Instantiate gets called every frame and doesn't wait for timer

Questions & Answers
1

Hey,
I want to Instantiate a bullet every 2 seconds or so but it gets called every frame even though I set an interval. What’s wrong with my code?

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

public class Tower : MonoBehaviour
{
    GameObject[] enemyList;
    float attackRange = 5f;
    GameObject nearestEnemy;
    GameObject bulletPrefab;
    float attackInterval = 2f;
    float nextAttack = 0f;

    void Start()
    {
        bulletPrefab = Resources.Load<GameObject>("Prefabs/BulletPrefab");
    }

    void Update()
    {
        findNearestEnemy();
        if (nextAttack <= 0)
        {
            nextAttack = attackInterval;
            if (nearestEnemy != null)
            {
                if (Vector2.Distance(nearestEnemy.transform.position, transform.position) <= attackRange)
                {
                    Instantiate(bulletPrefab, transform.position, Quaternion.identity);
                    nearestEnemy = null;
                }
            }
        }
        else
        {
            nextAttack -= Time.deltaTime;
        }
    }

    void findNearestEnemy()
    {
        enemyList = GameObject.FindGameObjectsWithTag("Enemy");
        if (enemyList.Length != 0)
        {    
            float minDist = Mathf.Infinity;
            foreach (var enemy in enemyList)
            {
                float dist = Vector2.Distance(transform.position, enemy.transform.position);
                if (dist < minDist)
                {
                    nearestEnemy = enemy;
                }
            }
        }
    }
}
2

1). You never actually set or reset your nextAttack it is always <= 0, after instantiate reset it to 2f

2). You have a lot of inefficiency in your method. (calling FindGameObjectsWithTag every frame)

You should consider caching your enemies.