Issues with C# script interactions

Question

I have been struggling with using methods and variables across different scripts for a while, and have done quite a bit of googling about the various ways it can be done. I have even restarted from scratch a few times.

Is there a certain location relationship you need for these things? Like is there a difference between getting variables and methods from a script on the same object versus in the same parent tree or just in the scene? (And from other scenes, if that is possible)

This code doesn't involve it, but does declaring static or public, exc variables/methods matter when trying to get them from other codes? I have had Unity give me errors about something being static when I didn't have anything static in the whole scene.

Error:

NullReferenceException: Object reference not set to an instance of an object PlayerActions.Update () (at Assets/Content/Scripts/PlayerActions.cs:51)

My Code:

 using UnityEngine;
 using System.Collections;
 
 public class PlayerActions : MonoBehaviour {
     
     OTAnimatingSprite sprite;
     
     // Declares User Input Keys
     bool input_moveLeft;
     bool input_moveRight;
     bool input_jump;
     
     // Use this for initialization
     void Start () {
         sprite = OT.ObjectByName("PlayerAnimations") as OTAnimatingSprite;
         sprite.InitCallBacks(this);
         
         sprite.PlayLoop("idle");
     }
     
     // Update is called once per frame
     void Update () {
         // -------------KEY BINDINGS-------------------
         if ( Input.GetKey("space") )                      // Jump
             input_jump = true;
         else
             input_jump = false;
         
         if ( Input.GetKey("a") || Input.GetKey("left") )  // Move Left
             input_moveLeft = true;
         else
             input_moveLeft = false;
         
         if ( Input.GetKey("d") || Input.GetKey("right") ) // Move Right
             input_moveRight = true;
         else
             input_moveRight = false;
         // -------------KEY BINDINGS-------------------
         
         if ( input_moveLeft ) // -X
         {
                     sprite.PlayLoop("move");
         }
         else if ( input_moveRight ) // +X
         {
                     sprite.PlayLoopBackward("move");
         }
         else
         {
             sprite.PlayLoop("idle");
         }
 
     }
 }

Code I am trying to follow: http://www.wyrmtale.com/orthello/animations (Scroll down to 'C# Source Code')

P.S. It really confuses me for the examples that name things such as GameObject as they don't directly say what I should be filling in with my own variables, or even what my variables should be. (I mean they do, but in a confusing way.)

Answer 1

Best Answer

Answer by hdgam3r · Sep 15, 2012 at 07:02 AM

It´s very simple actually.

If you want to get a variable from a script (Component) on the same object hierarchy, you only have to reference the gameObject component and then make a search for the script:

 gameObject.GetComponent<YourScriptName>().yourPublicVariable;

Notice the lowercase g, this means that we are searching for the component on our current game object.

You can´t reference other scenes objects. If you want to find for a script attached to another GameObject, you have to use the GameObject class and find (via name, tag, etc.)

 GameObject.Find("ObjectName").GetComponent<YourScriptName>().yourPublicVariable;

Note that now we are using a G.

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fafase · Sep 15, 2012 at 07:34 AM 0

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Note also that if this is done regularly, it is to be avoided. You 'd rather create a reference to the object:

  ScriptName reference;

  void Start(){
     reference = GameObject.Find("Object").GetComponent<ScriptName>();
  }
  void Update(){
     reference.theVariable += 10;
  }

The problem is that Find() needs to find the object among all of your hierarchy, if you have two objects, no worries, if you have thousands, your game will freeze until the object is found. The freeze can be unnoticed or 1/2second or even more.

Issues with C# script interactions

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