ScriptableObject

What is a ScriptableObject?

A ScriptableObject is a data container that you can use to save large amounts of data, independent of class instances. One of the main use cases for ScriptableObjects is to reduce your Project’s memory usage by avoiding copies of values. This is useful if your Project has a PrefabAn asset type that allows you to store a GameObject complete with components and properties. The prefab acts as a template from which you can create new object instances in the scene. More info
See in Glossary that stores unchanging data in attached MonoBehaviour scriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
See in Glossary. Everytime you instantiate that Prefab, it will get its own copy of that data. Instead of using the method, and storing duplicated data, you can use a ScriptableObject to store the data and then access it by reference from all of the Prefabs. This means that there is one copy of the data in memory.

Just like MonoBehaviours, ScriptableObjects derive from the base Unity Object but, unlike MonoBehaviours, you can not attach a ScriptableObject to a GameObjectThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary. Instead, you save them as Assets in your Project.

When using the Editor, you can save data to ScriptableObjects while editing and at run time because ScriptableObjects use the Editor namespace and Editor scripting. In a deployed build, however, you can’t use ScriptableObjects to save data, but you can use the saved data from the ScriptableObject Assets that you set up during development. Data that you save from Editor Tools to ScriptableObjects as an asset is written to disk and is therefore persistent between sessions.

Using a ScriptableObject

The main use cases for ScriptableObjects are:

• Saving and storing data during an Editor session
• Saving data as an Asset in your Project to use at run time

To use a ScriptableObject, you need to create a script in your AssetsAny media or data that can be used in your game or Project. An asset may come from a file created outside of Unity, such as a 3D model, an audio file or an image. You can also create some asset types in Unity, such as an Animator Controller, an Audio Mixer or a Render Texture. More info
See in Glossary folder and make it inherit from the ScriptableObject class. You can use the CreateAssetMenu attribute to make it easy to create custom assets using your class. For example:

using UnityEngine;

[CreateAssetMenu(fileName = "Data", menuName = "ScriptableObjects/SpawnManagerScriptableObject", order = 1)]
public class SpawnManagerScriptableObject : ScriptableObject
{
    public string prefabName;

    public int numberOfPrefabsToCreate;
    public Vector3[] spawnPoints;
}

With the above script in your Assets folder, you can create an instance of your ScriptableObject by navigating to Assets > Create > ScriptableObjects > SpawnManagerScriptableObject. Give your new ScriptableObject instance a meaningful name and alter the values. To use these values, you need to create a new script that references your ScriptableObject, in this case, a SpawnManagerScriptableObject. For example:

using UnityEngine;

public class Spawner : MonoBehaviour
{
    // The GameObject to instantiate.
    public GameObject entityToSpawn;

    // An instance of the ScriptableObject defined above.
    public SpawnManagerScriptableObject spawnManagerValues;

    // This will be appended to the name of the created entities and increment when each is created.
    int instanceNumber = 1;

    void Start()
    {
        SpawnEntities();
    }

    void SpawnEntities()
    {
        int currentSpawnPointIndex = 0;

        for (int i = 0; i < spawnManagerValues.numberOfPrefabsToCreate; i++)
        {
            // Creates an instance of the prefab at the current spawn point.
            GameObject currentEntity = Instantiate(entityToSpawn, spawnManagerValues.spawnPoints[currentSpawnPointIndex], Quaternion.identity);

            // Sets the name of the instantiated entity to be the string defined in the ScriptableObject and then appends it with a unique number. 
            currentEntity.name = spawnManagerValues.prefabName + instanceNumber;

            // Moves to the next spawn point index. If it goes out of range, it wraps back to the start.
            currentSpawnPointIndex = (currentSpawnPointIndex + 1) % spawnManagerValues.spawnPoints.Length;

            instanceNumber++;
        }
    }
}

Attach the above script to a GameObject in your SceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary. Then, in the InspectorA Unity window that displays information about the currently selected GameObject, Asset or Project Settings, alowing you to inspect and edit the values. More info
See in Glossary, set the Spawn Manager Values field to be the new SpawnManagerScriptableObject that you set up. Set the Entity To Spawn field to be any Prefab in your Assets folder, and then click Play in the Editor. You will see the Prefab you referenced in the Spawner instantiated using the settings you set in the SpawnManagerScriptableObject. ableObject-derived class, you can use the CreateAssetMenu attribute to make it easy to create custom assets using your class.

Tip: When working with ScriptableObject references in the inspector, you can double click the reference field to open the inspector for your ScriptableObject. You can also create a custom Editor to define the look of the inspector for your type to help manage the data that it represents.

• 2018–10–15 Page published with editorial review