How to instantiate a prefab only when something is hit, and for some seconds?

Question

How do I instantiate a prefab only when something is hit for a few seconds? I mean, I just need to activate the particle system when something is hit. Now it always runs, even before I hit something. I need it to activate the particle system when something is hit and for 2-3 seconds.

This is what I do now:

public void Shot()
{
    Destroy(gameObject);
    Instantiate(effect, transform.position, transform.rotation);
}

Answer 1

As far as only triggering something when it's "hit", this is usually done via a Collider which triggers a callback when it hits something else, such as OnCollisionEnter https://docs.unity3d.com/ScriptReference/MonoBehaviour.OnCollisionEnter.html

For destroying after a 2-3 second delay I would add a new script to the "effect" prefab that destroys itself after waiting some time:

public class DestroyAfterDelay : MonoBehaviour {
    public float delay;

    IEnumerator Start() {
        yield return new WaitForSeconds( delay );
        GameObject.Destroy( gameObject );
    }
}

Answer 2

Heya :) this is pretty simple, the two ways I like to delay something is either using a coroutine or invoking a method. As for on hit if you want the particles to hit on the body where a bullet hits a person, Raycasting a shot and getting its hit.point will help you with achieving the position of the hit, if it is that u just want the particles to Emmitt at a transform, what u have is fine. As for code: Bare with me im on my phone :p

GameObject yourParticleSystem;

void OnCollisionEnter(Collision col)
{
    //this is for if a bullet hits the player 
    if(col.gameObject.tag == "Bullet")
    {
        StartCoroutine(waitTime(3f));
    }
}

IEnumerator waitTime (float time)
{
    yield return new waitForSeconds (time);
    Instantiate(yourParticleSystem, transform.position, Quaternio.identity);
    // this instantiates your prefab at your transform and its rotation
    //if u dont have play on awake ticked in particles a simple 
    yourParticleSystem.Play(); //will make it play
}

Because you aren't pooling your particles, you don't want to have multiple particle GameObject within the scene, if suggest either pooling ur particles or simple adding a destroy script on your particleSystem Eg:

void Start ()
{
    Destroy(gameObject, 4f) // 4f is just a guess to how long the particles play for
}

Sorry if there are some syntax errors I tried my best on the phone hehe ^.^ hope u understand and it works :)))))