Game Foundation Tutorials

Playing with stats at runtime

In the previous tutorial, we learned how to configure mutable properties in the Stat Detail, using Stat Definitions.

In this one, we'll take a look at the code to get the stat definition, and modify its value for an item instance.

Prerequisites

We'll start from the end of the inventory tutorial. If you didn't follow this tutorial, please copy/paste the final source code in to a class file named GFInit.cs and associate it to a new GameObject of the new scene.

Getting the stat definition

Open your GFInit.cs file and append the following code inside OnInitSucceeded:

var item = InventoryManager.CreateItem(definition);

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

// <---- Insert the following code here

// Gets the stat catalog
var statCatalog = GameFoundation.catalogs.statCatalog;

// This is the id of the stat definition we've created
const string statDefinitionId = "myIntStat";

// Gets the stat definition from the catalog
var statDefinition = statCatalog.FindStatDefinition(statDefinitionId);

if (statDefinition is null)
{
    Debug.LogError($"Cannot find the {nameof(StatDefinition)} {statDefinitionId}");
    return;
}

Debug.Log($"{nameof(StatDefinition)} '{statDefinition.displayName}' found");

Compile and start the scene. You should see the following log entry:

! StatDefinition 'My Int Stat' found

Getting the default value of the stat

You can retrieve the default value of a stat definition within an item definition as following. Back to your code, append the follow code:

// Gets the detail from the item definition
var statDetail = item.definition.GetDetail<StatDetail>();

// Gets the default value from the detail
var defaultValue = statDetail.GetDefaultValue(statDefinition);

Debug.Log($"The default value of '{statDefinition.displayName}' is {defaultValue}");

Compile and start the scene. You should see the following log entry:

! The default value of 'My Int Stat' is 42

Getting the current value of the stat for an item instance

While the default value of a stat cannot be changed, the item instance can overwrite it.

Append the following code:

// Tries to get the value of the stat for the created item
var found = StatManager.TryGetValue(item, statDefinition, out var statValue);
if (!found)
{
    Debug.LogError($"item '{item.definition.displayName}' doesn't seem to support the stat '{statDefinition.displayName}'");
}
else
{
    Debug.Log($"item '{item.definition.displayName}' value for '{statDefinition.displayName}' is {statValue}");
}

This new code should log the following message:

! Item 'My First Item' value for 'My Int Stat' is 42

As expected, the current value is the same as the default one. That's because we didn't play with it yet. That's what we are about to do, with the following code:

//StatManager.SetValue(item, statDefinition, 38);
item.SetStat(statDefinition, 38);

statValue = item.GetStat(statDefinition);

Debug.Log($"Item '{item.definition.displayName}' value for '{statDefinition.displayName}' is {statValue}");

The item also exposes GetStat/SetStat methods.

The StatManager will soon be merged to the Inventory Manager and only the API using the item as a base will remain.

Start your scene. Your console should have the following log:

! item 'My First Item' value for 'My Int Stat' is 38

As you can see, setting a stat is pretty straightforward.

Conclusion

Playing with static properties and mutable properties of your catalog items will help you build a better economy for your game.

Going forward

Speaking about economy, now is the time to turn your game into a successful business.

In the next tutorial, we'll talk about transactions. But we'll start smooth with the virtual transactions.

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");

        // ----------------> Beginning of this tutorial

        // Gets the stat catalog
        var statCatalog = GameFoundation.catalogs.statCatalog;

        // This is the id of the stat definition we've created
        const string statDefinitionId = "myIntStat";

        // Gets the stat definition from the catalog
        var statDefinition = statCatalog.FindStatDefinition(statDefinitionId);

        if (statDefinition is null)
        {
            Debug.LogError($"Cannot find the {nameof(StatDefinition)} {statDefinitionId}");
            return;
        }

        Debug.Log($"{nameof(StatDefinition)} '{statDefinition.displayName}' found.");

        // Gets the detail from the item definition
        var statDetail = item.definition.GetDetail<StatDetail>();

        // Gets the default value from the detail
        var defaultValue = statDetail.GetDefaultValue(statDefinition);

        Debug.Log($"The default value of '{statDefinition.displayName}' is {defaultValue}");

        // Tries to get the value of the stat for the created item
        var found = StatManager.TryGetValue(item, statDefinition, out var statValue);
        if (!found)
        {
            Debug.LogError($"Item '{item.definition.displayName}' doesn't seem to support the stat '{statDefinition.displayName}'");
        }
        else
        {
            Debug.Log($"Item '{item.definition.displayName}' value for '{statDefinition.displayName}' is {statValue}");
        }

        //StatManager.SetValue(item, statDefinition, 38);
        item.SetStat(statDefinition, 38);

        statValue = item.GetStat(statDefinition);

        Debug.Log($"Item '{item.definition.displayName}' value for '{statDefinition.displayName}' is {statValue}");

        // <---------------- End of this tutorial

        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);
    }
}