Use of unassigned local variable "prevPos"?

Unity Engine
1

This code is supposed to be code for picking up objects, but it just gives me this error on line 29: Use of unassigned local variable ‘prevPos’

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

public class Pickup_cube : MonoBehaviour {

    //this decides when you are holding the cube
    public bool holding;
    public Rigidbody rb;


    void OnMouseDown()
    {
        holding = true;
    }

    void OnMouseUp()
    {
        holding = false;
    }

    void Update()
    //this decides what the cube will do when you are holding it
    {
        Vector3 prevPos;//cached position

        //calculating and applying the force
        Vector3 dist = transform.position - prevPos;
        float time = Time.deltaTime;
        rb.AddForce((dist/(time * time)) *rb.mass);

        //caching position
        prevPos = transform.position;
        if (Input.GetButtonDown ("Fire2")) {
               
        }
        if (Input.GetButtonUp ("Fire2")) {
           
        }
        if(holding == true)
        {
            this.transform.SetParent(Camera.main.transform);
            Rigidbody Rigidbody = gameObject.GetComponentInParent<Rigidbody>( );
            Rigidbody.useGravity = false;
            Rigidbody.drag = 100;
            Rigidbody.isKinematic = false;
        }
        if(holding == false)
        {
            this.transform.parent = null;
            Rigidbody Rigidbody = gameObject.GetComponentInParent<Rigidbody>( );
            Rigidbody.useGravity = true;
            Rigidbody.drag = 0;
            Rigidbody.isKinematic = false;
        }
    }
}
2

You need to initialized prevPos.

Change:

Vector3 prevPos;

to:

Vector3 prevPos = new Vector3(0, 0, 0);
3

Thank you so much!

4

That will make the error go away. But the code probably won’t function as desired.

It looks like the intent is to have previousPos as a class variable. So move the declaration on line 25 up to line 10.

5

What do you mean “cached position”? Is this something that needs to be persisted from the previous frame? Then declare it at the class level.