Unity代码报错CS1061求助：Collider2D[]无length定义

原问题代码： #

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Collidable : MonoBehaviour
{
    public ContactFilter2D filter;
    private BoxCollider2D boxCollider;
    private Collider2D[] hits = new Collider2D[10];

    protected virtual void Start()
    {
        boxCollider = GetComponent<BoxCollider2D>();
    }

    protected virtual void update()
    {
        // Collision work
        boxCollider.OverlapCollider(filter, hits);
        for (int i = 0; i < hits.length; i++)
        {
            if (hits[i] == null)
                continue;

            Debug.Log(hits[i].name);

            // The array is not cleaned up, so we do it ourself
            hits[i] = null;
        }
    }
}

报错信息： #

error CS1061: 'Collider2D[]' does not contain a definition for 'length' and no accessible extension method 'length' accepting a first argument of type 'Collider2D[]' could be found (are you missing a using directive or an assembly reference?)

修复要点： #

• 数组长度属性大小写错误：C#中数组的长度属性是Length（首字母大写），不是小写的length，这是触发报错的直接原因。
• Update方法名大小写错误：Unity MonoBehaviour的帧更新方法必须是大写的Update，小写的update不会被Unity自动调用，你的碰撞检测逻辑根本不会执行。
• 优化遍历效率：boxCollider.OverlapCollider会返回实际检测到的碰撞体数量，用这个返回值来遍历数组，不用循环整个数组的10个元素，避免无效的空值判断。

修复后完整代码： #

using System.Collections;
using System.Collections;
using UnityEngine;

public class Collidable : MonoBehaviour
{
    public ContactFilter2D filter;
    private BoxCollider2D boxCollider;
    private Collider2D[] hits = new Collider2D[10];

    protected virtual void Start()
    {
        boxCollider = GetComponent<BoxCollider2D>();
    }

    protected virtual void Update()
    {
        // 获取实际碰撞到的数量
        int hitCount = boxCollider.OverlapCollider(filter, hits);
        
        for (int i = 0; i < hitCount; i++)
        {
            Debug.Log(hits[i].name);

            // 清空当前元素，避免下一帧残留
            hits[i] = null;
        }
    }
}

内容的提问来源于stack exchange，提问作者Niks Rodžers