Yesterday we talked about the [Range] attribute which ensures that float/int values entered in the inspector are constrained to a certain range, thus ensuring valid input. However wouldn’t it be great to validate data for all properties, not just those of type float and int?

OnValidate is a callback when a script extending MonoBehaviour or ScriptableObject (not mentioned in the API) is loaded or the value of a property is changed in the inspector. Here we can use if statements or assertions to check that the inputted data is valid.

public class MyComponent : MonoBehaviour
{
  [SerializeField] private Button myButton;

  private void OnValidate()
  {
    Assert.IsNotNull(myButton, "Expected myButton to be not null");
  }
}

50 Unity Tips #16: OnValidate

Further Reading