RangeChecker

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

public class RangeChecker : MonoBehaviour {
    //A list of tags to check for
    public List<string> tags;
    //List of targets that is generated when we check for what has what tags
    List<GameObject> m_targets = new List<GameObject>();
    //When something enters the collider
    private void OnTriggerEnter(Collider other)
    {
        //When something enters the trigger set it as not a valid target instead of assuming that it is valid
        bool invalid = true;

        for (int i = 0; i < tags.Count; i++)
        {
            //Check if it has any of the tags from our list if so move on to the line where it adds the object to our valid target list
            if (other.CompareTag(tags[i]))
            {
                invalid = false;
                break;
            }
        }
        //If it is still invalid move on and wait for new objects to enter
        if (invalid)
        {
            return;
        }
        m_targets.Add(other.gameObject);
    }
    //When it exits the collider
    private void OnTriggerExit(Collider other)
    {
        for (int i = 0; i < m_targets.Count; i++)
        {
            //If the object leaving is a target remove it from the target list
            if (other.gameObject == m_targets[i])
            {
                m_targets.Remove(other.gameObject);
                return;
            }
        }
    }
    //When we say GetValidTargets we mean set the list of valid targets to the current list of targets
    public List<GameObject> GetValidTargets()
    {
        for (int i = 0; i < m_targets.Count; i++)
        {
            if (m_targets[i] == null)
            {
                m_targets.RemoveAt(i); i--;
            }
        }
        return m_targets;
    }
    public bool InRange(GameObject go)
    {
        //For each object inrange check if it is in the list of valid targets
        for (int i = 0; i < m_targets.Count; i++)
        {
            if (go == m_targets[i])
            {
                //If so then return the value to be true
                return true;
            }
        }
        //Otherwise it's false
        return false;
    }
}