Scala 3
3.5.2
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Copyright (c) 2002-2024, LAMP/EPFL
Copyright (c) 2002-2024, LAMP/EPFL
Scala 3/scala/None

None

scala.None
case object None extends Option[Nothing]

This case object represents non-existent values.

Attributes

Source
Option.scala
Graph
Supertypes
class Option[Nothing]
trait Serializable
trait Product
trait Equals
class Object
trait Matchable
class Any
Show all
Self type
None.type

Members list

Type members

Inherited classlikes

class WithFilter(p: A => Boolean)

We need a whole WithFilter class to honor the "doesn't create a new collection" contract even though it seems unlikely to matter much in a collection with max size 1.

We need a whole WithFilter class to honor the "doesn't create a new collection" contract even though it seems unlikely to matter much in a collection with max size 1.

Attributes

Inherited from:
Option
Source
Option.scala
Supertypes
class Object
trait Matchable
class Any

Value members

Concrete methods

def get: Nothing

Returns the option's value.

Returns the option's value.

This is equivalent to:

option match {
 case Some(x) => x
 case None    => throw new Exception
}

Attributes

Throws

NoSuchElementException if the option is empty.

Note

The option must be nonempty.

Source
Option.scala

Inherited methods

final def collect[B](pf: PartialFunction[Nothing, B]): Option[B]

Returns a scala.Some containing the result of applying pf to this scala.Option's contained value, if this option is nonempty and pf is defined for that value.

Returns a scala.Some containing the result of applying pf to this scala.Option's contained value, if this option is nonempty and pf is defined for that value. Returns None otherwise.

Value parameters

pf

the partial function.

Attributes

Returns

the result of applying pf to this scala.Option's value (if possible), or None.

Example 

// Returns Some(HTTP) because the partial function covers the case.
Some("http") collect {case "http" => "HTTP"}
// Returns None because the partial function doesn't cover the case.
Some("ftp") collect {case "http" => "HTTP"}
// Returns None because the option is empty. There is no value to pass to the partial function.
None collect {case value => value}
Inherited from:
Option
Source
Option.scala
final def contains[A1](elem: A1): Boolean

Tests whether the option contains a given value as an element.

Tests whether the option contains a given value as an element.

This is equivalent to:

option match {
 case Some(x) => x == elem
 case None    => false
}

Value parameters

elem

the element to test.

Attributes

Returns

true if the option has an element that is equal (as determined by ==) to elem, false otherwise.

Example 

// Returns true because Some instance contains string "something" which equals "something".
Some("something") contains "something"
// Returns false because "something" != "anything".
Some("something") contains "anything"
// Returns false when method called on None.
None contains "anything"
Inherited from:
Option
Source
Option.scala
final def exists(p: Nothing => Boolean): Boolean

Returns true if this option is nonempty and the predicate p returns true when applied to this scala.Option's value.

Returns true if this option is nonempty and the predicate p returns true when applied to this scala.Option's value. Otherwise, returns false.

This is equivalent to:

option match {
 case Some(x) => p(x)
 case None    => false
}

Value parameters

p

the predicate to test

Attributes

Inherited from:
Option
Source
Option.scala
final def filter(p: Nothing => Boolean): Option[Nothing]

Returns this scala.Option if it is nonempty and applying the predicate p to this scala.Option's value returns true.

Returns this scala.Option if it is nonempty and applying the predicate p to this scala.Option's value returns true. Otherwise, return None.

This is equivalent to:

option match {
 case Some(x) if p(x) => Some(x)
 case _               => None
}

Value parameters

p

the predicate used for testing.

Attributes

Inherited from:
Option
Source
Option.scala
final def filterNot(p: Nothing => Boolean): Option[Nothing]

Returns this scala.Option if it is nonempty and applying the predicate p to this scala.Option's value returns false.

Returns this scala.Option if it is nonempty and applying the predicate p to this scala.Option's value returns false. Otherwise, return None.

This is equivalent to:

option match {
 case Some(x) if !p(x) => Some(x)
 case _                => None
}

Value parameters

p

the predicate used for testing.

Attributes

Inherited from:
Option
Source
Option.scala
final def flatMap[B](f: Nothing => Option[B]): Option[B]

Returns the result of applying f to this scala.Option's value if this scala.Option is nonempty.

Returns the result of applying f to this scala.Option's value if this scala.Option is nonempty. Returns None if this scala.Option is empty. Slightly different from map in that f is expected to return an scala.Option (which could be None).

This is equivalent to:

option match {
 case Some(x) => f(x)
 case None    => None
}

Value parameters

f

the function to apply

Attributes

See also

map

foreach

Inherited from:
Option
Source
Option.scala
def flatten[B](implicit ev: Nothing <:< Option[B]): Option[B]

Returns the nested scala.Option value if it is nonempty.

Returns the nested scala.Option value if it is nonempty. Otherwise, return None.

This is equivalent to:

option match {
 case Some(Some(b)) => Some(b)
 case _             => None
}

Value parameters

ev

an implicit conversion that asserts that the value is also an scala.Option.

Attributes

See also

flatMap

Example 

Some(Some("something")).flatten
Inherited from:
Option
Source
Option.scala
final def fold[B](ifEmpty: => B)(f: Nothing => B): B

Returns the result of applying f to this scala.Option's value if the scala.Option is nonempty.

Returns the result of applying f to this scala.Option's value if the scala.Option is nonempty. Otherwise, evaluates expression ifEmpty.

This is equivalent to:

option match {
 case Some(x) => f(x)
 case None    => ifEmpty
}

This is also equivalent to:

option map f getOrElse ifEmpty

Value parameters

f

the function to apply if nonempty.

ifEmpty

the expression to evaluate if empty.

Attributes

Inherited from:
Option
Source
Option.scala
final def forall(p: Nothing => Boolean): Boolean

Returns true if this option is empty or the predicate p returns true when applied to this scala.Option's value.

Returns true if this option is empty or the predicate p returns true when applied to this scala.Option's value.

This is equivalent to:

option match {
 case Some(x) => p(x)
 case None    => true
}

Value parameters

p

the predicate to test

Attributes

Inherited from:
Option
Source
Option.scala
final def foreach[U](f: Nothing => U): Unit

Apply the given procedure f to the option's value, if it is nonempty.

Apply the given procedure f to the option's value, if it is nonempty. Otherwise, do nothing.

This is equivalent to:

option match {
 case Some(x) => f(x)
 case None    => ()
}

Value parameters

f

the procedure to apply.

Attributes

See also

map

flatMap

Inherited from:
Option
Source
Option.scala
final def getOrElse[B](default: => B): B

Returns the option's value if the option is nonempty, otherwise return the result of evaluating default.

Returns the option's value if the option is nonempty, otherwise return the result of evaluating default.

This is equivalent to:

option match {
 case Some(x) => x
 case None    => default
}

Value parameters

default

the default expression.

Attributes

Inherited from:
Option
Source
Option.scala
final def isDefined: Boolean

Returns true if the option is an instance of scala.Some, false otherwise.

Returns true if the option is an instance of scala.Some, false otherwise.

This is equivalent to:

option match {
 case Some(_) => true
 case None    => false
}

Attributes

Inherited from:
Option
Source
Option.scala
final def isEmpty: Boolean

Returns true if the option is None, false otherwise.

Returns true if the option is None, false otherwise.

This is equivalent to:

option match {
 case Some(_) => false
 case None    => true
}

Attributes

Inherited from:
Option
Source
Option.scala
def iterator: Iterator[Nothing]

Returns a singleton iterator returning the scala.Option's value if it is nonempty, or an empty iterator if the option is empty.

Returns a singleton iterator returning the scala.Option's value if it is nonempty, or an empty iterator if the option is empty.

Attributes

Inherited from:
Option
Source
Option.scala
final override def knownSize: Int

The number of elements in this option, if it can be cheaply computed, -1 otherwise.

The number of elements in this option, if it can be cheaply computed, -1 otherwise. Cheaply usually means: Not requiring a collection traversal.

Attributes

Definition Classes
Inherited from:
Option
Source
Option.scala
final def map[B](f: Nothing => B): Option[B]

Returns a scala.Some containing the result of applying f to this scala.Option's value if this scala.Option is nonempty.

Returns a scala.Some containing the result of applying f to this scala.Option's value if this scala.Option is nonempty. Otherwise return None.

This is equivalent to:

option match {
 case Some(x) => Some(f(x))
 case None    => None
}

Value parameters

f

the function to apply

Attributes

See also

flatMap

foreach

Note

This is similar to flatMap except here, f does not need to wrap its result in an scala.Option.

Inherited from:
Option
Source
Option.scala
final def nonEmpty: Boolean

Returns false if the option is None, true otherwise.

Returns false if the option is None, true otherwise.

This is equivalent to:

option match {
 case Some(_) => true
 case None    => false
}

Attributes

Note

Implemented here to avoid the implicit conversion to Iterable.

Inherited from:
Option
Source
Option.scala
final def orElse[B](alternative: => Option[B]): Option[B]

Returns this scala.Option if it is nonempty, otherwise return the result of evaluating alternative.

Returns this scala.Option if it is nonempty, otherwise return the result of evaluating alternative.

This is equivalent to:

option match {
 case Some(x) => Some(x)
 case None    => alternative
}

Value parameters

alternative

the alternative expression.

Attributes

Inherited from:
Option
Source
Option.scala
final def orNull[A1](implicit ev: Null <:< A1): A1

Returns the option's value if it is nonempty, or null if it is empty.

Returns the option's value if it is nonempty, or null if it is empty.

Although the use of null is discouraged, code written to use scala.Option must often interface with code that expects and returns nulls.

This is equivalent to:

option match {
 case Some(x) => x
 case None    => null
}

Attributes

Example 

val initialText: Option[String] = getInitialText
val textField = new JComponent(initialText.orNull,20)
Inherited from:
Option
Source
Option.scala
def productElementNames: Iterator[String]

An iterator over the names of all the elements of this product.

An iterator over the names of all the elements of this product.

Attributes

Inherited from:
Product
Source
Product.scala
def productIterator: Iterator[Any]

An iterator over all the elements of this product.

An iterator over all the elements of this product.

Attributes

Returns

in the default implementation, an Iterator[Any]

Inherited from:
Product
Source
Product.scala
def stepper[S <: Stepper[_]](implicit shape: StepperShape[Nothing, S]): S

Returns a scala.collection.Stepper for the elements of this collection.

Returns a scala.collection.Stepper for the elements of this collection.

The Stepper enables creating a Java stream to operate on the collection, see scala.jdk.StreamConverters. For collections holding primitive values, the Stepper can be used as an iterator which doesn't box the elements.

The implicit scala.collection.StepperShape parameter defines the resulting Stepper type according to the element type of this collection.

Note that this method is overridden in subclasses and the return type is refined to S with EfficientSplit, for example scala.collection.IndexedSeqOps.stepper. For Steppers marked with scala.collection.Stepper.EfficientSplit, the converters in scala.jdk.StreamConverters allow creating parallel streams, whereas bare Steppers can be converted only to sequential streams.

Attributes

Inherited from:
IterableOnce
Source
IterableOnce.scala
final def toLeft[X](right: => X): Either[Nothing, X]

Returns a scala.util.Right containing the given argument right if this is empty, or a scala.util.Left containing this scala.Option's value if this scala.Option is nonempty.

Returns a scala.util.Right containing the given argument right if this is empty, or a scala.util.Left containing this scala.Option's value if this scala.Option is nonempty.

This is equivalent to:

option match {
 case Some(x) => Left(x)
 case None    => Right(right)
}

Value parameters

right

the expression to evaluate and return if this is empty

Attributes

See also

toRight

Inherited from:
Option
Source
Option.scala
def toList: List[Nothing]

Returns a singleton list containing the scala.Option's value if it is nonempty, or the empty list if the scala.Option is empty.

Returns a singleton list containing the scala.Option's value if it is nonempty, or the empty list if the scala.Option is empty.

This is equivalent to:

option match {
 case Some(x) => List(x)
 case None    => Nil
}

Attributes

Inherited from:
Option
Source
Option.scala
final def toRight[X](left: => X): Either[X, Nothing]

Returns a scala.util.Left containing the given argument left if this scala.Option is empty, or a scala.util.Right containing this scala.Option's value if this is nonempty.

Returns a scala.util.Left containing the given argument left if this scala.Option is empty, or a scala.util.Right containing this scala.Option's value if this is nonempty.

This is equivalent to:

option match {
 case Some(x) => Right(x)
 case None    => Left(left)
}

Value parameters

left

the expression to evaluate and return if this is empty

Attributes

See also

toLeft

Inherited from:
Option
Source
Option.scala
final def unzip[A1, A2](implicit asPair: Nothing <:< (A1, A2)): (Option[A1], Option[A2])

Converts an Option of a pair into an Option of the first element and an Option of the second element.

Converts an Option of a pair into an Option of the first element and an Option of the second element.

This is equivalent to:

option match {
  case Some((x, y)) => (Some(x), Some(y))
  case _            => (None,    None)
}

Type parameters

A1

the type of the first half of the element pair

A2

the type of the second half of the element pair

Value parameters

asPair

an implicit conversion which asserts that the element type of this Option is a pair.

Attributes

Returns

a pair of Options, containing, respectively, the first and second half of the element pair of this Option.

Inherited from:
Option
Source
Option.scala
final def unzip3[A1, A2, A3](implicit asTriple: Nothing <:< (A1, A2, A3)): (Option[A1], Option[A2], Option[A3])

Converts an Option of a triple into three Options, one containing the element from each position of the triple.

Converts an Option of a triple into three Options, one containing the element from each position of the triple.

This is equivalent to:

option match {
  case Some((x, y, z)) => (Some(x), Some(y), Some(z))
  case _               => (None,    None,    None)
}

Type parameters

A1

the type of the first of three elements in the triple

A2

the type of the second of three elements in the triple

A3

the type of the third of three elements in the triple

Value parameters

asTriple

an implicit conversion which asserts that the element type of this Option is a triple.

Attributes

Returns

a triple of Options, containing, respectively, the first, second, and third elements from the element triple of this Option.

Inherited from:
Option
Source
Option.scala
final def withFilter(p: Nothing => Boolean): WithFilter

Necessary to keep scala.Option from being implicitly converted to scala.collection.Iterable in for comprehensions.

Necessary to keep scala.Option from being implicitly converted to scala.collection.Iterable in for comprehensions.

Attributes

Inherited from:
Option
Source
Option.scala
final def zip[A1, B](that: Option[B]): Option[(A1, B)]

Returns a scala.Some formed from this option and another option by combining the corresponding elements in a pair.

Returns a scala.Some formed from this option and another option by combining the corresponding elements in a pair. If either of the two options is empty, None is returned.

This is equivalent to:

(option1, option2) match {
  case (Some(x), Some(y)) => Some((x, y))
  case _                  => None
}

Value parameters

that

the options which is going to be zipped

Attributes

Example 

// Returns Some(("foo", "bar")) because both options are nonempty.
Some("foo") zip Some("bar")
// Returns None because `that` option is empty.
Some("foo") zip None
// Returns None because `this` option is empty.
None zip Some("bar")
Inherited from:
Option
Source
Option.scala
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Copyright (c) 2002-2024, LAMP/EPFL
Copyright (c) 2002-2024, LAMP/EPFL