writeClassDecode method

Implementation

@override
void writeClassDecode(
  CppOptions generatorOptions,
  Root root,
  Indent indent,
  Class classDefinition, {
  required String dartPackageName,
}) {
  // Returns the expression to convert the given EncodableValue to a field
  // value.
  String getValueExpression(NamedType field, String encodable) {
    if (field.type.isEnum) {
      return '(${field.type.baseName})(std::get<int32_t>($encodable))';
    } else if (field.type.baseName == 'int') {
      return '$encodable.LongValue()';
    } else if (field.type.baseName == 'Object') {
      return encodable;
    } else {
      final HostDatatype hostDatatype =
          getFieldHostDatatype(field, _shortBaseCppTypeForBuiltinDartType);
      if (field.type.isClass) {
        return _classReferenceFromEncodableValue(hostDatatype, encodable);
      } else {
        return 'std::get<${hostDatatype.datatype}>($encodable)';
      }
    }
  }

  _writeFunctionDefinition(indent, 'FromEncodableList',
      scope: classDefinition.name,
      returnType: classDefinition.name,
      parameters: <String>['const EncodableList& list'], body: () {
    const String instanceVariable = 'decoded';
    final Iterable<_IndexedField> indexedFields = indexMap(
        getFieldsInSerializationOrder(classDefinition),
        (int index, NamedType field) => _IndexedField(index, field));
    final Iterable<_IndexedField> nullableFields = indexedFields
        .where((_IndexedField field) => field.field.type.isNullable);
    final Iterable<_IndexedField> nonNullableFields = indexedFields
        .where((_IndexedField field) => !field.field.type.isNullable);

    // Non-nullable fields must be set via the constructor.
    String constructorArgs = nonNullableFields
        .map((_IndexedField param) =>
            getValueExpression(param.field, 'list[${param.index}]'))
        .join(',\n\t');
    if (constructorArgs.isNotEmpty) {
      constructorArgs = '(\n\t$constructorArgs)';
    }
    indent
        .format('${classDefinition.name} $instanceVariable$constructorArgs;');

    // Add the nullable fields via setters, since converting the encodable
    // values to the pointer types that the convenience constructor uses for
    // nullable fields is non-trivial.
    for (final _IndexedField entry in nullableFields) {
      final NamedType field = entry.field;
      final String setterName = _makeSetterName(field);
      final String encodableFieldName =
          '${_encodablePrefix}_${_makeVariableName(field)}';
      indent.writeln('auto& $encodableFieldName = list[${entry.index}];');

      final String valueExpression =
          getValueExpression(field, encodableFieldName);
      indent.writeScoped('if (!$encodableFieldName.IsNull()) {', '}', () {
        indent.writeln('$instanceVariable.$setterName($valueExpression);');
      });
    }

    // This returns by value, relying on copy elision, since it makes the
    // usage more convenient during deserialization than it would be with
    // explicit transfer via unique_ptr.
    indent.writeln('return $instanceVariable;');
  });
}