gather-and-defend/Assets/Scripts/Ally/AllyUpgrade.cs

using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class AllyUpgrade : MonoBehaviour, IPointerClickHandler
{
    [SerializeField]
    private GameObject _upgradeUI;
    [SerializeField]
    private List<UnitUpgrade> _upgradeList = new List<UnitUpgrade>();
    private GameObject _instance = null;

    public void OnPointerClick(PointerEventData eventData)
    {
        if (eventData.button == 0)  //Left click
        {
            if (!_instance)
            {
                GameObject sceneCanvas = GameObject.Find("Canvas");
                if (sceneCanvas != null)
                {
                    Canvas canvas = sceneCanvas.GetComponent<Canvas>();
                    if (canvas == null)
                    {
                        Debug.Log("Canvas introuvable...");
                    }
                    else
                    {
                        _instance = Instantiate(_upgradeUI, Camera.main.WorldToScreenPoint(transform.position), Quaternion.identity, canvas.transform);
                        AssignUpgrades(canvas);
                        DeselectManager.Instance.SetAllyUpgrade(_instance);
                    }
                }
            }
            else
            {
                Destroy(_instance);
                _instance = null;
            }
        }
    }

    private void AssignUpgrades(Canvas canvas)
    {
        // Assign upgrade Prefabs  
        for (int i = 0; i < _instance.transform.childCount - 1; i++)
        {
            if (_upgradeList.Count > i && _upgradeList[i] != null)
            {
                GameObject upgradeEnfant = _instance.transform.Find("Upgrade" + (i + 1)).gameObject;
                if (upgradeEnfant.TryGetComponent<UpgradePlacementButton>(out UpgradePlacementButton button))
                {
                    button.Initialize(_upgradeList[i], gameObject, canvas);
                }
            }
        }
    }

    private void OnDestroy()
    {
        if (_instance != null)
        {
            Destroy(_instance);
            _instance = null;
        }
    }
}