Inheriting functions like Start or Update

EDIT: Sorry, this should have been posted to Scripting, please move it.

Wanted to know if there was a best practice for chaining functions like Start or Update. It seems to me like they should be virtual. The following situation produces a warning.

Code (csharp):

1.  
2. class A : MonoBehaviour
3. {
4.   void Start()
5.   {
6.      //DoSomething
7.   }
8. }
9.  
10. class B : A
11. {
12.   void Start()
13.   {
14.     base.Start();
15.     //DoSomethingElse
16.   }
17. }
18.  

Specifying B::Start as an override function doesn't work because it's not virtual. I suppose the only valid option to remove the warning is to specify it as a new function. That doesn't prevent base.Start() from doing its job, but is there a Unity sanctioned way to deal with inheritance w.r.t. Unity event hooks?

Thanks,
Factoid

 

We usually just do our own functions -- OnStart or OnAwake -- but in general we're able to avoid it altogether. You're usually better off with a component-based design versus class hierarchies.

 

Usually I agree. We make heavy use of component architecture, but in this instance we have components that are looking for "Weapons" to act upon, and we have some weapons which share base code, but implement some actions differently. Our previous component solution degenerated into a mess of SendMessage calls and case specific logic.

We use components everywhere we have a 'has a' relationship, but when it's an 'is a' relationship, anything other than inheritance is a PITA.

 

You can just make your base class method virtual and use override on the derived class method and everything will work work as expected. It works correctly with Unity events such as Start as well as with SendMessage and the like.

 

So even though MonoBehaviour::Start() isn't virtual, I can redefine it as virtual in a derived class? Thanks for the tip, I'll give that a whirl.

 

In fact, MonoBehaviour doesn't define Start or any of the other event methods at all. They're not part of its interface. Instead, when you implement Start in your class, you're actually providing the base class implementation and you're free to make it virtual if you want to. This works because Unity uses reflection to look up these special methods by name and signature instead of by calling them through a predefined interface.

 

That would explain why they suggest not implementing those functions if they don't do anything. Thanks again for the clarification.