Unity ECS Baker中如何标记struct为unmanaged消除Rider误报？

我使用Unity 2022.2.0b16和最新版Rider，基于com.unity.entities包编写了如下Baker代码：

public class LevelBaker : Baker<LevelMono>
{
    public override void Bake(LevelMono authoring)
    {
        AddComponent(new LevelProperties
        {
            SpawnDimensions = authoring.SpawnDimensions,
            NeutralSpawnCount = authoring.NeutralSpawnCount,
            NeutralActorPrefab = GetEntity(authoring.NeutralActorPrefab)
        });
        AddComponent(new LevelRandom
        {
            Value = Random.CreateFromIndex(authoring.RandomSeed)
        });
    }
}

代码可正常编译运行，但Rider高亮AddComponent方法并提示错误：

The type 'ComponentsAndTags.LevelProperties' must be valid unmanaged type (simple numeric, 'bool', 'char', 'void', enumeration type or non-generic struct type with all fields of unmanaged types at any level of nesting) in order to use it as a type argument for 'T' parameter

AddComponent方法的泛型约束为：

public void AddComponent<T>(in T component) where T : unmanaged, IComponentData

我的LevelProperties是仅包含unmanaged类型的struct：

public struct LevelProperties : IComponentData
{
    public float2 SpawnDimensions;
    public int NeutralSpawnCount;
    public Entity NeutralActorPrefab;
}

解决方法 #

• 添加结构布局属性：给LevelProperties加上[StructLayout(LayoutKind.Sequential)]属性，强制struct按顺序布局，帮助Rider识别其为unmanaged类型：

  using System.Runtime.InteropServices;
  using Unity.Entities;
  using Unity.Mathematics;
  
  [StructLayout(LayoutKind.Sequential)]
  public struct LevelProperties : IComponentData
  {
      public float2 SpawnDimensions;
      public int NeutralSpawnCount;
      public Entity NeutralActorPrefab;
  }
  

• 使用readonly struct修饰：将struct声明为readonly struct，C#中该类型若所有字段均为unmanaged，会更明确地被识别为unmanaged类型：

  public readonly struct LevelProperties : IComponentData
  {
      public readonly float2 SpawnDimensions;
      public readonly int NeutralSpawnCount;
      public readonly Entity NeutralActorPrefab;
  }
  

• 清除Rider缓存并重新索引：

  1. 打开Rider的File菜单，选择Invalidate Caches...
  2. 勾选所有缓存选项，点击Invalidate and Restart
  3. 重启后等待Rider重新完成Unity项目索引

• 确认依赖类型的命名空间：确保float2来自Unity.Mathematics、Entity来自Unity.Entities，避免因命名空间错误导致Rider无法识别类型的unmanaged属性。

内容的提问来源于stack exchange，提问作者Arkadiusz Galler