1

Trying to use WWW to pull data from my webservice and I originally got an error saying “WWW is not ready downloading yet”.

So, I figure I have to use “yield return www;”, which led to me to using a delegate method. Now I am getting error: “NullReferenceException
UnityEngine.MonoBehaviour.StartCoroutine (IEnumerator routine)”.

I’m an experience .net C# developer, but this is seriously giving me trouble. What is the best way to go about something like this? Thanks!

In my ItemCatelog class:

private void RequestItemCatelog()
{
	data.GetItemCatelog(RecieveItemCatelog);
}

private void RecieveItemCatelog(CatelogItem[] items)
{
	Debug.Log(items[0].ItemName);
}

and in my datahelper class:

	public delegate void GetItemCatelogReceiver(CatelogItem[] items);
	public void GetItemCatelog(GetItemCatelogReceiver _GetItemCatelogReceiver)
	{
		StartCoroutine(GetItemCatelogResponse(_GetItemCatelogReceiver));
	}
	
	IEnumerator GetItemCatelogResponse(GetItemCatelogReceiver _GetItemCatelogReceiver)
	{
		WWW www = new WWW(url);
		Debug.Log(www.text);
		yield return www;	
		
		CatelogItem[] items = JsonMapper.ToObject<CatelogItem[]>(www.text);
		Debug.Log(www.text);
		_GetItemCatelogReceiver(items);
	}
5

I got it working!

void Awake()
    {
        isFirstRound = true;

        WWW result = GET("http://dev.wisc-online.com/Prototypes/muscle_structure.json");
} 


public WWW GET(string url)
    {
        WWW www = new WWW(url);

        StartCoroutine(WaitForWWW(www));
        //do nothing untill json is loaded 
        while (!www.isDone) {  }

        if (www.error == null || www.error == "")
        {
            gameData = convertFromJSONToMyClass(www.text);
            Debug.Log("gameData = " + gameData);
        }
        else
        {
            Debug.Log("WWW error: " + www.error);
        }

        return www;
    }
    IEnumerator WaitForWWW(WWW www)
    {
        yield return www;
    }
2

I had a problem when i copied your script because of requesting www.text before yielding to www. Here is the test I did with success and excluding the json list.

using UnityEngine;
using System.Collections;

public class WWWTest : MonoBehaviour 
{
	public delegate void GetItemCatelogReceiver(string text);
	void Start()
	{
		 GetItemCatelog(RecieveItemCatelog);
	}
	
	void GetItemCatelog(GetItemCatelogReceiver _GetItemCatelogReceiver)
    {
       StartCoroutine("GetItemCatelogResponse", _GetItemCatelogReceiver);
    }
 
    IEnumerator GetItemCatelogResponse(GetItemCatelogReceiver _GetItemCatelogReceiver)
    {
       WWW www = new WWW("http://www.google.com");
       yield return www; 
 
       _GetItemCatelogReceiver(www.text);
    }
	
	private void RecieveItemCatelog(string text)
	{
	    Debug.Log(text);
	}

}
3

The problem was my ItemCatelog class was instantiating the DataHelper class with new(). Old .net habits die hard.

“yield return www” I had put in place to reproduce the “WWW is not ready downloading yet” error and accidently made it into the snippet.

4

In my case, my game must wait for the web results before continuing, there is nothing to do while the results arrive, so I programmed it to wait until WWW is ready downloading.

using UnityEngine;
using System.Collections;

public class Principal : MonoBehaviour
{
	// This could be one of many methods which require data from web.
	public void Browse () 
	{
		// Make a call to the "GET" method providing the url.
		WWW result = GET("https://www.google.com.mx/search?q=UnityException%3A+WWW+is+not+ready+downloading+yet&oq=UnityException%3A+WWW+is+not+ready+downloading+yet&aqs=chrome..69i57j69i58.349j0j9&sourceid=chrome&es_sm=93&ie=UTF-8#safe=off&q=UnityException:+WWW+is+not+ready+downloading+yet");

		// Show the output.
		Debug.Log(result.text);
	}

	// The "GET" method is apart because it could be called from many methods.
	public WWW GET (string url)
	{
		// Create the WWW object and provide the url of this web request.
		WWW www = new WWW (url);

		// Run the web call in the background.
		StartCoroutine (WaitForRequest (www));

		// Do nothing until the response is complete.
		while (!www.isDone) {}

		// Deliver the result to the method that called this one.
		return www;
	}

	// Run the web call and deliver the result as it is arriving.
	private IEnumerator WaitForRequest (WWW www)
	{
		yield return www;
	}
}