Destroy prefabs after they have been instantiated (C#)

Questions & Answers
1

Hello my friend who is reading this! I got a problem with some of my code. I have created a power up prefab that is supposed to destroy all enemy prefabs that are out on the map. I’m spawning out new enemies every 3 to 5 seconds. Now when I run over the power up, it only destroys the enemies that were instantiated before the power up was used and spawned.

How can I destroy all enemies out on the map including the new ones that spawned in after the power up spawns in?

Code for picking up the power up: (Note that the power up is used directly when you trigger/collide with it)

using UnityEngine;
using System.Collections;

public class PickUpScript : MonoBehaviour 
{
	void OnTriggerEnter2D(Collider2D col)
	{
		if(col.gameObject.tag == "PowerUp1")
		{
			Destroy(GameObject.FindGameObjectWithTag("EnemyBouncing"));
			Destroy(GameObject.FindGameObjectWithTag("EnemyFollow"));
			Destroy(GameObject.FindGameObjectWithTag("PowerUp1"));
		}
}

Code for spawning out enemies:

using UnityEngine;
using System.Collections;

public class EnemySpawn : MonoBehaviour 
{
	// EnemyPrefabs
	public GameObject EnemyBouncingPrefab;
	public GameObject EnemyFollowPrefab; 

	//Show where spawn is prefab
	public GameObject ShowEnemySpawn;

	// Array of spawn points 
	public Transform[] spawnPoints;         
	
	// Borders
	public Transform borderTop;
	public Transform borderBottom;
	public Transform borderLeft;
	public Transform borderRight;



	void Start () 
	{
		// Starts a coroutine function for spawning bouncing enemies
		StartCoroutine(SpawnBouncingEnemy());

		// Spawn only one follow enemy
		InvokeRepeating("SpawnEnemyFollow", Random.Range(2, 5), 0);
	}

	
	// Spawn a Bouncing enemy
	IEnumerator SpawnBouncingEnemy() 
	{
		//Wait 3 seconds when game starts to spawn a ball
		yield return new WaitForSeconds(Random.Range(3, 5));

		while(true)
		{
			//Calls the function to set random position
			Vector2 spawnPoint = RandomPointWithinBorders();
			
			// Show spawn location for one second
			Object marker = Instantiate(ShowEnemySpawn, spawnPoint, Quaternion.identity);
			yield return new WaitForSeconds(1);
			Destroy(marker);
			
			// Spawn enemy
			Instantiate(EnemyBouncingPrefab, spawnPoint, Quaternion.identity);
			yield return new WaitForSeconds(Random.Range(4, 6));
		}
		
	}	

	Vector2 RandomPointWithinBorders()
	{
		//Code that will spawn a bouncing ball and ShowSpawn at a random position inside the borders 
		Vector2 random = new Vector2();
		random.x = (int)Random.Range(borderLeft.position.x, borderRight.position.x);
		random.y = (int)Random.Range(borderBottom.position.y, borderTop.position.y);
		return random;
	}


	void SpawnEnemyFollow()
	{
		// Find a random index between zero and one less than the number of spawn points.
		int spawnPointIndex = Random.Range (0, spawnPoints.Length);

		
		// Create an instance of the enemy prefab at the randomly selected spawn point's position and rotation.
		Instantiate (EnemyFollowPrefab, spawnPoints[spawnPointIndex].position, spawnPoints[spawnPointIndex].rotation);
	}
}

I’m so grateful for every help that I can get! You guys are the best! Been trying to solve this for ages, but haven’t found any great answers yet.

2

Instead of using the tag system, you might want to just keep track of your spawned enemies:

using System.Collections.Generic;

So we’ll just add new enemies to a list:

// Keep track of enemies we've created across all spawners
public static List<GameObject> activeEnemies;

// Start
void Awake()
{
	// Create the list
	activeEnemies = new List<GameObject>();
}

// Destroy all existing enemies
public static void DestroyActiveEnemies()
{
	// Prevent ourselves from tinkering with a List during its enumeration
	int currentCount = activeEnemies.Count;

	// Go through and destroy each one
	for (int k=0; k<currentCount; k++)
	{
		Destroy(activeEnemies[k]);
	}

	// Clear the list up to this point
	activeEnemies.RemoveRange(0, currentCount);
}

So for each of your spawning functions, add the new enemy to this list:

// Instantiate
GameObject newEnemy = (GameObject) Instantiate(EnemyBouncingPrefab, spawnPoint, Quaternion.identity);

// Add them to our list
activeEnemies.Add(newEnemy);

// Yield for the coroutine (Note that this will cause GC (due to the "new" part),
// but you can declare a WaitForSeconds instance to prevent this
yield return new WaitForSeconds(Random.Range(4, 6));

Causing your pickup script’s Trigger code to become:

public class PickUpScript : MonoBehaviour 
{
	void OnTriggerEnter2D(Collider2D col)
	{
		if(col.gameObject.tag == "PowerUp1")
		{		
			// Call the function we just wrote
			EnemySpawn.DestroyActiveEnemies();
		}
	}
}