How do I start a Coroutine without having an instance of the script?

Questions & Answers
1

Hello! I’m trying to start a coroutine in a static void which is in a non-instantiated script. Once i try to call the void I get a NullReferenceException at line 12. Can anyone help me solve this issue?

Here is my code:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;
using Game.Effects;

    public class SceneLoader : MonoBehaviour
    {
        public static void LoadSceneByName(string sceneName, float fadeOutLength = 0f, float fadeInLength = 0f)
    {
        MonoBehaviour mono = new MonoBehaviour();
        mono.StartCoroutine(LoadScene_Num(SceneManager.GetSceneByName(sceneName).buildIndex, fadeOutLength, fadeInLength));
    }

    static IEnumerator LoadScene_Num(int sceneIndex, float fadeOutLength, float fadeInLength)
    {
        Effects.DoFade(fadeOutLength, FadeType.FadeOut);

        yield return new WaitForSeconds(fadeOutLength);
        AsyncOperation operation = SceneManager.LoadSceneAsync(sceneIndex);

        yield return operation.isDone;
        Effects.DoFade(fadeInLength, FadeType.FadeIn);
    }
}
2

Since SceneLoader inherits from MonoBehaviour, take advantage of it

using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 using Game.Effects;
 public class SceneLoader : MonoBehaviour
 {
      private SceneLoader instance;
      public SceneLoader Instance
      {
           get
           {
                if( instance == null )
                {
                     instance = new GameObject("SceneLoader").AddComponent<SceneLoader>();
                }
                return instance;
           }
      }

     public static void LoadSceneByName(string sceneName, float fadeOutLength = 0f, float fadeInLength = 0f)
     {
         Instance.StartCoroutine(Instance.LoadScene_Num(SceneManager.GetSceneByName(sceneName).buildIndex, fadeOutLength, fadeInLength));
     }
     private IEnumerator LoadScene_Num(int sceneIndex, float fadeOutLength, float fadeInLength)
     {
         Effects.DoFade(fadeOutLength, FadeType.FadeOut);
         yield return new WaitForSeconds(fadeOutLength);
         AsyncOperation operation = SceneManager.LoadSceneAsync(sceneIndex);
         yield return operation.isDone;
         Effects.DoFade(fadeInLength, FadeType.FadeIn);
     }
 }