Damage over time unity

Question

I want to make spell damage over time. So here is my code:

public class Spell : MonoBehaviour
 {
    public float damage = 1.0f;
    public bool ignoreCaster = true;
    public float delayBeforeCasting = 0.4f;
    public float applyEveryNSeconds = 1.0f;
    public int applyDamageNTimes = 5;

    private bool delied = false;

    private int appliedTimes = 0;
    void OnTriggerStay(Collider other)
    {
        IDamageable takeDamage = other.gameObject.GetComponent<IDamageable>();
        if(takeDamage != null)
        {
            StartCoroutine(CastDamage(takeDamage));
        }
    }

    IEnumerator CastDamage(IDamageable damageable)
    {
        if(!delied)
        {
            yield return new WaitForSeconds(delayBeforeCasting);
            delied = true;
        }

        while(appliedTimes < applyDamageNTimes)
        {
            damageable.TakeDamage(damage);
            yield return new WaitForSeconds(applyEveryNSeconds);
            appliedTimes++;
        }
    }
}

Problem is where while starts. I want to check if appliedTimes < applyDamageNTimes, then if it is true to do damage, wait for delay (applyEveryNSeconds) and then check again but i am not handy with coroutine and for some reason it is not doing that.

Here is working code. Also look for other answers if someone need!

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

public class Spell : MonoBehaviour
{
    public float damage = 1.0f;
    public bool ignoreCaster = true;
    public float delayBeforeCasting = 0.0f;
    public float applyEveryNSeconds = 1.0f;
    public int applyDamageNTimes = 1;

    private bool delied = false;

    private int appliedTimes = 0;

    private bool test = false;
    void OnTriggerStay(Collider other)
    {
        IDamageable takeDamage = other.gameObject.GetComponent<IDamageable>();
        if(takeDamage != null)
        {
            StartCoroutine(CastDamage(takeDamage));
        }
    }

    IEnumerator CastDamage(IDamageable damageable)
    {
        if(!test && appliedTimes <= applyDamageNTimes || !test && applyEveryNSeconds == 0)
        {
            test = true;
            if(!delied)
            {
                yield return new WaitForSeconds(delayBeforeCasting);
                delied = true;
            }
            else
            {
                yield return new WaitForSeconds(applyEveryNSeconds);
            }
            damageable.TakeDamage(damage);
            appliedTimes++;
            test = false;
        }
    }
}

Answer 1

OnTriggerStay is called every frame 2 objects are colliding. This means that an asynchronous instance of CastDamage coroutine is called every frame. So what happens is that you're getting a whole lot of damage per seconds, which simulates not any damage per second, hehe.

So change OnTriggerStay to OnTriggerEnter.

Depending on the kind of spell it is, I'd rather create a DPS script and apply that to the game object so...

• Spell hits Object
• AddComponent< MyDamageSpell>();

And then the MyDpsSpell does damage every N seconds to the Object it's on, and removes itself when it is done:

// Spell.cs

void OnTriggerEnter(Collider col) {
    // if you don't want more than 1 dps instance on an object, otherwise remove if
    if (col.GetComponent<MyDpsAbility>() == null) {
        var dps = col.AddComponent<MyDpsAbility>();
        dps.Damage = 10f;
        dps.ApplyEveryNSeconds(1);
        // and set the rest of the public variables
    }
}

// MyDpsAbility.cs

public float Damage { get; set; }
public float Seconds { get; set; }
public float Delay { get; set; }
public float ApplyDamageNTimes { get; set; }
public float ApplyEveryNSeconds { get; set; }

private int appliedTimes = 0;

void Start() {
    StartCoroutine(Dps());
}

IEnumerator Dps() {
    yield return new WaitForSeconds(Delay);

    while(appliedTimes < ApplyDamageNTimes)
    {
        damageable.TakeDamage(damage);
        yield return new WaitForSeconds(ApplyEveryNSeconds);
        appliedTimes++;
    }

    Destroy(this);
}

If it's an aura spell where units take damage every second they're in range you could do something like:

float radius = 10f;
float damage = 10f;
void Start() {
    InvokeRepeating("Dps", 1);
}


void Dps() {
    // QueryTriggerInteraction.Collide might be needed
    Collider[] hitColliders = Physics.OverlapSphere(gameObject.position, radius);

    foreach(Collider col in hitColliders) {
        col.getComponent<IDamagable>().TakeDamage(10);
    }
}

https://docs.unity3d.com/ScriptReference/Physics.OverlapSphere.html

Answer 2

Why not create, instead a system that applies auras to in-game characters? For example, if a spell like this adds a damage over time debuff it could instead add the debuff-aura script to the game object and then remove itself once its conditions are met.