Unity Error: UnityEngine.Component' does not contain a definition for `velocity'

Question

I am very new to C#, so forgive me if this is obvious.

I am following the steps in this tutorial and have run into a problem on step six. The error it gives is this: The error it gives is this:

UnityEngine.Component' does not contain a definition for `velocity' and no extension method `velocity' of type `UnityEngine.Component' could be found. Are you missing an assembly reference?'

Here is the code:

using UnityEngine;
using System.Collections;

public class RobotController : MonoBehaviour {
//This will be our maximum speed as we will always be multiplying by 1
public float maxSpeed = 2f;
//a boolean value to represent whether we are facing left or not
bool facingLeft = true;
//a value to represent our Animator
Animator anim;
// Use this for initialization
void Start () {
  //set anim to our animator
  anim = GetComponent<Animator>();

}

// Update is called once per frame
void FixedUpdate () {

  float move = Input.GetAxis ("Horizontal");//Gives us of one if we are moving via the arrow keys
  //move our Players rigidbody
  rigidbody2D.velocity = new Vector3 (move * maxSpeed, rigidbody2D.velocity.y);
  //set our speed
  anim.SetFloat ("Speed",Mathf.Abs (move));
  //if we are moving left but not facing left flip, and vice versa
  if (move < 0 && !facingLeft) {

   Flip ();
  } else if (move > 0 && facingLeft) {
   Flip ();
  }
}

//flip if needed
void Flip(){
  facingLeft = !facingLeft;
  Vector3 theScale = transform.localScale;
  theScale.x *= -1;
  transform.localScale = theScale;
}
}

The error is on line 23:

rigidbody2D.velocity = new Vector3 (move * maxSpeed, rigidbody2D.velocity.y);

Answer 1

rigidbody2D used to be a variable inherited from Component which MonoBehaviour is inherits. It is now deprecated.

Now, you have to declare it and initialize it with GetComponent<Rigidbody>(); just like you did for the Animator(anim) variable in the Start() function. Also, to not confuse yourself with the old variable, I suggest that you rename rigidbody2D to something else. In the example code below, I will rename it to rigid2D and declare it.

If you don't rename it, you might get a warning that says:

Severity Code Description Project File Line Suppression State Warning CS0108 'RobotController.rigidbody2D' hides inherited member 'Component.rigidbody2D'. Use the new keyword if hiding was intended.

public class RobotController: MonoBehaviour
{
    public float maxSpeed = 2f;
    //a boolean value to represent whether we are facing left or not
    bool facingLeft = true;
    //a value to represent our Animator
    Animator anim;

    //Declare rigid2D
    Rigidbody rigid2D;
    // Use this for initialization
    void Start()
    {
        //set anim to our animator
        anim = GetComponent<Animator>();

        //Initialize rigid2D
        rigid2D = GetComponent<Rigidbody>();
    }

    // Update is called once per frame
    void FixedUpdate()
    {

        float move = Input.GetAxis("Horizontal");//Gives us of one if we are moving via the arrow keys
                                                 //move our Players rigidbody
        rigid2D.velocity = new Vector3(move * maxSpeed, rigid2D.velocity.y);
        //set our speed
        anim.SetFloat("Speed", Mathf.Abs(move));
        //if we are moving left but not facing left flip, and vice versa
        if (move < 0 && !facingLeft)
        {

            Flip();
        }
        else if (move > 0 && facingLeft)
        {
            Flip();
        }
    }

    //flip if needed
    void Flip()
    {
        facingLeft = !facingLeft;
        Vector3 theScale = transform.localScale;
        theScale.x *= -1;
        transform.localScale = theScale;
    }
}