循环通过统一游戏对象

Question

I am trying to make a game where the user controls a square and other enemy shapes move toward it. So I thought it would be a good idea to loop through all the gameobjects with the tag Enemy . However I was forced to change a code snippet I found from here , but I then ended up with 2 errors.

---

Cannot Implicitly convert 'Unity.GameObject[]' to 'Unity.GameObject'

and

Error   CS1579  foreach statement cannot operate on variables of type 'GameObject' because 'GameObject' does not contain a public instance definition for 'GetEnumerator'

If anyone could tell me why this is happening or a solution to this I would be very grateful, thanks in advance! Here is my code:

void FixedUpdate()

{
    GameObject objects = GameObject.FindGameObjectsWithTag("Enemy");
    var objectCount = objects.Length;
    foreach (var obj in objects)
    {
        // Move the players accordingly
        //var rb = 
        Vector2 direction = (player.position - transform.position).normalized;
        obj.rigidbody.velocity = direction * moveSpeed;

    }
}

Answer 1

FindGameObjectsWithTag as the name hints returns a GameObject[] .

In order tog et the attached Rigidbody2D use GetComponent<Rigidbody2D>

It should be either GameObject[] or simply var

/*GameObject[]*/ var objects = GameObject.FindGameObjectsWithTag("Enemy");
var objectCount = objects.Length;
foreach (var obj in objects)
{
    // Move the players accordingly
    var rb = obj.GetComponent<Rigidbody2D>()
    Vector2 direction = (player.position - transform.position).normalized;
    rb.velocity = direction * moveSpeed;
}

The second one was just a follow up error since you declared objects as a GameObject which indeed as the error says has no GetEnumerator implementation.

---

In general it is not the best thing to use FindObjectsWithTag repeatedly. I would rather use a pattern with a static list of all existing instances like

// Put this component on your enemy prefabs / objects
public class EnemyController : MonoBehaviour
{
    // every instance registers to and removes itself from here
    private static readonly HashSet<EnemyController> _instances = new HashSet<EnemyController>();
    
    // Readonly property, I would return a new HashSet so nobody on the outside can alter the content
    public static HashSet<EnemyController> Instances => new HashSet<EnemyController>(_instances);

    // If possible already drag the Rigidbody into this slot via the Inspector!
    [SerializedField] private Rigidbody2D rb;

    // public read-only access
    public Rigidbody2D Rb => rb;

    private void Awake()
    {
        if(!rb) rb = GetComponent<Rigidbody2D>();
        _instances.Add(this);
    }


    private void OnDestroy()
    {
        _instances.Remove(this);
    }
}

and then use

var enemies = EnemyControler.Instances;
foreach (var enemy in enemies)
{
    // Move the players accordingly
    Vector2 direction = (player.position - transform.position).normalized;
    enemy.Rb.velocity = direction * moveSpeed;
}

Answer 2

Change GameObject type declaration to var

Or change it to GameObject[] since FindGameObjectsWithTag returns an array of GameObject

Also I wouldnt use FindGameObjectsWithTag its slow. More so in a update method

Answer 3

First off, change GameObject to GameObject[] because FindGameObjectsWithTag returns a GameObject array. Be careful not to confuse it with FindGameObjectWithTag without the s which returns a single GameObject

Secondly, I think it would be best to have a separate Enemy script or something like that and assign them to each enemy rather than using FindGameObjectsWithTag which is very slow.