GodotTutorials/Inventory/CSharp/InventoryController.cs

using Godot;

public partial class InventoryController : Control
{
    [Export] public Inventory Inventory;

    public override void _Ready()
    {
        var inventorySlots = GetTree().GetNodesInGroup("inventory_slots_cs");

        for (int i = 0; i < inventorySlots.Count; i++)
        {
            var slot = (InventorySlot)inventorySlots[i];

            slot.InitializeSlot(i, Inventory);
        }
    }
}