1.不能在Job中执行的操作

2.EntityCommandBufferSystem

3.BeginInitializationEntityCommandBufferSystem

using Unity.Collections;
using Unity.Entities;
using Unity.Jobs;
using Unity.Transforms;

public class SpawnerSystem_FromEntity : JobComponentSystem
{
    BeginInitializationEntityCommandBufferSystem m_EntityCommandBufferSystem;

    protected override void OnCreate ()
    {
        /* 在OnCreate函数里获取或创建BeginInitializationEntityCommandBufferSystem */
        m_EntityCommandBufferSystem = World.GetOrCreateSystem<BeginInitializationEntityCommandBufferSystem>();
    }

    protected override JobHandle OnUpdate (JobHandle inputDeps) { }
}

    protected override JobHandle OnUpdate (JobHandle inputDeps)
    {
        /* 相当于获取了队列 */
        var commandBuffer = m_EntityCommandBufferSystem.CreateCommandBuffer().ToConcurrent();

        var jobHandle = Entities
            .ForEach((Entity entity, int entityInQueryIndex, in Spawner_FromEntity spawnerFromEntity) =>
            {
                /* 在Buffer中创建实体 */
                var instance = commandBuffer.Instantiate(entityInQueryIndex, spawnerFromEntity.Prefab);

                /* 删除筛选出来的实体对象，这个很重要，后面会解释 */
                commandBuffer.DestroyEntity(entityInQueryIndex, entity);
            }).Schedule(inputDeps);

        /* 把Job添加到EntityCommandBufferSystem */
        m_EntityCommandBufferSystem.AddJobHandleForProducer(jobHandle);

        return jobHandle;
    }

4.细节解释

5.Job会被无限添加吗？

6.另一种创建实体的方式

using Unity.Entities;

public struct Spawner_FromEntity : IComponentData
{
    public Entity Prefab;
}

using System.Collections.Generic;
using Unity.Entities;
using UnityEngine;

[RequiresEntityConversion]
public class SpawnerAuthoring_FromEntity : MonoBehaviour, IDeclareReferencedPrefabs, IConvertGameObjectToEntity
{
    public GameObject Prefab;

    // Referenced prefabs have to be declared so that the conversion system knows about them ahead of time
    public void DeclareReferencedPrefabs (List<GameObject> referencedPrefabs)
    {
        referencedPrefabs.Add(Prefab);
    }

    // Lets you convert the editor data representation to the entity optimal runtime representation
    public void Convert (Entity entity, EntityManager dstManager, GameObjectConversionSystem conversionSystem)
    {
        var spawnerData = new Spawner_FromEntity
        {
            // The referenced prefab will be converted due to DeclareReferencedPrefabs.
            // So here we simply map the game object to an entity reference to that prefab.
            Prefab = conversionSystem.GetPrimaryEntity(Prefab),
        };
        dstManager.AddComponentData(entity, spawnerData);
    }
}

7.这种创建实体的方式有什么优势？