validate abstract method

String? validate(
  1. String? value, {
  2. BuildContext? context,
})

Validates the given value. Returns an error message String if validation fails, otherwise returns `null].

The context can optionally be used by rules needing access to localization, etc. This context is provided by the FieldValidator when getValidator is called.

Implementation

String? validate(String? value, {BuildContext? context});