RequireForUpdateの例

DistanceCheckSystem.cs

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

public class DistanceCheckSystem : ComponentSystem
{
    ComponentGroup itemGroup, aiGroup;

    protected override void OnCreateManager()
    {
        base.OnCreateManager();

        itemGroup = GetComponentGroup(ComponentType.ReadOnly<Item>(), ComponentType.ReadOnly<Translation>());
        aiGroup = GetComponentGroup( ComponentType.ReadOnly<AI>(), ComponentType.ReadOnly<Translation>());

        //グループが揃わなければ動作しないようにする
        RequireForUpdate(itemGroup);
        RequireForUpdate(aiGroup);
    }

    protected override void OnUpdate()
    {
        // 複数のComponentGroupをまたぐのでForEachではなくToComponentDataArrayを使う
        var itemPositions = itemGroup.ToComponentDataArray<Translation>(Allocator.TempJob);
        var aiPositions = aiGroup.ToComponentDataArray<Translation>(Allocator.TempJob);

        for(int aiIndex =0; aiIndex < aiPositions.Length; aiIndex++)
        {
            for(int itemIndex = 0; itemIndex < itemPositions.Length; itemIndex++)
            {
                var distance = math.distance(aiPositions[aiIndex].Value, itemPositions[itemIndex].Value);
                if (distance < 1)
                {
                    Debug.Log($"{distance} find item. {distance}");
                    continue;
                }
            }
        }

        itemPositions.Dispose();
        aiPositions.Dispose();
    }
}