Unity 5 nullreferenceException

Question

Hello fellow programmers all around the world. I have been trying to create an inventory system for a while now and I think I've almost managed it but I get a wee bit of an error(I know that makes no sence in english!). Its a nullreference. here is the code:

using System.Collections;

using System.Collections.Generic; using UnityEngine;

public class Inventory : MonoBehaviour {

private RectTransform inventoryRect;
private float inventoryWidth;
private float inventoryHeight;

public int slots;
public int rows;

public float slotPaddingLeft;
public float slotPaddingTop;
public float slotSize;

public GameObject slotPrefab;

private List<GameObject> allSlots;

private int emptySlot;

// Use this for initialization
void Start () {
    createLayout ();
}

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

}

private void createLayout(){
    allSlots = new List<GameObject> ();

    emptySlot = slots;

    inventoryWidth = (slots / rows) * (slotSize + slotPaddingLeft) + slotPaddingLeft;
    inventoryHeight = rows * (slotSize + slotPaddingTop) + slotPaddingTop;

    inventoryRect = GetComponent<RectTransform> ();
    inventoryRect.SetSizeWithCurrentAnchors (RectTransform.Axis.Horizontal, inventoryWidth);
    inventoryRect.SetSizeWithCurrentAnchors (RectTransform.Axis.Vertical, inventoryHeight);

    int colums = slots / rows;

    for (int y = 0; y < rows; y++) {
        for (int x = 0; x < colums; x++) {
            GameObject newSlot = (GameObject)Instantiate (slotPrefab);

            RectTransform slotRect = newSlot.GetComponent<RectTransform> ();

            newSlot.name = "Slot";
            newSlot.transform.SetParent (this.transform.parent);

            slotRect.localPosition = inventoryRect.localPosition + new Vector3 (slotPaddingLeft * (x + 1) + (slotSize * x), -slotPaddingTop * (y + 1) - (slotSize * y));
            slotRect.SetSizeWithCurrentAnchors (RectTransform.Axis.Horizontal, slotSize);
            slotRect.SetSizeWithCurrentAnchors (RectTransform.Axis.Vertical, slotSize);

            allSlots.Add (newSlot);
        }
    }
}

public bool AddItem(Item item){
    if (item.maxSize == 1) {
        PlaceEmpty (item);
        return true;
    }
    return false;
}

private bool PlaceEmpty(Item item){
    if (emptySlot > 0) {
        foreach (GameObject slot in allSlots) {
            Slot temporary = slot.GetComponent<Slot> ();
            if (temporary.isEmpty) {
                temporary.AddItem (item);
                emptySlot--;
                return true;
            }
        }
    }
    return false;
}

}

The error is temporary but it looks fine to me and referenced(obviously not), so any help?

Any chance that a item in allSlots do not have the Component Slot? allSlots is controlled by you? Any chance that an item is already deleted/destroyed and is null? Could you please copy all your Class code? — Artur Nista, Aug 04 '17 at 19:26
@ArturN it doesn't allow me to enter the whole code says comment is too long? — Христо Петков, Aug 04 '17 at 19:36
@ArturN also I believe the error is in the isEmpty bool property i have set up here is the code for it: ` public bool isEmpty{ get{ return items.Count == 0; } } ` — Христо Петков, Aug 04 '17 at 19:40
So that means `slot` does not have a `Slot` component attached to its GameObject — Matt L., Aug 04 '17 at 19:53
@MattL. okay I get that but I'm still learning so I have no idea how to add it or if it exists to be honest any clues? — Христо Петков, Aug 04 '17 at 19:55
@MattL. sorry to bother you again Sir but I have a different problem now the item shows in the inventory but the problem is that the trigerring doesnt stop and one items fills the whole inventory instead of just one slot. If you could help with this too I will be gratefull. Again sorry to bother you I feel kind of ashamed but as I said I am still learning. Thanks in advance! — Христо Петков, Aug 04 '17 at 20:28

Unity 5 nullreferenceException

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