Error instantiate item at enemy dead

Hi guys i already implement my item DB, my item drop when enemy has 0 hp, i start game fine but when enemy die, it drop the item properly but i get this erro message:

NullReferenceException: Object reference not set to an instance of an object
DropItem.UseDropItem () (at Assets/Scripts/DropItem.cs:32)
CharacterManage.GetHit (Int32 playerDamage) (at Assets/Scripts/CharacterManage.cs:28)
Player.impact () (at Assets/Scripts/Player/Player.cs:44)

This is my scripts, can anyone help me plz?

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. [RequireComponent (typeof (DropItem))]
5.  
6. public abstract class CharacterManage : MonoBehaviour
7. {
8.     public string characterName;
9.  
10.     public int maxHealth;
11.  
12.     public int health;
13.    
14.     public int damage;
15.  
16.     public float range;
17.  
18.     //Attack spped is described one attack per second
19.     public float attackSpeed;
20.  
21.     public void GetHit(int playerDamage)
22.     {
23.         health = health - playerDamage;
24.  
25.         if (health < 0)
26.         {
27.             health = 0;
28.             this.GetComponent<DropItem>().UseDropItem();
29.         }
30.     }
31.  
32.     protected abstract void Attack();
33. }
34.  

Code (CSharp):

1. /// <summary>
2. /// Drop item.
3. /// This script use to control a enemy drop item
4. /// </summary>
5.  
6. using UnityEngine;
7. using System.Collections;
8. using System.Collections.Generic;
9.  
10. public class DropItem : MonoBehaviour {
11.     [System.Serializable]
12.     public class Drop{
13.         public int item_id;
14.         public float percentDrop;
15.     }
16.     public GameObject item_Obj_Pref;
17.     public int gold_min, gold_max;
18.     public List<Drop> item_Drop_List = new List<Drop>();
19.  
20.     public float powerImpulse = 1;
21.  
22.  
23.     public void UseDropItem(){
24.      
25.      
26.         for(int i = 0; i < item_Drop_List.Count; i++){
27.             float percentResult = Random.Range(0,100);
28.             if(percentResult < item_Drop_List[i].percentDrop){
29.                 GameObject go = (GameObject)Instantiate(item_Obj_Pref,transform.position+(Vector3.up),Quaternion.identity);
30.                 go.GetComponent<Rigidbody>().AddForce(new Vector3(Random.Range(-1,1)*1.5f*powerImpulse,1*3*powerImpulse,Random.Range(-1,1)*1.5f*powerImpulse),ForceMode.Impulse);
31.                 Item_Obj item_obj = go.GetComponent<Item_Obj>();
32.                 item_obj.item_id = item_Drop_List[i].item_id;
33.                 item_obj.SetItem();
34.                 if(item_obj.gold){
35.                     item_obj.gold_price = Random.Range(gold_min, gold_max);
36.                 }
37.             }
38.         }
39.     }
40.  
41.  
42. }
43.  

 

The component Item_Obj isn't attached to the object, or the drop list is empty. Specifically at line 31. That's returning a null.

Make 100% sure that there's an Item_Obj attached to the gameobject you're instantiating, and that there's at least one object in the drop list.

 

Tell me just one thing its 100% necessary i hv all drop items in Prefabs? So i can instantiate them right? Cuz im get so confused now... So my enemy has script drop item that ask gameobject to instantiate. So i need create a prefab to instantiate and attach the script item_obj to that prefab right? But the item_obj ask for Game object too... Jesus 5am and im going stupid and crazy loool

 

On line 31 you are requesting an Item_Obj script from the object you're instantiating. That could be returning null.

But, if your list of drops is empty, line 32 will request the item_Drop_List with an index of zero. If there are no drops at all, then it will return a null as well.

So check both of those. Make sure that the item_Drop_List contains at least one item, and that the object your are instantiating has an Item_Obj script.