Coroutines In Unity

Coroutines in Unity are used to execute code over time instead of all at once, making them ideal for handling delays, animations, and asynchronous tasks without freezing the game. Unlike normal methods that run completely in one frame, coroutines can spread work over multiple frames.

Runs alongside normal game code
Can wait for seconds, frames, or conditions
Does NOT freeze the game while waiting

Creating a Simple Coroutine

A coroutine returns enumerate and uses yield return to pause.

using System.Collections;
using UnityEngine;
public class Timer : MonoBehaviour
{
    void Start()
    {
        StartCoroutine(WaitAndPrint());
    }
    IEnumerator WaitAndPrint()
    {
        Debug.Log("Waiting starts now");
        yield return new WaitForSeconds(2f);  // Pause for 2 seconds
        Debug.Log("2 seconds have passed");
    }
}

Output:

Coroutines-In-Unity — Coroutines In Unity

StartCoroutine() begins the coroutine. yield return new WaitForSeconds(2f) pauses it for 2 seconds. The game continues running normally during the wait.

Common Yield Instructions

Instruction	Waits for
`yield return null`	One frame
`yield return new WaitForSeconds(2f)`	2 seconds
`yield return new WaitForSecondsRealtime(2f)`	2 seconds (ignores timeScale)
`yield return new WaitForFixedUpdate()`	Next physics frame
`yield return new WaitUntil(() => condition)`	Until condition is true
`yield return new WaitWhile(() => condition)`	While condition is true
`yield return StartCoroutine(Another())`	Another coroutine to finish

Example: Spawning Enemies Every 3 Seconds

using System.Collections;
using UnityEngine;

public class EnemySpawner : MonoBehaviour
{
    public GameObject enemyPrefab;
    void Start()
    {
        StartCoroutine(SpawnLoop());
    }
    IEnumerator SpawnLoop()
    {
        while (true)  // Infinite loop
        {
            Instantiate(enemyPrefab, transform.position, Quaternion.identity);
            yield return new WaitForSeconds(3f);  // Wait 3 seconds
        }
    }
}

Output:

Spawning-Enemies-Using-Coroutine-In-Unity — Spawning Enemies Using Coroutine In Unity

The while loop runs forever. After each spawn, it waits 3 seconds before spawning again.

Stopping Coroutines

public class CoroutineManager : MonoBehaviour
{
    private Coroutine myCoroutine;
    void Start()
    {
        myCoroutine = StartCoroutine(MyLoop());
    }
    public void StopMyLoop()
    {
        if (myCoroutine != null)
        {
            StopCoroutine(myCoroutine);
        }
    }
    public void StopAll()
    {
        StopAllCoroutines();  // Stops all on this script
    }
}

Save the coroutine reference to stop it later. StopAllCoroutines() stops every coroutine on the script.

Coroutine vs Invoke vs Update Timer

Coroutine: Complex timing, waiting conditions, smooth transitions.
Invoke: Simple one-time delay.
Update timer: Frame-by-frame counting.

// Coroutine (best for complex)
StartCoroutine(DoSomething());
// Invoke (simple delay)
Invoke("DoSomething", 2f);
// Update timer (manual)
float timer = 0;
void Update() { timer += Time.deltaTime; if (timer > 2f) DoSomething(); }

Creating a Simple Coroutine

Common Yield Instructions

Example: Spawning Enemies Every 3 Seconds

Stopping Coroutines

Coroutine vs Invoke vs Update Timer

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