Moving object

Unity Engine
1

My code:

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

public class Cube : MonoBehaviour {

private Rigidbody rigidbody;
// Use this for initialization
void Start ()
{

}

// Update is called once per frame
void Update ()
{
if (Input.GetKey (KeyCode.UpArrow))
{
rigidbody.AddForce (Vector2.up * 2000);
}
}
}

Problem in 7th line (private Rigidbody rigidbody;):

“no value will ever be assigned to the “Cube.Rigidbody” field and the default value of this field will always be used: null.”

I dont know what should I do, cube does not move when I pressing up arrow, can someone help me?

2

As the error is trying to say, you need to initialize your variable. If you’re confused about this in the future go look at the example in the manual: Unity - Scripting API: Rigidbody.AddForce

void Start ()
{
  rigidbody = GetComponent<Rigidbody>();
}

Additionally, applying forces to a rigidbody in Update is a bad idea. You want to capture the input in Update but apply the force in FixedUpdate.

3

thank you now this works, but I have one problem. my cube is rolling and changing rotation and I dont know what should I do, I tried to do this with sphere, but this is rolling too.

4

A good place to start would be to describe exactly what behavior you are trying to accomplish.