Unity C# - Trying to call a method of an instance of a class defined in a script

Question

I am trying to call a function assigned to a canvas object but I can't figure out what method I should use:

ScoringSystem send;
send.AddPoints();

This method does not work and I get the following error:

NullReferenceException: Object reference not set to an instance of an object
ObHost.Update () (at Assets/Scripts/ObHost.cs:39)

The name of the script I am calling the function from is ObHost. The function is in a script called ScoringSystem. The function is called AddPoints().

I really don't know what to do here because I have tried other methods but they involve a game object, whereas my function is in a canvas.

Answer 1

You did not initialize the instance send of the class ScoringSystem, so a NullReferenceException is raised.

And since send is a null reference, any call to a member or a method will fail with a NullReferenceException.

Declaring an variable for an instance, and initializing it are two different things, that are usually done in a single statement, with a call to a constructor (new) or to a static factory method.

All you have to do is initialize the variable send:

// Put any required or optional parameter in the constructor call
ScoringSystem send = new ScoringSystem();

There are some examples here with condition to the object variables: https://www.geeksforgeeks.org/object-and-collection-initializer-in-c-sharp/#:~:text=In%20object%20initializer%2C%20you%20can,the%20variable%20in%20the%20assignment.