views – How can I get the field definition values ​​in a hook_views_query_alter?

This is somewhat related to my previous question, I use a hook_views_query_alter to only show the results of the last (last) value in a list field, then in this set only, show the results with the last (last) value in another list field. So with a bunch of articles, I want to show those of the last issue in the last volume. I think I will need these field values ​​to use in my alter query, but I have trouble getting them, for example in $ view-> field["field_article_volume"]. I'm wondering now if I'm okay on this issue, it seems to be a common scenario, so I would not want to complicate it further than necessary. Is there a way to take these field values ​​and use them as arguments in my helper functions to subsequently change the value of the condition?