Dynamic Enum

The dynamic enum field allows for the enum options of a field to be populated dynamically from the data in another form.

Usage

Imagine you have an array of centres that you would like people to enter in in the form, in the centres key. However, you have another spot in the form, the location field, which you would like to show a select box with dynamically populated options based on the centres you chose. In the schema:

{
  "centres": {
      "type": "array",
      "items": {
          "type": "object",
          "properties": {
              "name": {"type": "string"},
              "location": {"type": "string"}
          }
      }
  },
  "location": {"type": "string"}
}

in the ui schema:

{
    "location": {
        "ui:field": "cff:dynamicEnum",
        "ui:options": {
          "cff:dynamicEnumDataAccessor": "centres.name"
        }
    }
}

We see that cff:dynamicEnumDataAccessor is used to access the data from which the options are populated. Currently, this accessor allows the same notation as in lodash's get function; it also supports, to a limited level, getting properties of objects in arrays one level deep.