все советую про солид читать дядюшку боба, а не очередного блохера который решил поразить всех умом и сообразительностью:
The SOLID principles are not rules. They are not laws. They are not perfect truths. The are statements on the order of “An apple a day keeps the doctor away.” This is a good principle, it is good advice, but it’s not a pure truth, nor is it a rule.
The principles are mental cubby-holes. They give a name to a concept so that you can talk and reason about that concept. They provide a place to hang the feelings we have about good and bad code. They attempt to categorize those feelings into concrete advice. In that sense, the principles are a kind of anodyne. Given some code or design that you feel bad about, you may be able to find a principle that explains that bad feeling and advises you about how to feel better.
https://sites.google.com/site/unclebobconsultingllc/getting-a-solid-startКак бы дядя боб. Это просто советы по архитектуре, можешь применить и получить лучший результат в фп применяй, а если нет, то не применяй. Все просто. И для ООП работает так же.