// InventoryItem.js

// Icon texture for GUI.
var icon:Texture2D;
// Label for GUI.
var iconLabel:string;

// other item data which you may need...

function Activate() {
    // Activation logic for inventory item.
    gameObject.SetActive(true);
}

function Deactivate() {
    // Deactivation logic for inventory item.
    gameObject.SetActive(false);
}


// Inventory.js

import System.Collections.Generic;

// Fixed length array of items, though you may want to use
// the generic `List` class if you wanted varying length.
var items:List.<InventoryItem> = List.<InventoryItem>();

// Represents the active inventory item.
var activeItem:InventoryItem;

// Temporary content instance.
private var _itemButtonContent:GUIContent = new GUIContent();

function OnGUI() {
    var restoreColor : Color = GUI.contentColor;

    GUILayout.BeginArea(new Rect(0, 0, Screen.width, 70));
    GUILayout.BeginHorizontal();

    // Number of item slots in GUI.
    var slotCount:int = 10;

    // Draw buttons for inventory items.
    for (var i = 0; i < slotCount; ++i) {
        // Show empty non-clickable button?
        if (i >= this.items.Count || this.items[i] == null) {
            GUI.enabled = false;
            GUILayout.Button(GUIContent.none);
            GUI.enabled = true;
        }
        else {
            var item : InventoryItem = this.items[i];

            // Show clickable button.
            _itemButtonContent.image = item.icon;
            _itemButtonContent.text = item.iconLabel;

            // Highlight active item.
            GUI.contentColor = (item == this.activeItem)
                ? Color.red
                : restoreColor;

            if (GUILayout.Button(_itemButtonContent))
                this.ActivateItem(item);
        }
    }

    GUILayout.EndHorizontal();
    GUILayout.EndArea();

    GUI.contentColor = restoreColor;
}

function ActivateItem(item:InventoryItem) {
    // Don't bother, this item is already active!
    if (item == this.activeItem)
        return;

    this.DeactivateItem();

    // Active inventory item!
    this.activeItem = item;
    item.Activate();
}

function DeactivateItem() {
    // No item is active, bail!
    if (this.activeItem == null)
        return;

    activeItem.Deactivate();
    this.activeItem = null;
}


// CollectableTorchObject.js

// The associated inventory item.
var item:InventoryItem;

function OnTriggerEnter(other:Collider) {
    // Has player collided with collectable torch object?
    if (other.tag == "Player") {
        // Add item to inventory.
        var inventory:Inventory = GameObject.Find("Inventory").GetComponent.<Inventory>();
        inventory.items.Add(this.item);

        // Automatically activate new inventory item?
        inventory.ActivateItem(this.item);

        // Destroy collectable object!
        Destroy(this.gameObject);
    }
}