How to add variable Type component to entity?

Hi i add same type component to few entities when entities are created.
in my work, add component with switch is fine but i guess its not good performance so i wanna make switch statement before use for statement


This is my origin code

Code (CSharp):

1.                 for (int i = 0; i < Prefabs.lenght; i++)
2.                 {
3.                     Entity instance = CommandBuffer.Instantiate(index, prefabSpawner.Prefab);
4.                     switch (prefabSpawner.unitType)
5.                     {
6.                         case ScriptType.ECS:
7.                             CommandBuffer.AddComponent(index, instance, new Player());
8.                             break;
9.                         case ScriptType.JECS:
10.                             CommandBuffer.AddComponent(index, instance, new Enemy());
11.                             break;
12.                         case ScriptType.JECS2:
13.                             CommandBuffer.AddComponent(index, instance, new Unit());
14.                             break;
15.                         default:
16.                             break;
17.                     }
18.                 }

and i wanna make concept like this

Code (CSharp):

1.                 Type scripttype = typeof(None);
2.                 switch (prefabSpawner.unitType)
3.                 {
4.                     case UnitType.Player:
5.                         scripttype = typeof(Player);
6.                         break;
7.                     case UnitType.Enemy:
8.                         scripttype = typeof(Enemy);
9.                         break;
10.                     case UnitType.Unit:
11.                         scripttype = typeof(Unit);
12.                         break;
13.                     default:
14.                         break;
15.                 }
16.  
17.                 for (int i = 0; i < Prefabs.lenght; i++)
18.                 {
19.                     Entity instance = CommandBuffer.Instantiate(index, prefabSpawner.Prefab);
20.                     CommandBuffer.AddComponent(index, instance, scripttype);
21.                 }

but I got error that

The type 'Type' must be a non-nullable value type in order to use it as parameter 'T' in the generic type or method 'EntityCommandBuffer.Concurrent.AddComponent<T>(int, Entity, T)'

How can i fix it?

 

You need to pass the type into a generic method and then call instantiate from there.
Something like this:

Code (CSharp):

1.     void Instantiate<T>() where T : struct, IComponentData {
2.       for (int i = 0; i < Prefabs.lenght; i++) {
3.         Entity instance = CommandBuffer.Instantiate(index, prefabSpawner.Prefab);
4.         CommandBuffer.AddComponent(index, instance, default(T));
5.       }
6.     }

and then your switch or whatever will look like this:

Code (CSharp):

1.       switch (prefabSpawner.unitType) {
2.         case UnitType.Player:
3.           Instantiate<Player>();
4.           break;
5.         case UnitType.Enemy:
6.           Instantiate<Enemy>();
7.           break;
8.         case UnitType.Unit:
9.           Instantiate<Unit>();
10.           break;
11.         default:
12.           break;
13.       }

 

This is what i need it

Thank you.