BaseField<T0>.onValidateValue

Description

An event raised to validate or adjust the field's value before committing it.

Use this event to modify or validate a value before committing it. For example, you can clamp, sanitize, or replace the input value to match specific constraints. To reject an input value, return a fallback such as the current BaseField<T0>.value.

Registered callbacks run whenever the field's value changes, either through the BaseField<T0>.value setter or BaseField<T0>.SetValueWithoutNotify. The value returned by each callback replaces the incoming value and is then stored. If the change occurs from the BaseField<T0>.value setter, it reports the stored value as ChangeEvent<T0>.newValue. If the change occurs from BaseField<T0>.SetValueWithoutNotify, it doesn't report a ChangeEvent<T0>.

If you register more than one callback, they compose in their registration order. Each callback receives the previous callback's result, and the final result is stored and reported.

To assign a value while bypassing these callbacks, wrap the assignment in BaseField<T0>.IgnoreValidation.


The following example clamps a field's value to a maximum before returning it:

using UnityEngine;
using UnityEngine.UIElements;

namespace MyNamespace
{
    public class BaseFieldValidateValueExample
    {
        // Clamps the field's value to a maximum before it is committed.
        public IntegerField CreateCappedField()
        {
            var field = new IntegerField("Capped value");
            const int max = 1000;

            field.onValidateValue += v => Mathf.Min(v, max);

            return field;
        }
    }
}