How can I avoid circular dependencies in my RPG game project?

I like the idea of a BuffHandler class which doesn't directly tie units and buffs together. It can act as a mediator that takes care of applying buffs and modifying unit stats. This way, both units and buffs can exist independently, reducing complexity.

You might want to create a separate class, like a BuffManager, to handle all things related to buffs. This class would manage any buffs applied to units, keeping track of their states and ensuring they get applied at the right times without letting the unit class directly handle them. This way, the unit remains focused only on its own state. I believe this will clean up your code considerably!

One way to handle this is to structure your buffs to be more like modifications or effects rather than having them directly tied to the unit. Consider having a 'Stats' class that both units and buffs interact with. Buffs can modify stats directly without knowing about the units themselves, which makes it easier to manage things.

A different solution could be to think in terms of components and maybe apply an ECS (Entity Component System) pattern. Here, you treat characters as entities and both units and buffs as components. This way, your character can own both without direct dependencies between units and buffs, leading to a more modular approach.

One approach you could try is to invert the dependency by using events or signals. It makes sense for units to have a list of buffs, but do buffs really need to know about the units they're applied to, except when executing? You might consider your buffs as parts of a "modification" list that implements an interface where they just accept a unit parameter for execution without tightly coupling the two classes. This can help reduce direct dependencies between them.