Cannot assign transform values to Variables (I guess I'm doing it wrong)

Unity Engine
,
1

So I have some simple code, and now want to assign a new target position to move a sprite too (endxy).

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Thumper : MonoBehaviour
{
    private Transform homexy;
    private Transform endxy;
    [SerializeField] private int speed;
    [SerializeField] float endx;
    [SerializeField] float endy;

    private bool thump = true;

    // Start is called before the first frame update
    void Start ()
    {
        homexy.position = this.transform.position;
        endxy.position = new Vector2 (endx, endy);
// also tried     new Vector3 (endx, endy, 0f); // also didn't work
    }
    void Update ()
    {
    //other code to move Thumper here (removed for clarity)
    }
}

However, The transforms (homexy & endxy) are always null - They do not populate with any values?
Can someone explain how I should set them up, and why the straight assignment doesn’t work please?
Happy to try and work out the right code, when I understand why the above doesn’t work.

Many Thanks (Be kind, first post here) :slight_smile:

2

I don’t see any code above assigning values to either homexy or endxy and they are private non-serializefield, so… null!

The answer is always the same… ALWAYS!

How to fix a NullReferenceException error

https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/

Three steps to success:

  • Identify what is null ← any other action taken before this step is WASTED TIME
  • Identify why it is null
  • Fix that

ALSO: as will ALL Component-derived types you may never new() up one yourself. You must either drag it in or GetComponent() it from another GameObject.

3

Do these lines NOT do that then?
endx and endy DO have values.

  • homexy.position = this.transform.position;
  • endxy.position = new Vector2 (endx, endy);
4

homexy is a Transform, so you’d need to assign a Transform to it (which is a component attached to an object in the scene)

If you just want to store the position, then make them Vector2s

private Vector2 homexy;
private Vector2 endxy;
5

Correct. No more than buying sofas gives you a house to put them in.

Transforms, like any Unity Component, will NEVER exist anywhere except connected to a GameObject, so drag one in there from your scene or prefab or whatever you’re trying to do.

Otherwise if you just need to store a Vector3, then declare that type of field.

This might also help your brain lock around the idea of why that thing is null:

Value Types vs Reference Types:

https://discussions.unity.com/t/826396/4

Vector3s are value types (structs)

Transforms are reference types (classes)

6

Just for clarity, and to close this thread. I have since changed the Transforms to Vector3’s and they do the job perfectly.
I think I understand Kurt’s point about not being able to create a “Transform” from thin air, but alter an existing one instead. I guess I made the “rookie” mistake of thinking that a “Transform” was just the Vector co-ordinates.
Anyhow - Thanks for the responses (especially flashframe), as that pointed me in the right direction, and my code is now working, and I am still learning :slight_smile: