Casting empty strings to null

[EvHaus]

With a schema like this:

const schema = Type.Object({
	myField: Type.Union([t.Null(), t.String()]),
);

I'm looking for some way to get Typebox to cast empty strings to null. I want this behavior:

const converted = Value.Convert(schema, {myField: 'howdy'});
// -> I want {myField: 'howdy'}. This works today.

const converted = Value.Convert(schema, {myField: ''});
// -> I want {myField: null}. This doesn't work.

Neither Convert nor Cast will do that at the moment, so I'm assuming I need to add some custom code to handle this. Is the Visit method exposed in a way that I could use it to iterate through the schema myself, detect the union that supports Null values and ensure empty strings change to nulls?

[EvHaus]

I think I found my answer -- Type.Transform. I changed my schema to:

const schema = Type.Object({
  myField: Type.Transform(
    Type.Union([t.Null(), t.String()])
  )
  .Decode((value) => {
    if (value === '') return null;
    return value;
  })
  .Encode((value) => {
    if (value === null) return '';
    return value;
  })
);

And now it works.