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Question by smithr3339 · Oct 20, 2013 at 09:55 PM · errorvariablevalue

Getting error: Cannot modify a value type return value of `UnityEngine.Rigidbody.velocity'. Consider storing the value in a temporary variable

I made a program using javascript, but I am curently learning C# so I wanted to transfer it over. I think I fixed most of the problems but this one: Cannot modify a value type return value of `UnityEngine.Rigidbody.velocity'. Consider storing the value in a temporary variable

     using UnityEngine;
     using System.Collections;
         
     public class MYCLASSNAME : MonoBehaviour
     {
         
         int rotationSpeed= 100;
         int jumpHeight= 8;
         
         bool isFalling = false;
         
         void  Update ()
         {
             //Left to Right, A and D
             float rotation = Input.GetAxis ("Horizontal") * rotationSpeed;
             rotation *= Time.deltaTime;
             rigidbody.AddRelativeTorque(Vector3.back * rotation);
         
             if (Input.GetKeyDown (KeyCode.Space) && isFalling == false)
             {
                 rigidbody.velocity.y = jumpHeight;
             }
             isFalling = true;
         }
         void OnCollisionStay ()
         {
             isFalling = false;
         }
         
     }
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avatar image tw1st3d · Oct 20, 2013 at 09:55 PM 1
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use the 101/010 button to format your code, so we don't have to try and figure it out.

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Answer by rutter · Oct 20, 2013 at 10:03 PM

This:

 rigidbody.velocity.y = jumpHeight;

Could be:

 Vector3 v = rigidbody.velocity;
 v.y = jumpHeight;
 rigidbody.velocity = v;

You could name it whatever you want, but that's pretty much the temp variable pattern they're suggesting.

As an alternative, you can use AddForce() to accomplish roughly the same thing:

 rigidbody.AddForce(Vector3.up * jumpHeight, ForceMode.VelocityChange);
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avatar image Domain · Nov 27, 2013 at 03:31 AM 0
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this makes the object fly into the sky and never fall back down...?

avatar image Domain · Nov 27, 2013 at 03:41 AM 0
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oh, the variable I was using was a float, I don't know why but that made it totally flip out. Oh well. This was good, thanks.

avatar image cmartin97 · Mar 06, 2014 at 12:29 AM 0
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Very helpful, thanks!

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