ScriptableSingleton doesn't load saved data

Question

I am trying to create a ScriptableSingleton to save certain values for a tool window I developed. The data is saved and loaded as long as Unity is running, but after exiting and restarting Unity, the saved data is not loaded. Is there a solution?

ScriptableSingleton Code:

using UnityEditor;

[FilePath("ProjectSettings/Test.asset", FilePathAttribute.Location.ProjectFolder)]
public class TestSaver : ScriptableSingleton<Test>
{
    private string testValue;

    public static string TestValue
    {
        get => instance.testValue;
        set
        {
            if(instance.testValue != value)
            {
                instance.testValue = value;
                instance.Save(true);
            }
        }
    }
}

Do you see the ProjectSettings/Test.asset file being created? If so, what are the contents of that file? — DMGregory
– DMGregory ♦, Commented Feb 13 at 23:55
Also, I notice you've defined this as TestSaver : ScriptableSingleton<Test> but haven't shown us the Test type. Did you mean to write TestSaver : ScriptableSingleton<TestSaver>, using the curiously recurring template pattern as shown in the docs? — DMGregory
– DMGregory ♦, Commented Feb 14 at 3:57

Philipp · Accepted Answer · 2025-02-14 09:59:55Z

First of all, as DMGregory wrote in a comment, a class inheriting from ScriptableSingleton should have itself as the generic parameter to ScriptableSingleton, not some other class. So the class declaration should probably be:

 public class TestSaver : ScriptableSingleton<TestSaver>

(Not sure what the class Test does in your project, because you didn't post it. But if it contains the state you want to persist, then that should probably be moved to TestSaver. Or maybe it should be referenced by TestSaver).

Then there is another problem. As the documentation for ScriptableSingleton says:

Also, if the class uses the FilePathAttribute, the serializable data persists between sessions of Unity.

What does "serializable data" mean? This is explained in the manual section about serialization. But the tl;dr version is that if you want variables of the singleton to be serialized to the file for persistence, then you need to either declare them as public or mark them with the [SerializeField] attribute.

Check out the official example in the documentation for ScriptableSingleton. You will notice that they added this attribute to all the variables they want to persist.

So changing the line

private string testValue;

to this:

[SerializeField] private string testValue;

should do the trick.

Thank you, I should have mark it with the [SerializeField]. — Ahmed Dyaa
– Ahmed Dyaa, Commented Feb 14 at 12:41
Another very important issue, the file should have the exact same name as the ScriptableSingleton class (TestSaver.cs here). Like all MonoBehaviour and ScriptableObject, unity will explode if the script and files don't have matching names — Lou Garczynski
– Lou Garczynski, Commented Nov 18 at 18:33

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