Useful to validate if references to Object or GameObject match specific type in Unity

TypeValidationAttribute.cs

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Class)]
public class TypeValidationAttribute : PropertyAttribute
{
    public Type typeToValidate;

    public TypeValidationAttribute(Type typeToValidate)
    {
        this.typeToValidate = typeToValidate;
    }
}

[CustomPropertyDrawer(typeof(TypeValidationAttribute), true)]
public class TypeValidationPropertyDrawer: PropertyDrawer
{
    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
    {
        if (property.propertyType != SerializedPropertyType.ObjectReference)
        {
            EditorGUI.LabelField(position, $"Invalid usage of TypeValidation for field \"{label.text}\", use with Object references.");
            return;
        }

        var typeToValidate = (attribute as TypeValidationAttribute).typeToValidate;

        EditorGUI.BeginChangeCheck();
        EditorGUI.ObjectField(position, property, label);
        if (EditorGUI.EndChangeCheck())
        {
            var referencedObject =  property.objectReferenceValue;

            if (typeToValidate.IsInstanceOfType(referencedObject))
            {
                return;
            }

            if (referencedObject is GameObject gameObject)
            {
                var isValidType = gameObject.GetComponentInChildren(typeToValidate) != null;
                if (!isValidType)
                {
                    property.objectReferenceValue = null;
                    Debug.Log($"Invalid object, not an {typeToValidate.Name}.");
                }
            }
            else
            {
                property.objectReferenceValue = null;
                Debug.Log($"Invalid object, not an {typeToValidate.Name}.");
            }
        }


    }
}