NullReferenceException that shouldn't exist!

I am making a multiplayer fps game loosely based off of brackey's tutorial. I cannot show all the scripts because I don't want people copying my code...

I get a reference exception whenever I open the game-selection scene. Here is the error:

NullReferenceException: Object reference...... blablabla

I look at the script: (just posting that section)

Code (CSharp):

1. IEnumerator sendGetDataRequest(string username, string password, OnDataReceivedCallback onDataReceived)
2.     {
3.         string data = "ERROR";
4.  
5.         IEnumerator eeee = DCF.GetUserData(username, password);
6.         while (eeee.MoveNext())
7.         {
8.             yield return eeee.Current;
9.         }
10.         WWW returnedddd = eeee.Current as WWW;
11.         if (returnedddd.text != "Error") // ERROR HERE!!!
12.         {
13.             if (returnedddd.text == "ContainsUnsupportedSymbol")
14.             {
15.                 //One of the parameters contained a - symbol
16.                 Debug.Log("Get Data Error: Contains Unsupported Symbol '-'");
17.             }
18.             else
19.             {
20.                 //Data received in returned.text variable
21.                 string DataRecieved = returnedddd.text;
22.                 data = DataRecieved;
23.             }
24.         }
25.         else
26.         {
27.             //Error occurred. For more information of the error, DC.Login could
28.             //be used with the same username and password
29.             Debug.Log("Data Download Error. Try again in a few minutes. If problem still occurs, contact us on DISCORD.");
30.         }
31.  
32.         if (onDataReceived != null)
33.             onDataReceived.Invoke(data);
34.     }
35.  
36. }

the error is on line 108 (if (returnedddd.text != "Error"))

But that is an if statement, and the object it defines is instantiated right above that if statment. Do what you can with what I gave you... Thanks..

 

Line 108 is line 11 here...

 

Then right before your if statement you should do debug.log to print out what returnedddd.text is to see if it is returning null. Also can't hurt to print out what returnedddd value is as well. Just because you created it doesn't mean it doesn't have a null value.

 

Sure the WWW variable is declared right above it. But you have it set to the IEnumerator.Current value that you just finished looping in the 'while' loop before that.

When an enumerator finishes its last 'MoveNext' and returns false, it also sets its Current property to null. You're not getting anything out of it. (or at least that's the default behaviour for most enumerators, including iterator functions... but since IEnumerator is an interface it technically depends on the implementor and how it behaves)

Now from looking at your logic, I presume your enumerator that you're while looping should return a WWW as its last member. Set that to some variable during the while loop. Also, since there is no guarantee that this is so (since DCF.GetUserData is just returning an IEnumerator)... you should probably also test to make sure that it was a WWW. Unless that is DCF.GetUserData can guarantee this, in which case it probably should be defined as such as part of its shape/interface... but alas, I do not know your implementation of DCF.GetUserData since:

I assure you, we're not all here to steal your code.

 

Or people could come here and tell you how to make it better... but it's up to you.

 

thanks guys I will try it!

 

Mind if I put your usernames in the credits under special thanks. Since technically, you just helped with development?

 

heres the whole script lordofduct

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3. using DatabaseControl;
4. using UnityEngine.SceneManagement;
5.  
6. public class UserAccountManager : MonoBehaviour
7. {
8.  
9.     public static UserAccountManager instance;
10.  
11.     void Awake()
12.     {
13.         if (instance != null)
14.         {
15.             Destroy(gameObject);
16.             return;
17.         }
18.  
19.         instance = this;
20.         DontDestroyOnLoad(this);
21.     }
22.  
23.     public static string LoggedIn_Username { get; protected set; } //stores username once logged in
24.     private static string LoggedIn_Password = ""; //stores password once logged in
25.  
26.     public static bool IsLoggedIn { get; protected set; }
27.  
28.     public string loggedInSceneName = "Lobby";
29.     public string loggedOutSceneName = "LoginMenu";
30.  
31.     public delegate void OnDataReceivedCallback(string data);
32.  
33.     public void LogOut()
34.     {
35.         LoggedIn_Username = "";
36.         LoggedIn_Password = "";
37.  
38.         IsLoggedIn = false;
39.  
40.         Debug.Log("Logged out!");
41.  
42.         SceneManager.LoadScene(loggedOutSceneName);
43.     }
44.  
45.     public void LogIn(string username, string password)
46.     {
47.         LoggedIn_Username = username;
48.         LoggedIn_Password = password;
49.  
50.         IsLoggedIn = true;
51.  
52.         Debug.Log("Logging in as " + username);
53.  
54.         SceneManager.LoadScene(loggedInSceneName);
55.     }
56.  
57.     public void SendData(string data)
58.     { //called when the 'Send Data' button on the data part is pressed
59.         if (IsLoggedIn)
60.         {
61.             //ready to send request
62.             StartCoroutine(sendSendDataRequest(LoggedIn_Username, LoggedIn_Password, data)); //calls function to send: send data request
63.         }
64.     }
65.  
66.     IEnumerator sendSendDataRequest(string username, string password, string data)
67.     {
68.         IEnumerator eee = DCF.SetUserData(username, password, data);
69.         while (eee.MoveNext())
70.         {
71.             yield return eee.Current;
72.         }
73.         WWW returneddd = eee.Current as WWW;
74.         Debug.Log("Okay at 74 (DEBUGGING)");
75.         if (returneddd.text == "ContainsUnsupportedSymbol")
76.         {
77.             //One of the parameters contained a - symbol
78.             Debug.Log("Data Upload Error: Could be a server error. Try again in a few minutes. If problem still occurs, contact us on DISCORD.");
79.         }
80.         if (returneddd.text == "Error")
81.         {
82.             //Error occurred. For more information of the error, DC.Login could
83.             //be used with the same username and password
84.             Debug.Log("Data Upload Error: Contains Unsupported Symbol '-'");
85.         }          
86.     }
87.  
88.     public void GetData(OnDataReceivedCallback onDataReceived)
89.     { //called when the 'Get Data' button on the data part is pressed
90.  
91.         if (IsLoggedIn)
92.         {
93.             //ready to send request
94.             StartCoroutine(sendGetDataRequest(LoggedIn_Username, LoggedIn_Password, onDataReceived)); //calls function to send get data request
95.         }
96.     }
97.  
98.     IEnumerator sendGetDataRequest(string username, string password, OnDataReceivedCallback onDataReceived)
99.     {
100.         string data = "ERROR";
101.  
102.         IEnumerator eeee = DCF.GetUserData(username, password);
103.         while (eeee.MoveNext())
104.         {
105.             yield return eeee.Current;
106.         }
107.         WWW returnedddd = eeee.Current as WWW;
108.         Debug.Log("")
109.         if (returnedddd.text != "Error")
110.         {
111.             if (returnedddd.text == "ContainsUnsupportedSymbol")
112.             {
113.                 //One of the parameters contained a - symbol
114.                 Debug.Log("Get Data Error: Contains Unsupported Symbol '-'");
115.             }
116.             else
117.             {
118.                 //Data received in returned.text variable
119.                 string DataRecieved = returnedddd.text;
120.                 data = DataRecieved;
121.             }
122.         }
123.         else
124.         {
125.             //Error occurred. For more information of the error, DC.Login could
126.             //be used with the same username and password
127.             Debug.Log("Data Download Error. Try again in a few minutes. If problem still occurs, contact us on DISCORD.");
128.         }
129.  
130.         if (onDataReceived != null)
131.             onDataReceived.Invoke(data);
132.     }
133.  
134. }

 

 do debug.log to print out what returnedddd.text is to see if it is returning null.

Result: Returns Null

what exactly am I supposed to change now.

 

Not necessary... this sort of assistance is what forums are for.

They were suggesting you use a Debug.Log to see what returneddd.text spat out. They thought maybe the text was coming back null.

Thing is, this is inconsequential. Comparing a null string to "Error!" doesn't throw an exception. You're not directly accessing members of 'text', so it doesn't matter if it were null.

And that's because, as was pointed out, your null object was the 'returneddd' in and of itself.

How you'd really deal with it is something along the lines of:

Code (csharp):

1.  
2.     IEnumerator sendGetDataRequest(string username, string password, OnDataReceivedCallback onDataReceived)
3.     {
4.         string data = "ERROR";
5.  
6.         IEnumerator eeee = DCF.GetUserData(username, password);
7.         WWW returnedddd = null;
8.         while (eeee.MoveNext())
9.         {
10.             returnedddd = eeee.Current as WWW;
11.             yield return eeee.Current;
12.         }
13.      
14.         if (returnedddd != null && returnedddd.text != "Error") // ERROR HERE!!!
15.         {
16.  

Though personally I find this to be code smell, and that code smell is creeping out of the DCF.GetUserData method. Personally I'd be refactoring that method so that you could cleanly access the WWW object from it.

...

On a tangent... what is up with the 'eeee' and 'dddd' and what not in your variable names? I've seen some weird naming conventions over the many years I've been coding... and that one is a first for me.

 

You've been awesome lordofduct... Thanks...