Game Foundation Tutorials

Playing with items at runtime

We've created an inventory item definition in the previous tutorial. Let's see what we can do with it.

Initialization of Game Foundation at runtime

  • Create a new scene
  • Create a new game object and name it Game Foundation Init (the name doesn't really matter).
  • Add a new MonoBehaviour to your project and name it GFInit.
  • Copy the following code into this script file:
using System;
using UnityEngine;
using UnityEngine.GameFoundation;
using UnityEngine.GameFoundation.DataAccessLayers;

public class GFInit : MonoBehaviour
{
    void Start()
    {
        // Creates a new data layer for Game Foundation,
        // with the default parameters.
        var dataLayer = new MemoryDataLayer();

        // Initializes Game Foundation with the data layer.
        GameFoundation.Initialize
            (dataLayer, OnInitSucceeded, OnInitFailed);
    }

    // Called when Game Foundation is successfully
    // initialized.
    void OnInitSucceeded()
    {
        Debug.Log("Game Foundation is successfully initialized");
    }

    // Called if Game Foundation initialization fails 
    void OnInitFailed(Exception error)
    {
        Debug.LogException(error);
    }
}

Come back to your editor, and start your game by pushing the Play button. In the console, you should see two log entries:

! `Successfully initialized Game Foundation version x.y.z`
! `Game Foundation is successfully initialized`

The second is the one you've written, while the first is logged by Game Foundation automatically.

The Data Layer

Game Foundation is the general API to manipulate your items, but it needs a source to load the data, and a destination to push the states of its items.

The data layer fulfills this role. It gives Game Foundation a catalog of the static data, and Game Foundation notifies it of all the instance data it creates, modifies, or destroys.

The default constructor of the MemoryDataLayer loads the database of the static data you've manipulated in the previous tutorial. You can find this database in the Assets/GameFoundation folder, with the name GameFoundationDatabase.asset.

Getting the inventory item definition at runtime

Go back to the OnInitSucceeded method, and add the following code, right under the Debug.Log statement:

void OnInitSucceeded()
{
    Debug.Log("Game Foundation is successfully initialized");

    // Use the ID you've used in the previous tutorial.
    const string definitionId = "myFirstItem";

    // The inventory item definitions are available in the
    // inventoryCatalog of the database.
    var catalog = GameFoundation.catalogs.inventoryCatalog;

    // Finding a definition takes a non-null string parameter,
    // but it can fail to find the definition.
    var definition = catalog.FindItem(definitionId);

    if (definition is null)
    {
        Debug.Log($"Definition {definitionId} not found");
        return;
    }

    // You should be able to get information from your
    // definition now.
    Debug.Log($"Definition {definition.id} '{definition.displayName}' found.");
}

Compile and start your scene. You should see the following log in your console:

! Definition myFirstItem 'My First Item' found.

The catalogs

The static data of Game Foundation can be found in the database property of Game Foundation. The data is organized among different catalogs:

Creating an item instance

Now that we have an inventory item definition, we can create an item instance. Go back to your OnInitSucceeded method, then append the following lines:

var item = InventoryManager.CreateItem(definition);

Debug.Log($"Item {item.id} of definition '{item.definition.id}' created");

Compile and start your scene. You should see a new log entry:

Item xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx of definition 'myFirstItem' created

When created, an item instance is assigned a unique id, as a string version of a GUID. This ID ensure that the item will remain unique.

Removing the item instance

Now that we have an item instance, why not trying to remove it. Go back to your OnInitSucceeded method, then append the following lines:

var removed = InventoryManager.RemoveItem(item);

if (!removed)
{
    Debug.LogError($"Unable to remove item {item.id}");
    return;
}

Debug.Log($"Item {item.id} successfully removed. Its discarded value is {item.discarded}");

Compile and start your scene. You should see a new log entry:

Item 52adebc3-cee6-4706-b0f9-847a8c10a512 successfully removed. Its discarded value is True

Removing an item from Game Foundation doesn't destroy the object. It is a managed object, so it cannot be really removed as long as it is not garbage collected. It just tells the data layer that the item has to be removed from the persistence, and it sets the item.discarded property to true.
A lot of properties are still accessible, but you cannot modify your object anymore, nor use it in the other APIs of Game Foundation. This is pretty convenient, as you'd need to keep an access to the properties of a removed item in case you need to propagate its removal in your gameplay code.

Conclusion

Item instance can represent a lot of different aspects of your game. As soon as you want to manipulate an object with static data and properties, being able to create it, but also destroying on demand, and if you want to persist it in the player profile, then item instance should be the feature you'd need.

It can be the player inventory: the character equipment, consumable items like potions or buffs. It can be the character itself.
The way you'll use Inventory Item Definition and their instance is up to you.

But what if what you want now, is to play with currencies? Let's switch to the next tutorial then.

Final code source of this tutorial

using System;
using UnityEngine;
using UnityEngine.GameFoundation;
using UnityEngine.GameFoundation.DataAccessLayers;

public class GFInit : MonoBehaviour
{
    void Start()
    {
        // Creates a new data layer for Game Foundation,
        // with the default parameters.
        var dataLayer = new MemoryDataLayer();

        // Initializes Game Foundation with the data layer.
        GameFoundation.Initialize
            (dataLayer, OnInitSucceeded, OnInitFailed);
    }

    // Called when Game Foundation is successfully
    // initialized.
    void OnInitSucceeded()
    {
        Debug.Log("Game Foundation is successfully initialized");

        // Use the ID you've used in the previous tutorial.
        const string definitionId = "myFirstItem";

        // The inventory item definitions are available in the
        // inventoryCatalog of the database.
        var catalog = GameFoundation.catalogs.inventoryCatalog;

        // Finding a definition takes a non-null string parameter,
        // but it can fail to find the definition.
        var definition = catalog.FindItem(definitionId);

        if (definition is null)
        {
            Debug.Log($"Definition {definitionId} not found");
            return;
        }

        // You should be able to get information from your
        // definition now.
        Debug.Log($"Definition {definition.id} '{definition.displayName}' found.");

        var item = InventoryManager.CreateItem(definition);

        Debug.Log($"Item {item.id} of definition '{item.definition.id}' created");

        var removed = InventoryManager.RemoveItem(item);

        if (!removed)
        {
            Debug.LogError($"Unable to remove item {item.id}");
            return;
        }

        Debug.Log($"Item {item.id} successfully removed. Its discarded value is {item.discarded}");
    }

    // Called if Game Foundation initialization fails 
    void OnInitFailed(Exception error)
    {
        Debug.LogException(error);
    }
}