Programming a Shrinking Cube in Unity. No Errors but no Visible Changes

Question

So I'm new to unity and trying to create a cube programmatically at the start, and when you press the down arrow key it decrements gradually.

using System.Collections.Generic;
using UnityEngine;

public class LetThereBeLight : MonoBehaviour
{
    public GameObject rubixCube;
    public Vector3 newScale;
    public Vector3 currentScale;`

    void Start()
    {
        GameObject rubixCube = GameObject.CreatePrimitive(PrimitiveType.Cube);
        rubixCube.transform.localScale = new Vector3(10f, 10f, 10f);
        rubixCube.transform.position = new Vector3(0, 0, 0);

        currentScale = rubixCube.transform.localScale;
        newScale = new Vector3(-1f, -1f, -1f);
    }

    void Update()
    {
        if (Input.GetKey(KeyCode.DownArrow)){

            currentScale += newScale;

            if(currentScale.x < 10){
                print("Well at least this worked");
            }
        }
    }
}

When I run the play button in unity, the cube is created and I receive no errors but the cube does not shrink when I press the down arrow key. However, I know that the size of the vector is decrementing because I tell it to print a message as a test and it does so. But there are no visible changes to the size of the cube in the viewer.

Also, I originally put

currentScale = rubixCube.transform.localScale; in the void Update() function rather than the void Start() and it gave me an error Unassigned reference exception: The variable rubixCube of LetThereBeLight has not been assigned but shouldn't it not matter what function it is in whether it is called upon start or looped over because I already made rubixCube a public GameObject outside of both functions?

Does anyone know how to solve this? Why doesn't this script work?

Does this answer your question? [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — BugFinder, Mar 01 '22 at 01:20
You declare your cube locally. Therefore there is no reference elsewhere — BugFinder, Mar 01 '22 at 01:20

score 0 · Answer 1 · edited Mar 01 '22 at 08:03

Two issues:

In the Start you do
```
GameObject rubixCube = GameObject.CreatePrimitive(PrimitiveType.Cube);
```
which creates a local variable and hides the class field with equal name rubixCube!

=> The class field rubixCube you later try to use in Update is never assigned!

In Start it should rather simply be
```
rubixCube = GameObject.CreatePrimitive(PrimitiveType.Cube);
```
Then in Update you do
```
 currentScale += newScale;
```
You are changing the field currentScale, which is a Vector3 value ... but that is all.

You are not actually changing the Transform component on the GameObject itself at all, so the cube in your game is not actually being affected at all by this code.

You rather have to actually assign something back to the property
```
currentScale += newScale;
rubixCube.transform.localScale = currentScale;
```

I edited your answer a bit to make it complete. Also note that for this it doesn't really matter at all that `Vector3` is a struct or class .. what matters is that `Transform.localScale` is a **property** and unless you assign something to it, it's setter is never called which then handles the actual assignment in the underlying c++ layer — derHugo, Mar 01 '22 at 08:05

score 0 · Answer 2 · edited Mar 02 '22 at 02:59

0

I tried to modify your code, I searched for information, and clicked the "CreaterubixCube" button in the OnGUI() function to call the "CreatePrimitive" method, thereby creating a rubixCub object and adding its position attribute. I also just learned unity3d.

edited Mar 02 '22 at 02:59

Dharman

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answered Mar 02 '22 at 02:53

Housheng-MSFT

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Programming a Shrinking Cube in Unity. No Errors but no Visible Changes

2 Answers2