Option<T> class sealed

Optional value wrapper for Rust-style present-or-absent values.

Use None() when no value is present, and Some(value) when a value is present even if that value is null.

const nickname = Some<String?>(null);

final label = switch (nickname) {
  None<String?>() => 'missing',
  Some<String?>(:final value) => value ?? 'present null',
};

Available extensions

Constructors

Option.fromNullable(T? value): Wraps a nullable value: null becomes None, anything else Some.
factory

Properties

hashCode → int: The hash code for this object.
no setterinherited
isNone → bool: Whether this option is None.
no setter
isSome → bool: Whether this option is Some.
no setter
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited

Methods

and<R>(Option<R> other) → Option<R>: Available on Option<T>, provided by the OptionTransform extension
Returns other when this option is present, and None otherwise.
andThen<R>(Option<R> next(T value)) → Option<R>: Chains another option-producing operation when a value is present.
contains(T value) → bool: Available on Option<T>, provided by the OptionQuery extension
Whether this option holds a value equal to value.
expect(String message) → T: Available on Option<T>, provided by the OptionQuery extension
Returns the present value, or throws message when absent.
filter(bool predicate(T value)) → Option<T>: Available on Option<T>, provided by the OptionTransform extension
Keeps a present value only when it satisfies predicate.
flatten() → Option<T>: Available on Option<Option<T>>, provided by the OptionFlatten extension
Turns Some(Some(value)) into Some(value), and any absence into None.
inspect(void action(T value)) → Option<T>: Available on Option<T>, provided by the OptionTransform extension
Calls action with a present value, and returns this option unchanged.
isNoneOr(bool predicate(T value)) → bool: Available on Option<T>, provided by the OptionQuery extension
Whether the option is absent, or its value satisfies predicate.
isSomeAnd(bool predicate(T value)) → bool: Available on Option<T>, provided by the OptionQuery extension
Whether a value is present and satisfies predicate.
map<R>(R mapper(T value)) → Option<R>: Maps a present value and leaves absent values unchanged.
mapOr<R>(R fallback, R mapper(T value)) → R: Available on Option<T>, provided by the OptionTransform extension
Maps a present value, or returns fallback when absent.
mapOrElse<R>(R fallback(), R mapper(T value)) → R: Available on Option<T>, provided by the OptionTransform extension
Maps a present value, or computes a fallback when absent.
match<R>({required R some(T value), required R none()}) → R: Pattern matches this option.
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
okOr<E>(E error) → Result<T, E>: Available on Option<T>, provided by the OptionCombine extension
Returns Ok with a present value, or Err with error when absent.
okOrElse<E>(E error()) → Result<T, E>: Available on Option<T>, provided by the OptionCombine extension
Returns Ok with a present value, or computes an Err when absent.
or(Option<T> other) → Option<T>: Available on Option<T>, provided by the OptionTransform extension
Returns this option when present, and other otherwise.
orElse(Option<T> fallback()) → Option<T>: Available on Option<T>, provided by the OptionTransform extension
Returns this option when present, and computes one otherwise.
toIterable() → Iterable<T>: Available on Option<T>, provided by the OptionQuery extension
Returns the present value as a one-element iterable, or an empty one.
toNullable() → T?: Available on Option<T>, provided by the OptionQuery extension
Returns the present value, or null when absent.
toString() → String: A string representation of this object.
inherited
transpose() → Result<Option<T>, E>: Available on Option<Result<T, E>>, provided by the OptionTranspose extension
Turns an optional result into a result of an option.
unwrap() → T: Available on Option<T>, provided by the OptionQuery extension
Returns the present value, or throws when absent.
unwrapOr(T fallback) → T: Returns the present value, or fallback when this option is absent.
unwrapOrElse(T fallback()) → T: Returns the present value, or computes one when this option is absent.
unzip() → (Option<A>, Option<B>): Available on Option<(A, B)>, provided by the OptionUnzip extension
Splits a present pair into two present options, and absence into two absent ones.
xor(Option<T> other) → Option<T>: Available on Option<T>, provided by the OptionTransform extension
Returns whichever of the two options is present, when exactly one is.
zip<U>(Option<U> other) → Option<(T, U)>: Available on Option<T>, provided by the OptionCombine extension
Pairs this value with other's, when both are present.
zipWith<U, R>(Option<U> other, R combine(T left, U right)) → Option<R>: Available on Option<T>, provided by the OptionCombine extension
Combines this value with other's, when both are present.

Operators

operator ==(Object other) → bool: The equality operator.
inherited

Option<T> class sealed

Constructors

Properties

Methods

Operators

server library