How to make GUI Rect child of an object?

Question

I have this problem, that I draw a new Rect with a GUI: it only draws now on screen. What I want to do is to make this drawing a child of an object, so I can hide this with SetActive(false) . This will be only available when players will pause and open Inventory. The game is 2D for Android.

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

public class Inventory : MonoBehaviour
{
    public int SlotsX, SlotsY;

    public GUISkin Skin;

    public List<Item> inventory = new List<Item>();
    public List<Item> slots = new List<Item>();

    private ItemDatabase database;

    void Start()
    {
        for (int i = 0; i < (SlotsX * SlotsY); i++)
        {
            slots.Add(new Item());
        }

        database = GameObject.FindGameObjectWithTag("Item Database").GetComponent<ItemDatabase>();
        inventory.Add(database.Items[0]);
        inventory.Add(database.Items[1]);
        inventory.Add(database.Items[3]);
        inventory.Add(database.Items[4]);
        inventory.Add(database.Items[5]);
        inventory.Add(database.Items[6]);
    }

    void OnGUI()
    {
        GUI.skin = Skin;
        DrawInventory();
        for (int i = 0; i < inventory.Count; i++)
        {
            GUI.Label(new Rect(10, i * 40, 200, 50), inventory[i].itemName);
        }
    }

    void DrawInventory()
    {
        for (int x = 0; x < SlotsX; x++)
        {
            for (int y = 0; y < SlotsY; y++)
            {
                GUI.Box(new Rect(x * 180, y * 180, 160, 160), "", Skin.GetStyle("Slot"));
            }
        }
    }
}

Answer 1

To set the parent of a GameObject in Unity programmatically , simply use this: childGameObject.transform.SetParent(parentGameObject);

EDIT: Turns out it isn't this simple with OnGUI. Follow Draco18s's advice and use the new GUI system.