why OnBecameVisible doesn't work?

Unity Engine
1

the lines of code that are inside of the OnBecameVisible method doesn’t work at all, why?

using UnityEngine;
using System.Collections;

public class EnemyScript : MonoBehaviour {

    private Transform EnemyTransform01;

    public float Enemy01MaxSpeed = 40f;

    public float Enemy01MinSpeed = 10f;

    private float CurrentXsDirection1 = 1;

    private float CurrentXsDirection2 = 4;
   

    // Use this for initialization
    void Start () {
        EnemyTransform01 = transform;
    }
   
    // Update is called once per frame
    void Update () {
        EnemyTransform01.Translate (Vector3.forward * Random.Range (Enemy01MinSpeed, Enemy01MaxSpeed) * Time.deltaTime);
        if (EnemyTransform01.position.z >= 0) {
            Destroy (this.gameObject);
                }
    }
    void OnBecameVisible() {
        float XtimerDirection = 4f;
        EnemyTransform01.Translate (Vector3.left * Random.Range (Enemy01MinSpeed, Enemy01MaxSpeed) * Time.deltaTime);
        XtimerDirection -= Time.deltaTime;
        if (XtimerDirection <= 2) {
            XtimerDirection = 4f;
        };
        if (XtimerDirection <= 3) {
        EnemyTransform01.Translate (Random.Range (CurrentXsDirection1, CurrentXsDirection2), 0, 0 * Time.deltaTime);
        };
        if (XtimerDirection <= 2.5) {
        EnemyTransform01.Translate (-Random.Range (CurrentXsDirection1, CurrentXsDirection2), 0, 0 * Time.deltaTime);
        };   
    }
    void OnTriggerEnter (Collider enemycollider)
    {
        if (enemycollider.CompareTag("PlayerWeapon"))
        {
            Destroy(this.gameObject);
        }
  }
}
2

I’m not 100% but I believe OnBecomeVisible isn’t an updated function. I think it get’s called once, you need to use Update() and then have a bool flag to say that the object is visible, then run that inside of Update.

bool isVisible;
void OnBecomeVisible(){
isVisible = true;
}
void OnBecomeInvisible(){
isVisible = false;
}

void Update()
{
if(isVisible)
{
// run code
}
}