execute method

@override List execute(List results, Map<String, dynamic> passed)

The iterable, nested function that evaluates the entire FHIRPath expression one object at a time

Implementation

@override
List execute(List results, Map<String, dynamic> passed) {
  // The regular .execute method on CommaParser does not implement the
  // short-circuit logic. Bespoke execution path required.
  if (value.first is! CommaParser) {
    // While this happens at eval time, it is due to incorrect syntax
    throw FhirPathInvalidExpressionException(
      'The function iif must have a criterion expression, followed by '
      ' a true-result collection, and an optional other-wise-result. '
      'Instead it has: ${value.first}',
    );
  }

  final CommaParser criterionResultParser = value.first as CommaParser;

  FhirPathParser criterionExpressionParser;
  FhirPathParser trueResultParser;
  FhirPathParser? otherwiseResultParser;

  if (criterionResultParser.before.first is CommaParser) {
    criterionExpressionParser =
        (criterionResultParser.before.first as CommaParser).before;
    trueResultParser =
        (criterionResultParser.before.first as CommaParser).after;
    otherwiseResultParser = criterionResultParser.after;
  } else {
    criterionExpressionParser = criterionResultParser.before;
    trueResultParser = criterionResultParser.after;
  }

  final criterionCollection =
      criterionExpressionParser.execute(results.toList(), passed);

  final criterion = SingletonEvaluation.toBool(criterionCollection,
      name: 'criterion expression', operation: 'iif', collection: results);

  // Short-circuit: Only evaluate what matches the criterion.
  if (criterion == true) {
    final newResults = trueResultParser.execute(results, passed);
    return newResults;
  } else {
    if (otherwiseResultParser == null) {
      return [];
    } else {
      return otherwiseResultParser.execute(results, passed);
    }
  }
}