decodeUnion method

Object decodeUnion(String jsonPath, Object? jsonData, String field, Map<String, JsonDecoderCallback<Object>> decoders,)

Decode a JSON object that is expected to be one of several choices, where the choices are disambiguated by the contents of the field field. decoders is a map from each possible string in the field to the decoder that should be used to decode the JSON object.

Implementation

Object decodeUnion(String jsonPath, Object? jsonData, String field,
    Map<String, JsonDecoderCallback> decoders) {
  if (jsonData is Map) {
    if (!jsonData.containsKey(field)) {
      throw missingKey(jsonPath, field);
    }
    var disambiguatorPath = '$jsonPath[${json.encode(field)}]';
    var disambiguator = decodeString(disambiguatorPath, jsonData[field]);
    var decoder = decoders[disambiguator];
    if (decoder == null) {
      throw mismatch(
          disambiguatorPath, 'One of: ${decoders.keys.toList()}', jsonData);
    }
    return decoder(jsonPath, jsonData);
  } else {
    throw mismatch(jsonPath, 'Map', jsonData);
  }
}