Question

what I mean by that is:
I basically have a class that has too many properties and functions now. To remain performant and understandable, it needs to shrink somehow. But I still need all those properties and methods somewhere.
It’s like this right now:

class Apple

  float seedCount;
  ...
  ...about 25 variables and properties here.
  void Update() <-- a huge method that checks for each property and updates if so

In most cases the class needs almost none of those properties. In some cases in needs to be able to grow very selectively and gain a feature or lose a feature.
The only solution I have come up with, is that I create a bunch of classes and place some properties in there. I only initialize this classes object when one of those properties is needed, otherwise it remains null.

class Apple

  Seed seed;

Many problems because of that:
I constantly have to check for every single object and feature each frame. If the seed is not initialized I don’t have to calculate anything for it. If it is, I have to.
If I decided to put more than 1 property/feature into the Seed class, I need to check every single one of those aswell.
It just gets more and more complicated. The problem I have is therefore, that I need granular control over all the features and can’t split them intelligently into larger subclasses. Any form of subclass would just contain a bunch of properties that need to be checked and updated if wanted.
I can’t exactly create subclasses of Apple, because of the need for such high granular control. It would be madness to create as many classes as there are combinations of properties.
My main goal: I want short code.

Answer 1

It would be madness to create as many classes as there are combinations of properties.

Sounds like you might be looking for the Decorator Pattern. It’s purpose is to make it easier to manage objects that can have many different combinations of properties without an exponentially growing heirarchy. You just have one small subclass for each property or behavior (not necessarily one C# property, just something you can group together) and then you can compose them together at runtime.

In your case, each Apple decorator class will override your Update method, and make the calculations necessary for its parts, and then call base.Update to pass it to the next in line.

Your final answer will heavily depend on exactly what your “Apple” really is.