How the Unity Update(), OnEnable(), etc. methods are called?

[beatdesign]

Is there someone that is able to explain in simple words how these functions are called?
I guess is somthing like this:

• Unity collects all Monobehaviour class and sort them depending of the execution order in a list.
• Then at each frame Unity calls Update() function on them. But Update() method is not public, and it isn’t an override function, so…

how exactly is this performed? Does Unity use some sort of Reflection system?
Thank you!

[kdgalla]

@beatdesign

how exactly is this performed? Does Unity use some sort of Reflection system?

Yes. I can’t really find a good source to confirm that, but here is this:
https://stackoverflow.com/questions/32537997/why-are-the-monobehaviour-methods-not-implemented-for-overriding

[LiterallyJeff]

Here’s another good answer about it, confirming that it is not System.Reflection being used (as I imagine that would be very slow):

How does Unity execute its methods?

No, Unity doesn’t use System.Reflection to find a magic method every time it needs to call one.

Instead, the first time a MonoBehaviour of a given type is accessed the underlying script is inspected through scripting runtime (either Mono or IL2CPP) whether it has any magic methods defined and this information is cached. If a MonoBehaviour has a specific method it is added to a proper list, for example if a script has Update method defined it is added to a list of scripts which need to be updated every frame.

During the game Unity just iterates through these lists and executes methods from it — that simple. Also, this is why it doesn’t matter if your Update method is public or private.