How to access StartCoroutine in a static way

Questions & Answers
1

Hello, I got this small problem. I am using StartCoroutine for a www request but I can't figure a work-around to access it in a static way. Here is a sample code of what I do:

public static void mysql_query(string sServer, string sQuery)
    {
        sQuery = WWW.EscapeURL(sQuery);
        www = new WWW(sServer+"?Query="+sQuery);
        StartCoroutine(WaitForRequest(www));
        if(www.error == null)
        {
            ResultSet = www.text;
        }
        else
        {
            Debug.Log("Error at: "+ www.error);
        }
    }

My problem is that StartCoroutine is obviously a non static method. I can't seem to figure out a work-around to access it in a none static way.

2

Just give it a dummy gameobject to run on. Maybe put a script on that gameobject that gives you singleton-style access to it. You should then be able to do something like `dummyComponent.StartCoroutine( whatever );`

3

If you don’t have at least 1 singleton in your whole project already, get one. And use it like Tetrad already said:

MySingleton.StartCoroutine( MyCoroutine);

Here’s my favorite singleton implementation so far, I adapted from “50 tips for working with Unity” (currently broken link, so here’s the google cache):

using UnityEngine;

/// <summary>
/// Be aware this will not prevent a non singleton constructor
///   such as `T myT = new T();`
/// To prevent that, add `protected T () {}` to your singleton class.
/// </summary>
public class Singleton<T> : MonoBehaviour where T : MonoBehaviour
{
	private static T _instance;
	
	private static object _lock = new object();
	
	public static T Instance
	{
		get
		{
			if (applicationIsQuitting) {
				Debug.LogWarning("[Singleton] Instance "+ typeof(T) +
				" already destroyed on application quit." +
				"Won't create again - returning null.");
				return null;
			}
			
			lock(_lock)
			{
				if (_instance == null)
				{
					_instance = (T) FindObjectOfType(typeof(T));
					
					if (_instance == null)
					{
						GameObject singleton = new GameObject();
						_instance = singleton.AddComponent<T>();
						singleton.name = "(singleton) "+ typeof(T).ToString();
						
						DontDestroyOnLoad(singleton);
						
						Debug.Log("[Singleton] An instance of " + typeof(T) + 
							" is needed in the scene, so '" + singleton +
							"' was created with DontDestroyOnLoad.");
					} else {
						Debug.Log("[Singleton] Using instance already created: " +
							_instance.gameObject.name);
					}
				}
				
				return _instance;
			}
		}
	}
	
	private static bool applicationIsQuitting = false;
	/// <summary>
	/// When unity quits, it destroys objects in a random order.
	/// In principle, a Singleton is only destroyed when application quits.
	/// If any script calls Instance after it have been destroyed, 
	///   it will create a buggy ghost object that will stay on the Editor scene
	///   even after stopping playing the Application. Really bad!
	/// So, this was made to be sure we're not creating that buggy ghost object.
	/// </summary>
	public void OnDestroy () {
		applicationIsQuitting = true;
	}
}
4

If you don’t want a singleton (because your code can become very dependent on them, which makes it difficult to refactor) nor using dummy GameObjects (because you have to create/manage them), you can pass a MonoBehaviour as argument to your static method, and them call StartCoroutine from it.

If you call the static method from a script (Monobehaviour-based object attached to GameObject), you can call the static method using the “this” keyword:

Example static method:

public class Utility
	{
		public static void mysql_query(string sServer, string sQuery, MonoBehaviour justToStartCoroutine)
		{
			sQuery = WWW.EscapeURL(sQuery);
			www = new WWW(sServer + "?Query=" + sQuery);
			justToStartCoroutine.StartCoroutine(WaitForRequest(www));
			if(www.error == null)
			{
				ResultSet = www.text;
			}
			else
			{
				Debug.Log("Error at: " + www.error);
			}
		}
	}

Example call at YourScript.cs:

public class YourScript : MonoBehaviour
	{
// Class members

		void Start()
		{
			Utility.mysql_query("", "", this);
		}
	}