Best way to deserialize optional elements...

[woolie]

I have an array an array of elements and each of the nodes have potentially optional elements. This kind of makes a mess of the simple deserialization. I wonder if anyone has advice for a cleaner way of doing this. For example:

<Note id="0">
  <Tie origin="true" destination="false" />
  <InstrumentArticulation>0</InstrumentArticulation>
  <Properties>
    <Property name="ConcertPitch">
      <Pitch>
          <Step>E</Step>
          <Accidental></Accidental>
          <Octave>3</Octave>
        </Pitch>
      </Property>
    </Properties>
  </Note>
  <Note id="1">
      <Accent>1</Accent>
      <InstrumentArticulation>0</InstrumentArticulation>
      <Properties>
        <Property name="ConcertPitch">
          <Pitch>
            <Step>E</Step>
            <Accidental></Accidental>
            <Octave>4</Octave>
          </Pitch>
        </Property>
      </Properties>
  </Note>
</Notes>

And the struct I'm deserializing into (eliding the sub types):

struct Note: XMLIndexerDeserializable {
	var id: Int
	var tie: Tie?
	var instrumentArticulation: Int
	var properties: [NoteProperty]

	static func deserialize(_ node: XMLIndexer) throws -> Self {
		let tieIndexer = node["Tie"]
		let tieElement = tieIndexer.element

		return try Note(
			id: node.value(ofAttribute: "id"),
			tie: tieElement != nil ? tieIndexer.value() : nil,
			instrumentArticulation: node["InstrumentArticulation"].value(),
			properties: node["Properties"]["Property"].value()
		)
	}
}

So as you can see, I am checking to see if the tie element is there (the one that only appears in note id=0 but not id=1) and if it is there I am getting the value(). Now, the first problem is that node["Tie"] throws for all of the Notes that don't have the Tie element.

Is this a problem? I sure would like a way to index that returns an optional instead of throwing (or returning an xmlError case).

All suggestions are welcome. This works fine, but seems inelegant and like I haven't RTFM'ed enough.

TIA

[drmohundro]

Any reason you're not using the tie: node["Tie"].value() there like below? The deserializer can handle optionals like this (if the left side is optional anyway):

struct Note: XMLIndexerDeserializable {
	var id: Int
	var tie: Tie?
	var instrumentArticulation: Int
	var properties: [NoteProperty]

	static func deserialize(_ node: XMLIndexer) throws -> Self {
		return try Note(
			id: node.value(ofAttribute: "id"),
			tie: node["Tie"].value(),
			instrumentArticulation: node["InstrumentArticulation"].value(),
			properties: node["Properties"]["Property"].value()
		)
	}
}

Disclaimer: I haven't tried running this code, so it might have some issues...

[woolie]

Not sure what I was doing wrong, but this works fine. TY For the sanity check.