Noob Inject question

Hello my name is stefana I'm fairly new to ECS. I used an older version of ECS and my code depends on Inject but it's obsolete in the latest version.

The only way I know to get access to other systems data is using inject. I've looked around but I can't figure out how to get data from one system to another anymore.

Thank you for taking time out

 

Code (CSharp):

1.   MySystem m_injectedSystem;
2.   protected override void OnCreate() {
3.     base.OnCreate();
4.     m_injectedSystem = World.GetExistingSystem<MySystem>();
5.   }

 

Thank you! Am I missing something? Is there something better then Entities.ForEach? is Entities.ForEach even performance friendly?

Code (CSharp):

1.         Entities.ForEach((Entity entity, Transform zzz) =>
2.         {
3.             Debug.Log(zzz.name);
4.  
5.  
6.         });

 

Do you know what this error is?

Code (CSharp):

1. Ignoring invalid [UpdateAfter] dependency for NewBehaviourScript: UnityEngine.Experimental.PlayerLoop.FixedUpdate must be a member of the same ComponentSystemGroup.
2.