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Question by spuller · Jun 24, 2017 at 09:10 PM · c#scripting problemnullreferenceexceptiondictionaryglobal variable

Unable to use global Dictionary in function. "NullReferenceException"

Hi there!

I'm horribly stuck and have yet to find a solution, and appreciate it in advance any assistance the community can give me. Initially, the script used a list to store a class type 'Questions' which I am trying to create a dictionary so that I have a key->value pair. I call the dictionary in the MainController class shown below

 using System.Collections.Generic;
 
 public class MainController : MonoBehaviour
 {
         public Dictionary<int, Questions> GameQuestions;
 
 functions....
 
 }

I then later use the GameQuestions dictionary in the LoadQuestions function as shown below:

 void Start()
     {
         //Invoke the load question coroutine
         if (Mode == DownloadMode.Offline)
             StartCoroutine(LoadQuestions());
         else if (Mode == DownloadMode.Online)
             StartCoroutine(DownlaodXML());
         else
             StartCoroutine(HybridLoader());
     }
 
 private IEnumerator LoadQuestions()
     {
         //Show the splash screen
         SplashScreen.SetActive(true);
 
         //Hide the retry button
         RetrySplashButton.SetActive(false);
 
         //Activate the splash screen loading animation and start playing it
         SplashScreenLoading.gameObject.SetActive(true);
         SplashScreenLoading.Play();
 
         //load the questions from the XML
         TKContainer ic = TKContainer.Load(OfflinePath);
         
         if (AllQuestions.Count > 0)
         {
             AllQuestions.Clear();
         }
 
         general.load();
 }

When I'm trying to call GameQuestions.Count in the LoadQuestions IEnumerator, I receive the following error.

The errror refers that I never create the GameQuestions variable, yet I have and doesn't seem to recognize it. Visual Studios never errors that I haven't created the variable yet, so I wouldn't know why it isn't being found. I at a lost and can't seem to figure it out. It worked perfectly when it was a list, however errors as a dictionary. The only differences between the two generics is that a dictionary isn't serializable, but I wouldn't think at all that would cause this issue. I have made GameQuestions as a local variable and it does work when it is in the function, however I need it to be a global variable as many other functions rely on it. Once again, thank-you for your assistance and I will provide more information if you need it.

Thank-you!

[1]: /storage/temp/96542-maincontroller.txt

1995edf659c487727bc48f87c3e353bd.png (6.6 kB)
maincontroller.txt (80.0 kB)
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avatar image pako · Jun 24, 2017 at 10:56 PM 1
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To clarify: The error doesn't refer to not having created the GameQuestions variable. It refers to the GameQuestions variable being null, since it hasn't yet been assigned anything of type Dictionary<int, Questions>.

If you assign it a new empty Dictionary<int, Questions>as indicated in @$$anonymous$$roq 's answer, it will not be null any more, and you can then start filling it with items.

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Answer by EpsilonQoppa · Jun 24, 2017 at 10:01 PM

You haven't actually created the dictionary object. Try this:

 public Dictionary<int, Questions> GameQuestions = new Dictionary<int, Questions> ();

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avatar image spuller · Jun 25, 2017 at 03:03 AM 0
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Thank-you for the response Enroq, that resolved my issue

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