Option<T> class sealed

A type that represents the presence (Some) or absence (None) of a value.

Pattern matching is recommended for working with Option types.

Option<int> foo = Some(42);

print(switch (foo) {
  Some(value: var bar) => 'Some value: $bar',
  None() => 'No value!'
});

See also: Rust: Option

Implementers

• None
• Some

Available extensions

• OptionFlatten
• OptionTranspose
• OptionUnzip

Constructors

Option.from(T? value)

Creates an Option from the given nullable T value.

factory

Properties

hashCode → int

The hash code for this object.

no setter, override

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

and<U>(Option<U> other) → Option<U>

Returns None<U> if this Option is None<T>, otherwise returns other.

andThen<U>(Option<U> fn(T)) → Option<U>

Returns None<U> if this Option is None<T>, otherwise calls fn with the held value and returns the returned Option.

call() → T

Shortcut to call Option.unwrap().

expect(String message) → T

Returns the held value of this Option if it is Some, or throws OptionError with the given message if this Option is None.

inspect(void fn(T)) → Option<T>

Calls the provided function with the contained value if this Option is Some.

isNone() → bool

Returns whether or not this Option holds no value (None).

isSome() → bool

Returns whether or not this Option holds a value (Some).

isSomeAnd(bool predicate(T)) → bool

Returns whether or not this Option holds a value (Some) and the held value matches the given predicate.

iter() → Iterable<T>

Returns an Iterable of the held value.

map<U>(U mapFn(T)) → Option<U>

Maps this Option<T> to an Option<U> using the given function with the held value.

mapOr<U>(U orValue, U mapFn(T)) → Option<U>

Maps this Option<T> to an Option<U> using the given function with the held value if this Option<T> is Some. Otherwise returns the provided orValue as Some(orValue).

mapOrElse<U>(U orFn(), U mapFn(T)) → Option<U>

Maps this Option<T> to an Option<U> using the given mapFn function with the held value if this Option is Some. Otherwise returns the result of orFn as Some(orFn()).

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

okOr<E>(E err) → Result<T, E>

Converts this Option<T> into a Result<T, E> using the given err if None.

okOrElse<E>(E elseFn()) → Result<T, E>

Converts this Option<T> into a Result<T, E> using the returned value from elseFn if None.

or(Option<T> other) → Option<T>

Returns this Option if this Option is Some<T>, otherwise returns other.

orElse(Option<T> fn()) → Option<T>

Returns this Option if this Option is Some<T>, otherwise calls fn and returns the returned Option.

toString() → String

A string representation of this object.

override

unwrap() → T

Returns the held value of this Option if it is Some.

unwrapOr(T orValue) → T

Returns the held value of this Option if it is Some, or the given value if this Option is None.

unwrapOrElse(T elseFn()) → T

Returns the held value of this Option if it is Some, or returns the returned value from elseFn if this Option is None.

where(bool predicate(T)) → Option<T>

Filters this Option based on the given predicate function.

xor(Option<T> other) → Option<T>

Returns Some if exactly one of this Option and other is Some, otherwise returns None.

zip<U>(Option<U> other) → Option<(T, U)>

Zips this Option with another Option, returning a Record of their held values.

zipWith<U, V>(Option<U> other, V zipFn(T, U)) → Option<V>

Zips this Option with another Option using the given function.

Operators

operator ==(Object other) → bool

Compare equality between two Option values.

override