std::unique_ptr<QJsonObject> Archiver::serialise(const Component* component)
 {
    JSONVisitor visitor;
    component->visit(&visitor);

    return visitor.jsonData();
 }

'return': cannot convert from 'const QJsonObject' to
  'std::unique_ptr<QJsonObject,std::default_delete<_Ty>>

return std::make_unique<QJsonObject>(visitor.jsonData())