scala

class Option

[source: scala/Option.scala]

sealed abstract class Option[+A]
extends Product
This class represents optional values. Instances of Option are either instances of case class Some or it is case object None.
Author
Martin Odersky
Matthias Zenger
Version
1.1, 16/01/2007
Direct Known Subclasses:
Some, None

Method Summary
def elements : Iterator[A]
An singleton iterator returning the option's value if it is nonempty or the empty iterator if the option is empty.
def filter (p : (A) => Boolean) : Option[A]
If the option is nonempty and the given predicate p yields false on its value, return None. Otherwise return the option value itself.
def flatMap [B](f : (A) => Option[B]) : Option[B]
If the option is nonempty, return a function applied to its value. Otherwise return None.
def foreach (f : (A) => Unit) : Unit
Apply the given procedure f to the option's value, if it is nonempty. Do nothing if it is empty.
abstract def get : A
get the value of this option. @requires that the option is nonEmpty.
def get [B >: A](default : B) : B
def getOrElse [B >: A](default : => B) : B
If the option is nonempty return its value, otherwise return the result of evaluating a default expression.
def isDefined : Boolean
True if the option is a Some(...) false otherwise.
abstract def isEmpty : Boolean
True if the option is the None value, false otherwise.
def map [B](f : (A) => B) : Option[B]
If the option is nonempty, return a function applied to its value, wrapped in a Some i.e. Some(f(this.get)). Otherwise return None.
def orElse [B >: A](alternative : => Option[B]) : Option[B]
If the option is nonempty return it, otherwise return the result of evaluating an alternative expression.
def toList : List[A]
A singleton list containing the option's value if it is nonempty or the empty list if the option is empty.
Methods inherited from Product
productElement (abstract), productArity (abstract), element, arity, productPrefix
Methods inherited from AnyRef
getClass, hashCode, equals, clone, toString, notify, notifyAll, wait, wait, wait, finalize, ==, !=, eq, ne, synchronized
Methods inherited from Any
==, !=, isInstanceOf, asInstanceOf
Method Details
abstract def isEmpty : Boolean
True if the option is the None value, false otherwise.

def isDefined : Boolean
True if the option is a Some(...) false otherwise.

abstract def get : A
get the value of this option. @requires that the option is nonEmpty.
Throws
Predef.NoSuchElementException - if the option is empty.

@deprecated

def get[B >: A](default : B) : B
Deprecated
; use getOrElse instead

def getOrElse[B >: A](default : => B) : B
If the option is nonempty return its value, otherwise return the result of evaluating a default expression.
Parameters
default - the default expression.

def map[B](f : (A) => B) : Option[B]
If the option is nonempty, return a function applied to its value, wrapped in a Some i.e. Some(f(this.get)). Otherwise return None.
Parameters
f - the function to apply

def flatMap[B](f : (A) => Option[B]) : Option[B]
If the option is nonempty, return a function applied to its value. Otherwise return None.
Parameters
f - the function to apply

def filter(p : (A) => Boolean) : Option[A]
If the option is nonempty and the given predicate p yields false on its value, return None. Otherwise return the option value itself.
Parameters
p - the predicate used for testing.

def foreach(f : (A) => Unit) : Unit
Apply the given procedure f to the option's value, if it is nonempty. Do nothing if it is empty.
Parameters
f - the procedure to apply.

def orElse[B >: A](alternative : => Option[B]) : Option[B]
If the option is nonempty return it, otherwise return the result of evaluating an alternative expression.
Parameters
alternative - the alternative expression.

def elements : Iterator[A]
An singleton iterator returning the option's value if it is nonempty or the empty iterator if the option is empty.

def toList : List[A]
A singleton list containing the option's value if it is nonempty or the empty list if the option is empty.