getByPath function

dynamic getByPath(Json json, SimpleJsonPath path)

tries to follow a given path in a json mapping

e.g.

var json = {'test': [2, {'hallo': 'welt'}]};
var path = ['test', 1, 'hallo'];
var result = getByPath(json, path);
# result == 'welt';

if [path] is empty, the [json] is returned as is
will raise a [JsonPathNotFoundException] if the path is not found

Implementation

dynamic getByPath(Json json, SimpleJsonPath path) {
  if (path.isEmpty) {
    return json;
  }
  SimpleJsonPath currentPath = [];
  dynamic current = json;

  // iterate over each part segment
  for (var part in path) {
    currentPath.add(part);
    if (part.runtimeType == int) {
      if (current.runtimeType != List) {
        throw JsonPathException(
            'Element `${currentPath.prettyPrint()}` is not a list, '
                'but a `${current.runtimeType}`.', code: 234839405);
      }
      current = current[part];
    } else if (part.runtimeType == String) {

      // check if the thing is map-able
      // note that jsonDecode returns a _InternalLinkedHashMap
      // which for whatever reason is not a Map, so we cannot just check it
      if (current.containsKey(part)) {
        current = current[part];
      } else {
        throw JsonPathException(
            'Element `${currentPath.prettyPrint()}` was not found', code: 429348534);
      }
    } else { // invalid path segment
      throw JsonPathException('Path at ${currentPath.prettyPrint()} '
          'is not a valid path. '
          'Only String and Integer elements are allowed.', code: 4583904);
    }
  }

  return current;
}