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Question by Sam3million · Mar 21, 2018 at 03:52 PM · c#damagefallhealth

Fall Damage script not working

I'm new to unity and c#. I wrote a fall damage script and everything seems to work fine. It captures the starting y position and ending y position but then it doesn't take away health. As soon as I hit the ground I get the error

"NullReferenceException: Object reference not set to an instance of an object FallDamage.Update () (at Assets/Scripts/FallDamage.cs:60)"

Also in that line I want to do TakeDamage(startYPos - endYPos - damageThreshold); but it says "can't convert from float to int."

Here is my fall damage script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class FallDamage : MonoBehaviour {
 
     public Transform healthBar;
     public float startYPos;
     public float endYPos;
     public float damageThreshold;
     public bool damageMe = false;
     public bool firstCall = true;
     public bool isGrounded = true;
 
     // Use this for initialization
 
     
 
     void OnCollisionEnter(Collision collision)
     {
         isGrounded = true;
     }
 
     void OnCollisionStay(Collision collision)
     {
         isGrounded = true   ;
     }
 
     void OnCollisionExit(Collision collision)
     {
         isGrounded = false;
     }
 
 
     // Update is called once per frame
     void Update () {
         damageThreshold = 1;
         if(GetComponent<Rigidbody>() && isGrounded == false)
         {
             if(gameObject.transform.position.y > startYPos)
             {
                 firstCall = true;
             }
 
             if(firstCall == true)
             {
                 startYPos = gameObject.transform.position.y;
                 firstCall = false;
                 damageMe = true;
             }
         }
         if(GameObject.FindObjectOfType<Rigidbody>() && isGrounded == true)
         {
             endYPos = gameObject.transform.position.y;
             if(startYPos - endYPos > damageThreshold)
             {
                 if (damageMe == true)
                 {
                     healthBar.GetComponent<Health>().TakeDamage(startYPos - endYPos - damageThreshold);
                     damageMe = false;
                     firstCall = true;
                 }
             }
         }
     }
 }
 



And here is my Health script:

 using UnityEngine;
 using UnityEngine.UI;
 using System.Collections;
 
 public class Health : MonoBehaviour
 {
     public const int maxHealth = 100;
     public int currentHealth = maxHealth;
     public Image healthBar;
 
     float CalculateHealth()
     {
         return (float)currentHealth / maxHealth;
     }
 
     public void TakeDamage(int amount)
     {
         currentHealth -= amount;
         healthBar.fillAmount = CalculateHealth();
         if (currentHealth <= 0)
         {
             Destroy(gameObject);
             currentHealth = 0;
             Debug.Log("Dead!");
         }
 
     }
 
 }


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Answer by exzizt · Mar 21, 2018 at 09:10 PM

Cast from float to int: TakeDamage((int)(startYPos - endYPos - damageThreshold)).

This GameObject.FindObjectOfType<Rigidbody>() should be GetComponent<Rigidbody>().

Better yet, cache your Rigidbody to improve performance and not call GetComponent in Update:

 private Rigidbody _rigidbody;
 void Awake() { _rigidbody = GetComponent<Rigidbody>(); }
 // Now use _rigidbody in your code instead of GetComponent.

Ensure that "healthBar" really does have a Health component attached to it.

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