harvestdale-unity/Assets/Scripts/UI/InventoryUI.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class InventoryUI : GuiPanel
{
  [SerializeField] private GameObject slotPrefab;
  [SerializeField] private GameObject slotListObj;
  [SerializeField] private List<SlotUI> slotUIList;

  private Inventory playerInventory;

  private void Start()
  {
    Inventory.OnPlayerInventoryChanged += UpdateSlots;
  }
  public override void OnOpen()
  {
    if (slotUIList.Count == 0)
    {
      playerInventory = GameObject.FindGameObjectWithTag("Player").GetComponent<Inventory>();
      CreateSlots();
    }
    UpdateSlots();
    GuiManager.Instance.ClosePanel("Hotbar");
  }

  public override void OnClose()
  {
    GuiManager.Instance.OpenPanel("Hotbar");
  }
  private void CreateSlots()
  {
    playerInventory = GameObject.FindGameObjectWithTag("Player").GetComponent<Inventory>();

    for (int i = 0; i < playerInventory.maxSlots; i++)
    {
      SlotUI newSlot = Instantiate(slotPrefab, Vector3.zero, Quaternion.identity, slotListObj.transform).GetComponent<SlotUI>();
      newSlot.slotIndex = i;
      slotUIList.Add(newSlot);
    }
  }
  private void UpdateSlots()
  {
    int i = 0;
    foreach (SlotUI slotUi in slotUIList)
    {
      slotUi.SetInventoryItem(playerInventory.items[i]);
      i++;
    }
  }

}