Basic Usage

Let's continue with our Weather example (you can find it here).

The super-sealed classes (Weather, ValidWeather, InvalidWeather and InvalidWeatherValue) replicate the same functionality of modddels :

// NB : In these examples, the types of the variables/callback parameters is specified 
// only for the sake of showing their types to you. You don't need to do so.

final Weather weather = Weather.rainy(
  temperature: 12,
  rainIntensity: 0.9,
);

You can use isValid, toEither and toBroadEither :

bool isValid = weather.isValid;
Either<InvalidWeather, ValidWeather> either = weather.toEither;
Either<List<Failure>, ValidWeather> broadEither = weather.toBroadEither;

All pattern matching methods we've seen so far can be used too : map, mapValidity, maybeMap, mapOrNull, maybeMapValidity, mapInvalid, whenInvalid, etc... :

final message1 = weather.map(
  valid: (ValidWeather validWeather) => 'This weather is habitable',
  invalidValue: (InvalidWeatherValue invalidWeatherValue) =>
      invalidWeatherValue.habitableFailure.when(
    tooHot: () => "Humans would die of heat",
    tooCold: () => "Humans would freeze to death",
  ),
);

final message2 = weather.mapValidity(
  valid: (ValidWeather validWeather) => 'Valid weather',
  invalid: (InvalidWeather invalidWeather) => 'Invalid weather',
);

You can also access the failure(s) :

weather.mapOrNull(
  invalidValue: (InvalidWeatherValue invalidWeatherValue) {
    WeatherHabitableFailure failure = invalidWeatherValue.habitableFailure;
  },
);