ARTICLE AD BOX
How are you doing?
I reviewed your question carefully and here are my opinions based on my experience.**
I think, Unity does not provide a built-in MonoBehaviour callback that runs when another component is added to the same GameObject.**
There is no OnComponentAdded() method in Unity.
MonoBehaviour only has lifecycle callbacks like Awake, Start, OnEnable, OnDisable, OnDestroy, and OnValidate (editor only). None of them are triggered when a different component gets attached.
If you need this in the Editor
You can use OnValidate() to detect changes in the Inspector (like checking if the component count increased). But this works only in the editor, not in a built game.
If you need this at Runtime
Unity does not notify other components when one is added. The only reliable solution is to control how components are added. For example:
Create a helper method that adds components.
After adding the component, manually notify other components on the GameObject.
Or have the newly added component register itself in Awake().
Professional takeaway
In real-world Unity projects, this is usually handled by:
A factory/helper method for adding components
A manager system
Or self-registration in Awake()
Unity simply doesn’t support automatic cross-component “component added” events. You have to design around it.
