Entitas learning [iv] other common knowledge points

EntityIndex

[Game, Input, UI]
public class NumberComponent : IComponent
{
    
    [EntityIndex]
    public int number;
}

It is written as follows , When an attribute of a component has this tag ,Entitas When generating code based on components, the method to find based on this property will be generated , In a specified context , This attribute can be used as a unique id, Find the exact entity based on this .
It doesn't have to be int type ,string And so on.

Contexts.sharedInstance.game.GetEntitiesWithNumber(666);

The above code works everywhere , Even in monobehaviour In the script , But it is not recommended to access outside the framework Entitas Things inside .

GetEntitiesWithNumber This function only specifies EntityIndex Properties of will be generated .

public static class ContextsExtensions {
    

    public static System.Collections.Generic.HashSet<GameEntity> GetEntitiesWithNumber(this GameContext context, int number) {
    
        return ((Entitas.EntityIndex<GameEntity, int>)context.GetEntityIndex(Contexts.Number)).GetEntities(number);
    }

    public static System.Collections.Generic.HashSet<InputEntity> GetEntitiesWithNumber(this InputContext context, int number) {
    
        return ((Entitas.EntityIndex<InputEntity, int>)context.GetEntityIndex(Contexts.Number)).GetEntities(number);
    }

    public static System.Collections.Generic.HashSet<UIEntity> GetEntitiesWithNumber(this UIContext context, int number) {
    
        return ((Entitas.EntityIndex<UIEntity, int>)context.GetEntityIndex(Contexts.Number)).GetEntities(number);
    }
}

Event

It is written as follows

[Event(EventTarget.Any, EventType.Added)]
public class NumberComponent : IComponent
{
    
    [EntityIndex]
    public int number;
}

In the use of the Event after , The generated code will be in this folder .

One of the

public interface IAnyNumberListener {
    
    void OnAnyNumber(GameEntity entity, int number);
}

Inherit this interface rewrite OnAnyNumber Method ,
When NumberComponent When a component is added or deleted
Will be called back , When calling back, the value and entity of the component are passed in .

EventTarget There are two kinds of ,Any and Self

• The tag Any Of , All inherited IAnyNumberListener Of OnAnyNumber Will be called back , Not limited to Entitas Class .
• The tag Self Of , Only inheritance is limited IAnyNumberListener With NumberComponent The entity class of the component will be notified , So this kind of writing , We also need to be in our own script , Redefine the correlation by distributing classes context Below Entity, Let him inherit IAnyNumberListener Rewrite method .

Parameters EventType There are two options

  public enum EventType
  {
    
    Added,
    Removed,
  }

Specify to call when the component is added or deleted

In fact, this label is added ,Entitas Will automatically generate a reaction system

public sealed class AnyNumberEventSystem : Entitas.ReactiveSystem<GameEntity> {
    

    readonly Entitas.IGroup<GameEntity> _listeners;
    readonly System.Collections.Generic.List<GameEntity> _entityBuffer;
    readonly System.Collections.Generic.List<IAnyNumberListener> _listenerBuffer;

    public AnyNumberEventSystem(Contexts contexts) : base(contexts.game) {
    
        _listeners = contexts.game.GetGroup(GameMatcher.AnyNumberListener);
        _entityBuffer = new System.Collections.Generic.List<GameEntity>();
        _listenerBuffer = new System.Collections.Generic.List<IAnyNumberListener>();
    }

    protected override Entitas.ICollector<GameEntity> GetTrigger(Entitas.IContext<GameEntity> context) {
    
        return Entitas.CollectorContextExtension.CreateCollector(
            context, Entitas.TriggerOnEventMatcherExtension.Added(GameMatcher.Number)
        );
    }

    protected override bool Filter(GameEntity entity) {
    
        return entity.hasNumber;
    }

    protected override void Execute(System.Collections.Generic.List<GameEntity> entities) {
    
        foreach (var e in entities) {
    
            var component = e.number;
            foreach (var listenerEntity in _listeners.GetEntities(_entityBuffer)) {
    
                _listenerBuffer.Clear();
                _listenerBuffer.AddRange(listenerEntity.anyNumberListener.value);
                foreach (var listener in _listenerBuffer) {
    
                    listener.OnAnyNumber(e, component.number);
                }
            }
        }
    }
}

Different systems that generate different tags can change the tags themselves and then go in to see what is different .
The difference between different labels I mentioned above can be verified in this way .

Next, it will be recorded with Entitas Record Endless ball Key points of the case .

other

Adding Feature When , Different Feature The addition order of Feature Inside System The order of execution is influential , Therefore, when doing more in-depth, you should clarify when adding Feature Between the execution sequence of their own to do System The impact of the order of execution , That is, if two System Of Trigger identical , Then if two System When the execution order will affect the result , Consider two System Of Feature The order in which they are added , See if you want to belong Feature Changes . If Feature identical , Consider two System In this Feature The order in which they are added .

Reference resources

Unity Framework exploration ——ECS framework Entitas The basic concept of this chapter

EntityComponentSystem framework Entitas Multi context response system （ Four ）