I think I was confused actually - I thought that the QOMFactory could be encapsulated within the ``ExpressionVisitor``, but this class is instantiated within the ``QueryBuilder`` anyway so we still need to pass it in. And the Factory is still used directly for ``orderBy``.

Maybe Im being lazy, but I think I prefer to just carry on passing it as an argument, as its easier to mock and the QOMFactory is at the end of a pretty big method chain ($this->session->workspace->queryManage->qomFactory). But maybe I should change it.