UnitySerialized

A way to use a [SerializeField] attribute on interfaces in Unity

This repository contains sample code from my answer on the Unity forum:
https://forum.unity.com/threads/serialized-interface-fields.1238785/#post-9469838

A copy of the answer is below.

Hey guys,

Since Unity is in no hurry to please us with useful updates. I can only suggest you to use the following lifehack method for [SerializeField] links to interfaces.

You need to put this class to your scripts folder.

[DefaultExecutionOrder(-1000)]
public abstract class ComponentPicker<T> : MonoBehaviour
{
    public T Value { get; private set; }
 
    protected virtual void Awake()
    {
        Value = GetComponent<T>();
    }
}

For each interface type you want to serialize you will need to create a separate MonoBehaviour class.

For example you have:

public interface IGroundDetector
{
    public bool IsGrounded { get; }
}

public class DistanceGroundDetector : MonoBehaviour, IGroundDetector
{
    [field: SerializeField]
    public bool IsGrounded { get; private set; }

    [field: SerializeField]
    private float _detectionDistance = 0.01f;
 
    private void FixedUpdate()
    {
        IsGrounded = Physics.Raycast(transform.position, Vector3.down, _detectionDistance);
    }
}

If you want to reference your IGroundDetector you can simply create a ComponentPicker for that and attach this component to GroundDetector GameObject.

Like that:

public class GroundDetectorPicker : ComponentPicker<IGroundDetector>
{}

Now you can put a reference to picker component and take a value from that!

Usage example:

public class Test : MonoBehaviour
{
    [SerializeField]
    private GroundDetectorPicker _groundDetectorPicker;

    private void Update()
    {
        Debug.Log(_groundDetectorPicker.Value.IsGrounded);
    }
}