getRequiredProp<V> method

V getRequiredProp<V>(V accessProp(T spiedView), { required V orElse(), })

Returns the value of the prop read within accessProp if it's specified, or the result of orElse otherwise.

Useful for safely accessing required props in a "partial" props map that may not contain them.

See also: getRequiredPropOrNull.

For example:

class FooProps on UiProps {
  late String requiredProp;
}

void example(FooProps props) {
  // Unsafe: this will throw if requiredProp is not specified
  final requiredProp = props.requiredProp;

  final requiredPropOrDefault =
      props.getRequiredProp((p) => p.requiredProp, () => 'default value');
}

Implementation

V getRequiredProp<V>(V Function(T spiedView) accessProp, {required V Function() orElse}) {
  if (!containsProp(accessProp)) return orElse();

  // Provide a more helpful error when a non-nullable prop is specified with `null` somehow.
  assert(() {
    try {
      accessProp(this);
    } on TypeError catch (e, st) {
      final key = getPropKey(accessProp);
      final value = this[key];
      if (value == null) {
        throw AssertionError('Error reading typed prop, likely due to props map containing explicit `null` value:'
            ' `"$key": null`.\nOriginal error: $e\n$st');
      }
      rethrow;
    }
    return true;
  }());

  return accessProp(this);
}