x00, count: BUFFER_SIZE)
var result = rawhid_recv(0, &read_byteArray, Int32(BUFFER_SIZE), 50)

I can read the read_byteArray with

for  i in 0...16
        {
           print(" \(read_byteArray[i])", terminator: "")
        }

+++ new read_byteArray in Timer: 0 9 69 0 0,...

I then want to distribute the data with a notification.

        let nc = NotificationCenter.default
        nc.post(name:Notification.Name(rawValue:"newdata"),
                object: nil,
                userInfo: ["data":read_byteArray])

I register the notification and read it with

@objc func newDataAktion(_ notification:Notification) 
{
  print("new Data")
  let data = notification.userInfo?["data"]
  print("data: \(String(describing: data)) \n") // data: Optional([0, 9, 51, 0,....
  if let d = notification.userInfo!["data"] 
  {
     print("d: \(d)\n") // d: [0, 9, 56, 0, 0,... 
     let t = type(of:d)
     print("typ: \(t)\n") // typ: Array<UInt8>
  }   
}

The data is of type Array, but my attempts to read an element of this array with

print("element: \(d[1])\n")

gives me the error

Type 'Any' has no subscript members

How can I get the UInt8 elements out of the data?

Answer 1

The user info dictionary is of type [String: Any] so when you grab the key out of if you should also cast it to the correct type (otherwise its wrapped in Any and its not an array; type(of:) can tell you its an [UInt8] at run time but the compiler can't know that at compile time unless you tell it):

  if let d = notification.userInfo?["data"] as? [UInt8] {
     d.forEach{ print($0) }
  }