Class RequiredAttribute

Marks a serialized field as required and displays a warning message box in the Unity Inspector whenever the field's value is considered unset or empty.

Inheritance
object
Attribute
PropertyAttribute
RequiredAttribute
Inherited Members
PropertyAttribute.order
PropertyAttribute.applyToCollection
Namespace: Scylla.Core.Attributes
Assembly: ScyllaCore.dll
Syntax
[AttributeUsage(AttributeTargets.Field)]
public sealed class RequiredAttribute : PropertyAttribute
Remarks

The warning box is rendered above the field itself, making it immediately visible to designers and developers who have not yet assigned the required value. The decorated field remains editable; the attribute provides visual feedback only.

The following field types are supported, and the emptiness check is type-specific:

  • Object references (UnityEngine.Object subclasses and ExposedReference) - considered empty when null or destroyed.
  • string - considered empty when null or whitespace-free zero-length string (string.IsNullOrEmpty).
  • Managed references ([SerializeReference]) - considered empty when null.
  • Arrays and lists - considered empty when the array contains zero elements.
  • All other serialized types (numeric, struct, etc.) - never considered empty; the warning is not shown.

This attribute provides Editor-only validation feedback. For runtime null-guard checks, enforce requirements with explicit code assertions or framework validation. 

public class Player : MonoBehaviour
{
    /* Warning: "SpawnPoint is required" displayed when not assigned */
    [Required]
    [SerializeField] private Transform _spawnPoint;

/* Warning with a domain-specific error message */
[Required("Player name must be set before entering a multiplayer session.")]
[SerializeField] private string _playerName;

/* Required array - warns when the array is empty */
[Required("At least one spawn location is required.")]
[SerializeField] private Transform[] _spawnLocations;



}

Constructors

RequiredAttribute()

Marks the decorated field as required. The Inspector displays a default warning message derived from the field's display name when the field is empty.

Declaration
public RequiredAttribute()

RequiredAttribute(string)

Marks the decorated field as required with a specific, user-defined warning message to display when the field is empty.

Declaration
public RequiredAttribute(string errorMessage)
Parameters
Type Name Description
string errorMessage

The warning text to display in the Inspector when the field has no value assigned. Use this to provide actionable guidance, such as where to find the asset to assign, why the field is mandatory, or what consequence an unassigned field will have at runtime. Passing null or an empty string causes the drawer to fall back to the auto-generated default message.

Properties

ErrorMessage

Gets the custom warning message displayed in the Inspector when the field's value is considered unset or empty.

Declaration
public string ErrorMessage { get; }
Property Value
Type Description
string

A custom error message string, or null if the default generated message should be used.
Remarks

When null, the Inspector drawer generates a default message from the field's display name in the format "{FieldName} is required". Provide a non-null string to replace the generated message with a more descriptive, context-specific explanation.

Extension Methods

See Also