None<T extends Object> class

Type None<T> is an Option that does not contain any value.

You can construct a None using the None() constructor or by calling the Option.none() factory constructor. A None is also returned when a null is passed to the Option.some() factory constructor.

Inheritance

Constructors

None()
Create a None option with no value.
const

Properties

hashCode → int
The hash code for this object.
no setterinherited
props → List<Object>
The list of properties that will be used to determine whether two instances are equal.
no setter
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
stringify → bool?
If set to true, the toString method will be overridden to output this instance's props.
no setterinherited

Methods

and<U extends Object>(Option<U> optb) → Option<U>
Returns None if the option is None, otherwise returns optb.
inherited
andThen<U extends Object>(Option<U> op(T)) → Option<U>
Returns None if the option is None, otherwise calls op with the wrapped value and returns the result.
inherited
expect(String msg) → T
Unwraps an option, yielding the content of a Some.
inherited
filter(bool predicate(T)) → Option<T>
Returns None if the option is None, otherwise calls predicate with the wrapped value and returns:
inherited
isNone() → bool
Returns true if the option is a None value.
inherited
isSome() → bool
Returns true if the option is a Some value.
inherited
map<U extends Object>(U op(T)) → Option<U>
Maps an Option<T> to Option<U> by applying a function to a contained Some value. Otherwise returns a None.
inherited
mapOr<U>(U op(T), U opt) → U
Applies a function to the contained value (if any), or returns the provided default (if not).
inherited
mapOrElse<U>(U op(T), U def()) → U
Maps an Option<T> to U by applying a function to a contained T value, or computes a default (if not).
inherited
match<R>(R someop(T), R noneop()) → R
Invokes either the someop or the noneop depending on the option.
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
okOr<E extends Object>(E err) → Result<T, E>
Transforms the Option<T> into a Result<T, E>, mapping Some(v) to Ok(v) and None to Err(err).
inherited
okOrElse<E extends Object>(E err()) → Result<T, E>
Transforms the Option<T> into a Result<T, E>, mapping Some(v) to Ok(v) and None to Err(err()).
inherited
or(Option<T> optb) → Option<T>
Returns the option if it contains a value, otherwise returns optb.
inherited
orElse(Option<T> op()) → Option<T>
Returns the option if it contains a value, otherwise calls op and returns the result.
inherited
toNullable() → T?
Returns an nullable that represents this optional value.
toString() → String
A string representation of this object.
inherited
unwrap() → T
Unwraps an option, yielding the content of a Some.
inherited
unwrapOr(T opt) → T
Returns the contained value or a default.
inherited
unwrapOrElse(T op()) → T
Returns the contained value or computes it from a closure.
inherited
when<R>({required R some(T), required R none()}) → R
Invokes either some or none depending on the option.
inherited
xor(Option<T> optb) → Option<T>
Returns Some if exactly one of this, optb is Some, otherwise returns None.
inherited

Operators

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