Question Using interfaces for "dealing damage"

I am fairly new to unity (and programming in general) and started building a small game/demo for android.
I have been following a tutorial to implement a damage system which contains hitbox-detection (via overlap)
.
In the last step an interface is implemented and I thought for a whole while that this interface is for all the objects that can be hit by the hitbox and receive damage. But after a lot of trouble I finally understood, that this interface is for those classes that use the hitbox.

After realising that, I still didnt know how to tell the enemies that were hit by the hitbox to take damage. It seemed intuitive for me to use an interface for that but I could not make it work. After one day of trying and reading about interfaces I gave up and went like this:

For context:

Code (CSharp):

1. public class Attack              
2. {
3.     public bool success = false;                                   //Some enemie hit
4.     public Collider2D[] targets = new Collider2D[5];  
5.     public int hitEnemies;                                              //how many enemies are hit?
6. }

in the managerscript:

Code (CSharp):

1.             for (int i = 0; i < playerAttack.hitEnemies; i++)
2.             {
3.                 Collider2D aCollider = playerAttack.targets[i];
4.                 aCollider.GetComponent<Enemy>().takeDamage(10);
5.             }

This solution works. For now there only is one enemy, so thats no problem.
But will this be a problem if there are more enemies? By my understanding every future enemy I plan on implementing would need to have the same <Enemy> - script as a component to reuse my hitbox-script. But what if I want future enemies to move differently for example? Is the solution to use different scripts on my gameObjects (in this case enemies): One for receiving damage, one for moving etc. ?
Lets say I have my enemy and he has the "Moving" script and the "hurtbox" script. Future enemies would use the hurtbox-script as well then but would need different values for health, defense maybe... So the solutions of a interface seems good: every hurtbox of the different enemies will just have to implement a common core and have its own other values which can still be different. Is that the "right" way?

But how do I reference that common core in my manager then?

I also read that "GetComponent" is quite expensive as a method (which is bad because I program the demo for mobile) and that one can use interfaces... But how? Im sorry that I cannot really be more precise about my questions regarding interfaces, I just cannot really wrap my head around them.


For more context, the tutorial I followed is that one:
https://www.gamasutra.com/blogs/NahuelGladstein/20180514/318031/Hitboxes_and_Hurtboxes_in_Unity.php
I did not really understand the last parts in which the interface is implemented.


Thanks alot in advance for your time and help

 

You can use GetComponent<IMyInterface> and it will just work. Do not worry about performance till it becomes a problem. You could have an interface called IDamageReceiver or something and have any number of scripts implementing it. Or you could just have a base class for all of them and use GetComponent<BaseClass>.

 

You can have a lookup for example Dictionary<Collider, IMyInterface>.

 

I wouldn't bother till it becomes an issue though. Always keep your code as simple as possible, saves you debugging time.

 

In that case, would I have for example:

IDamageReceiver {takeDamage(int)}

gameObject enemy1
with components: (script1: IDamageReceiver), (Script2)...

gameObject enemy2
with components: (script3: IDamageReceiver), (Script4)...

and change my code to:

Code (CSharp):

1.                 for (int i = 0; i < playerAttack.hitEnemies; i++)
2.                 {
3.                     Collider2D aCollider = playerAttack.targets[i];
4.                     aCollider.GetComponent<IDamageReceiver>().takeDamage(10);
5.                 }
6.  

?


Thanks for the help and the tip not to worry too much about performance + I will look into Dictionarys as I have not worked with them before.
I will try the ideas and come back here if new problems arise.

 

Interfaces are just a way to call methods on an unknown Type. It lets you not care if its an 'Enemy' or a 'Vehicle', so long as it's an IMove.

You can use components in a similar way, except the component will have the same code for Enemy and Vehicle, so you will have to subclass it, or use events.

• Move : MonoBehaviour
  • MoveThisWay : Move
  • MoveAnotherWay : Move

Now if you attach the MoveThisWay component,

GetComponent<Move>()

will be able to use the subclasses' overridden movement function instead.

Or Move can just call a

UnityEvent<Vector3> OnMove

event, then you can call any function from any component that has a Vector3 parameter.

Basically, yes. This is a more compositional approach, but there are many ways to do it.

 

Yes to everything. script1 and script3 in your example would be classes inheriting MonoBehaviour and implementing IDamageReceiver. When I can I prefer working with interfaces because they are easier to test and also make the code clearer IMHO.