None<T> class

A type that represents the absence of a value.

Pattern matching is recommended for working with Option types.

Option<int> foo = None();

if (foo case None()) {
  print('No value!');
}

Inheritance

• Object
• Option<T>
• None

Available extensions

• OptionFlatten
• OptionTranspose
• OptionUnzip

Constructors

None()

const

Properties

hashCode → int

The hash code for this object.

no setter, inherited

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.

inherited

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.

inherited

call() → T

Shortcut to call Option.unwrap().

inherited

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.

inherited

inspect(void fn(T)) → Option<T>

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

inherited

isNone() → bool

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

inherited

isSome() → bool

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

inherited

isSomeAnd(bool predicate(T)) → bool

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

inherited

iter() → Iterable<T>

Returns an Iterable of the held value.

inherited

map<U>(U mapFn(T)) → Option<U>

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

inherited

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).

inherited

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()).

inherited

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.

inherited

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

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

inherited

or(Option<T> other) → Option<T>

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

inherited

orElse(Option<T> fn()) → Option<T>

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

inherited

toString() → String

A string representation of this object.

inherited

unwrap() → T

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

inherited

unwrapOr(T orValue) → T

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

inherited

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.

inherited

where(bool predicate(T)) → Option<T>

Filters this Option based on the given predicate function.

inherited

xor(Option<T> other) → Option<T>

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

inherited

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

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

inherited

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

Zips this Option with another Option using the given function.

inherited

Operators

operator ==(Object other) → bool

Compare equality between two Option values.

inherited

operator ~() → T

Deprecated: Use Option.call() as value() to easily unwrap Option type values instead.

inherited