HelloCube：IJobForEach

此示例演示了基于作业的ECS系统，该系统可旋转一对立方体。

它显示了什么？

此示例基于ForEach示例构建，并说明如何在多线程作业中执行相同的工作，而不是在主线程上执行相同的工作。

与前面的示例一样，RotationSpeedSystem_IJobForEach 使用存储在RotationSpeed_IJobForEach组件中的数据更新对象的旋转。

JobComponentSystems和IJobForEach

使用IJobForEach的系统是您可以用来处理组件数据的最简单，最有效的方法。对于您设计的任何系统，我们建议从此方法开始。

在此示例中，RotationSpeedSystem_IJobForEach实现为JobComponentSystem。该类创建一个IJobForEach结构来定义需要完成的工作。此作业计划在System的OnUpdate()函数中。

using Unity.Burst;
using Unity.Collections;
using Unity.Entities;
using Unity.Jobs;
using Unity.Mathematics;
using Unity.Transforms;
using UnityEngine;

// This system updates all entities in the scene with both a RotationSpeed_IJobForEach and Rotation component.
public class RotationSpeedSystem_IJobForEach : JobComponentSystem
{
     // Use the [BurstCompile] attribute to compile a job with Burst. You may see significant speed ups, so try it!
     [BurstCompile]
     struct RotationSpeedJob : IJobForEach<Rotation, RotationSpeed_IJobForEach>
     {
         public float DeltaTime;

        // The [ReadOnly] attribute tells the job scheduler that this job will not write to rotSpeedIJobForEach
         public void Execute(ref Rotation rotation, [ReadOnly] ref RotationSpeed_IJobForEach rotSpeedIJobForEach)
         {
             // Rotate something about its up vector at the speed given by RotationSpeed_IJobForEach.
             rotation.Value = math.mul(math.normalize(rotation.Value), quaternion.AxisAngle(math.up(), rotSpeedIJobForEach.RadiansPerSecond * DeltaTime));
         }
     }

    // OnUpdate runs on the main thread.
     protected override JobHandle OnUpdate(JobHandle inputDependencies)
     {
         var job = new RotationSpeedJob
         {
             DeltaTime = Time.deltaTime
         };

        return job.Schedule(this, inputDependencies);
     }
}