One Of Schema

Offers a choice between a number of child schemas.

Use a oneOf schema to represent either the selection of one of many constant values (e.g. a select box or dropdown) or alternative sections of a form (e.g. when the user can complete either a form in tab A or tab B).

Sometimes you may want to load a step with an option selected - for example in order to retain the selected option after a refresh.

To figure out which item to select, we look at the step model. Clients will first populate the form with the model, and then inspect each oneOf option and compare them with the model to see which ones match. If no options match, or if multiple match, we will not select anything.

This is the full matching algorithm:

function isPartialMatch(optionValue, stepModel) {
  if (isArray(optionValue) && isArray(stepModel)) {
    return (
      optionValue.length === stepModel.length &&
      optionValue.every((value, index) => isPartialModelMatch(value, stepModel[index]))
    );
  }
  if (isObject(optionValue) && isObject(stepModel)) {
    // Don't look at properties with null values
    const nonNullishKeysInBoth = intersection(nonNullishKeys(optionValue), nonNullishKeys(stepModel));
    return (
      nonNullishKeysInBoth.length > 0 &&
      nonNullishKeysInBoth.every((key) => isPartialModelMatch(optionValue[key], stepModel[key]))
    );
  }
  return optionValue === stepModel;
};

Persisted fields are ignored, as are keys with nullish values.

If your oneOf options share schema property names, you will need to add a discriminator to ensure successful preselection. For example - if the following example did not contain a const type discriminator and the step model was { "name": "Jane" }, we would not know which option to select, as both match. Conversely, if you remove the name property from the schemas, the const discriminator would be unnecessary, as there would be no ambiguity. *

schemas {
    obj {
        title = "Iban option"
        properties {
            const("type") {
                value = JsonPrimitive("IBAN")
            }
            string("iban") {
                title = "IBAN"
            }
            string("name") {
                title = "Name"
            }
        }
    }
    obj {
        title = "Bic option"
        properties {
            const("type") {
                value = JsonPrimitive("BIC")
            }
            string("bic") {
                title = "BIC"
            }
            string("name") {
                title = "Name"
            }
        }
    }
}