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
Available extensions

Constructors

None()
const

Properties

hashCode int
The hash code for this object.
no setterinherited
runtimeType Type
A representation of the runtime type of the object.
no setterinherited

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