scala library 2.7.2.final API : scala.Option

scala.Option

class Option

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: - Matthias Zenger; - Martin Odersky
version: - 1.1, 16/01/2007

Companion: Option

Source: Option.scala(31)

Direct Known Subclasses

None

Some

Constructors

def this

Fields

elements

def elements

An singleton iterator returning the option's value if it is nonempty or the empty iterator if the option is empty

Iterator[A]

get

abstract def get

get the value of this option [details]

@requires that the option is nonEmpty.

throws: Predef.NoSuchElementException - if the option is empty.

isDefined

def isDefined

True if the option is a Some( [details]

..) false otherwise.

Boolean

isEmpty

abstract def isEmpty

True if the option is the None value, false otherwise

Boolean

productArity

abstract def productArity

return k for a product

A(x_1,
        
              [details]


                ..,x_k)

Int

Product

productPrefix

def productPrefix

By default the empty string [details]

Implementations may override this method in order to prepend a string prefix to the result of the toString methods.

String

Product

toList

def toList

A singleton list containing the option's value if it is nonempty or the empty list if the option is empty

List[A]

Methods

final def !=(arg0 : Any)

o != arg0 is the same as !(o == (arg0)) [details]

param: arg0 - the object to compare against this object for dis-equality.
return: - false if the receiver object is equivalent to the argument; true otherwise.

Boolean

Any

final def !=(arg0 : Object)

Boolean

AnyRef

final def ==(arg0 : Object)

o == arg0 is the same as

if (o eq null) arg0 eq null else o
        
              [details]


                equals(arg0)

param: arg0 - the object to compare against this object for equality.
return: - true if the receiver object is equivalent to the argument; false otherwise.

Boolean

AnyRef

final def ==(arg0 : Any)

o == arg0 is the same as

o
        
              [details]


                equals(arg0)

param: arg0 - the object to compare against this object for equality.
return: - true if the receiver object is equivalent to the argument; false otherwise.

Boolean

Any

asInstanceOf

final def asInstanceOf[T0]

This method is used to cast the receiver object to be of type T0 [details]

Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested typed.

return: - the receiver object.
throws: ClassCastException - if the receiver object is not an instance of erasure of type T0.

Any

clone

protected def clone

This method creates and returns a copy of the receiver object [details]

The default implementation of the clone method is platform dependent.

return: - a copy of the receiver object.

Object

AnyRef

final def eq(arg0 : Object)

This method is used to test whether the argument (arg0) is a reference to the receiver object (this) [details]

The eq method implements an equivalence relation on non-null instances of AnyRef:

It is reflexive: for any non-null instance x of type AnyRef, x.eq(x) returns true.
It is symmetric: for any non-null instances x and y of type AnyRef, x.eq(y) returns true if and only if y.eq(x) returns true.
It is transitive: for any non-null instances x, y, and z of type AnyRef if x.eq(y) returns true and y.eq(z) returns true, then x.eq(z) returns true.

Additionally, the eq method has three other properties.

It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
null.eq(null) returns true.

When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

param: arg0 - the object to compare against this object for reference equality.
return: - true if the argument is a reference to the receiver object; false otherwise.

Boolean

AnyRef

equals

def equals(arg0 : Any)

This method is used to compare the receiver object (this) with the argument object (arg0) for equivalence [details]

The default implementations of this method is an equivalence relation:

It is reflexive: for any instance x of type Any, x.equals(x) should return true.
It is symmetric: for any instances x and y of type Any, x.equals(y) should return true if and only if y.equals(x) returns true.
It is transitive: for any instances x, y, and z of type AnyRef if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.

If you override this method, you should verify that your implementation remains an equivalence relation. Additionally, when overriding this method it is often necessary to override hashCode to ensure that objects that are "equal" (o1.equals(o2) returns true) hash to the same Int (o1.hashCode.equals(o2.hashCode)).

param: arg0 - the object to compare against this object for equality.
return: - true if the receiver object is equivalent to the argument; false otherwise.

Boolean

AnyRef

filter

def filter(p : (A) => Boolean)

If the option is nonempty and the given predicate p yields false on its value, return None [details]

Otherwise return the option value itself.

param: p - the predicate used for testing.

Option[A]

finalize

protected def finalize

This method is called by the garbage collector on the receiver object when garbage collection determines that there are no more references to the object [details]

The details of when and if the finalize method are invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

Unit

AnyRef

flatMap

def flatMap[B](f : (A) => Option[B])

If the option is nonempty, return a function applied to its value [details]

Otherwise return None.

param: f - the function to apply

Option[B]

foreach

def foreach(f : (A) => Unit)

Apply the given procedure f to the option's value, if it is nonempty [details]

Do nothing if it is empty.

param: f - the procedure to apply.

Unit

get

def get[B >: A](default : B)

[details]

deprecated: - ; use getOrElse instead

getClass

final def getClass

Returns a representation that corresponds to the dynamic class of the receiver object [details]

The nature of the representation is platform dependent.

return: - a representation that corresponds to the dynamic class of the receiver object.

Class[Any]

AnyRef

getOrElse

def getOrElse[B >: A](default : => B)

If the option is nonempty return its value, otherwise return the result of evaluating a default expression [details]

param: default - the default expression.

hashCode

def hashCode

Returns a hash code value for the object [details]

The default hashing algorithm is platform dependent. Note that it is allowed for two objects to have identical hash codes (o1.hashCode.equals(o2.hashCode)) yet not be equal (o1.equals(o2) returns false). A degenerate implementation could always return 0. However, it is required that if two objects are equal (o1.equals(o2) returns true) that they have identical hash codes (o1.hashCode.equals(o2.hashCode)). Therefore, when overriding this method, be sure to verify that the behavior is consistent with the equals method.

return: - the hash code value for the object.

Int

AnyRef

isInstanceOf

final def isInstanceOf[T0]

This method is used to test whether the dynamic type of the receiver object is T0 [details]

Note that the test result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested typed.

return: - true if the receiver object is an instance of erasure of type T0; false otherwise.

Boolean

Any

map

def map[B](f : (A) => B)

If the option is nonempty, return a function applied to its value, wrapped in a Some i [details]

e. Some(f(this.get)). Otherwise return None.

param: f - the function to apply

Option[B]

final def ne(arg0 : Object)

o
        
              [details]


                ne(arg0)

is the same as !(o.eq(arg0)).

param: arg0 - the object to compare against this object for reference dis-equality.
return: - false if the argument is not a reference to the receiver object; true otherwise.

Boolean

AnyRef

notify

final def notify

Wakes up a single thread that is waiting on the receiver object's monitor

Unit

AnyRef

notifyAll

final def notifyAll

Wakes up all threads that are waiting on the receiver object's monitor

Unit

AnyRef

orElse

def orElse[B >: A](alternative : => Option[B])

If the option is nonempty return it, otherwise return the result of evaluating an alternative expression [details]

param: alternative - the alternative expression.

Option[B]

productElement

abstract def productElement(n : Int)

for a product

A(x_1,
        
              [details]


                ..,x_k)

, returns x_(n+1) for 0 <= n < k

param: n - the index of the element to return
return: - The element n elements after the first element

Any

Product

synchronized

final def synchronized[T0](arg0 : T0)

AnyRef

toLeft

def toLeft[X](right : => X)

An Either that is a Right with the given argument right if this is empty, or a Left if this is nonempty with the option's value

Either[A, X] with Product

toRight

def toRight[X](left : => X)

An Either that is a Left with the given argument left if this is empty, or a Right if this is nonempty with the option's value

Either[X, A] with Product

toString

def toString

Returns a string representation of the object [details]

The default representation is platform dependent.

return: - a string representation of the object.

String

AnyRef

wait

final def wait

Unit

AnyRef

wait

final def wait(arg0 : Long)

Unit

AnyRef

wait

final def wait(arg0 : Long, arg1 : Int)

Unit

AnyRef

elements	`def elements` An singleton iterator returning the option's value if it is nonempty or the empty iterator if the option is empty	Iterator[A]
get	`abstract def get` get the value of this option [details] @requires that the option is nonEmpty. throws `Predef.NoSuchElementException` - if the option is empty.	A
isDefined	`def isDefined` True if the option is a `Some`( [details] ..) false otherwise.	Boolean
isEmpty	`abstract def isEmpty` True if the option is the `None` value, false otherwise	Boolean
productArity	`abstract def productArity` return k for a product `A(x_1, [details]` `..,x_k)`	Int	Product
productPrefix	`def productPrefix` By default the empty string [details] Implementations may override this method in order to prepend a string prefix to the result of the toString methods.	String	Product
toList	`def toList` A singleton list containing the option's value if it is nonempty or the empty list if the option is empty	List[A]

!=	`final def !=(arg0 : Any)` `o != arg0` is the same as `!(o == (arg0))` [details] param `arg0` - the object to compare against this object for dis-equality. return - `false` if the receiver object is equivalent to the argument; `true` otherwise.	Boolean	Any
!=	`final def !=(arg0 : Object)`	Boolean	AnyRef
==	`final def ==(arg0 : Object)` `o == arg0` is the same as `if (o eq null) arg0 eq null else o [details]` `equals(arg0)`. param `arg0` - the object to compare against this object for equality. return - `true` if the receiver object is equivalent to the argument; `false` otherwise.	Boolean	AnyRef
==	`final def ==(arg0 : Any)` `o == arg0` is the same as `o [details]` `equals(arg0)`. param `arg0` - the object to compare against this object for equality. return - `true` if the receiver object is equivalent to the argument; `false` otherwise.	Boolean	Any
asInstanceOf	`final def asInstanceOf[T0]` This method is used to cast the receiver object to be of type `T0` [details] Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression `1.asInstanceOf[String]` will throw a `ClassCastException` at runtime, while the expression `List(1).asInstanceOf[List[String]]` will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested typed. return - the receiver object. throws `ClassCastException` - if the receiver object is not an instance of erasure of type `T0`.	T0	Any
clone	`protected def clone` This method creates and returns a copy of the receiver object [details] The default implementation of the `clone` method is platform dependent. return - a copy of the receiver object.	Object	AnyRef
eq	`final def eq(arg0 : Object)` This method is used to test whether the argument (`arg0`) is a reference to the receiver object (`this`) [details] The `eq` method implements an equivalence relation on non-null instances of `AnyRef`: It is reflexive: for any non-null instance `x` of type `AnyRef`, `x.eq(x)` returns `true`. It is symmetric: for any non-null instances `x` and `y` of type `AnyRef`, `x.eq(y)` returns `true` if and only if `y.eq(x)` returns `true`. It is transitive: for any non-null instances `x`, `y`, and `z` of type `AnyRef` if `x.eq(y)` returns `true` and `y.eq(z)` returns `true`, then `x.eq(z)` returns `true`. Additionally, the `eq` method has three other properties. It is consistent: for any non-null instances `x` and `y` of type `AnyRef`, multiple invocations of `x.eq(y)` consistently returns `true` or consistently returns `false`. For any non-null instance `x` of type `AnyRef`, `x.eq(null)` and `null.eq(x)` returns `false`. `null.eq(null)` returns `true`. When overriding the `equals` or `hashCode` methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (`o1 eq o2`), they should be equal to each other (`o1 == o2`) and they should hash to the same value (`o1.hashCode == o2.hashCode`). param `arg0` - the object to compare against this object for reference equality. return - `true` if the argument is a reference to the receiver object; `false` otherwise.	Boolean	AnyRef
equals	`def equals(arg0 : Any)` This method is used to compare the receiver object (`this`) with the argument object (`arg0`) for equivalence [details] The default implementations of this method is an equivalence relation: It is reflexive: for any instance `x` of type `Any`, `x.equals(x)` should return `true`. It is symmetric: for any instances `x` and `y` of type `Any`, `x.equals(y)` should return `true` if and only if `y.equals(x)` returns `true`. It is transitive: for any instances `x`, `y`, and `z` of type `AnyRef` if `x.equals(y)` returns `true` and `y.equals(z)` returns `true`, then `x.equals(z)` should return `true`. If you override this method, you should verify that your implementation remains an equivalence relation. Additionally, when overriding this method it is often necessary to override `hashCode` to ensure that objects that are "equal" (`o1.equals(o2)` returns `true`) hash to the same `Int` (`o1.hashCode.equals(o2.hashCode)`). param `arg0` - the object to compare against this object for equality. return - `true` if the receiver object is equivalent to the argument; `false` otherwise.	Boolean	AnyRef
filter	`def filter(p : (A) => Boolean)` If the option is nonempty and the given predicate `p` yields `false` on its value, return `None` [details] Otherwise return the option value itself. param `p` - the predicate used for testing.	Option[A]
finalize	`protected def finalize` This method is called by the garbage collector on the receiver object when garbage collection determines that there are no more references to the object [details] The details of when and if the `finalize` method are invoked, as well as the interaction between `finalize` and non-local returns and exceptions, are all platform dependent.	Unit	AnyRef
flatMap	`def flatMap[B](f : (A) => Option[B])` If the option is nonempty, return a function applied to its value [details] Otherwise return None. param `f` - the function to apply	Option[B]
foreach	`def foreach(f : (A) => Unit)` Apply the given procedure `f` to the option's value, if it is nonempty [details] Do nothing if it is empty. param `f` - the procedure to apply.	Unit
get	`def get[B >: A](default : B)` [details] deprecated - ; use `getOrElse` instead	B
getClass	`final def getClass` Returns a representation that corresponds to the dynamic class of the receiver object [details] The nature of the representation is platform dependent. return - a representation that corresponds to the dynamic class of the receiver object.	Class[Any]	AnyRef
getOrElse	`def getOrElse[B >: A](default : => B)` If the option is nonempty return its value, otherwise return the result of evaluating a default expression [details] param `default` - the default expression.	B
hashCode	`def hashCode` Returns a hash code value for the object [details] The default hashing algorithm is platform dependent. Note that it is allowed for two objects to have identical hash codes (`o1.hashCode.equals(o2.hashCode)`) yet not be equal (`o1.equals(o2)` returns `false`). A degenerate implementation could always return `0`. However, it is required that if two objects are equal (`o1.equals(o2)` returns `true`) that they have identical hash codes (`o1.hashCode.equals(o2.hashCode)`). Therefore, when overriding this method, be sure to verify that the behavior is consistent with the `equals` method. return - the hash code value for the object.	Int	AnyRef
isInstanceOf	`final def isInstanceOf[T0]` This method is used to test whether the dynamic type of the receiver object is `T0` [details] Note that the test result of the test is modulo Scala's erasure semantics. Therefore the expression `1.isInstanceOf[String]` will return `false`, while the expression `List(1).isInstanceOf[List[String]]` will return `true`. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested typed. return - `true` if the receiver object is an instance of erasure of type `T0`; `false` otherwise.	Boolean	Any
map	`def map[B](f : (A) => B)` If the option is nonempty, return a function applied to its value, wrapped in a Some i [details] e. `Some(f(this.get))`. Otherwise return `None`. param `f` - the function to apply	Option[B]
ne	`final def ne(arg0 : Object)` `o [details]` `ne(arg0)` is the same as `!(o.eq(arg0))`. param `arg0` - the object to compare against this object for reference dis-equality. return - `false` if the argument is not a reference to the receiver object; `true` otherwise.	Boolean	AnyRef
notify	`final def notify` Wakes up a single thread that is waiting on the receiver object's monitor	Unit	AnyRef
notifyAll	`final def notifyAll` Wakes up all threads that are waiting on the receiver object's monitor	Unit	AnyRef
orElse	`def orElse[B >: A](alternative : => Option[B])` If the option is nonempty return it, otherwise return the result of evaluating an alternative expression [details] param `alternative` - the alternative expression.	Option[B]
productElement	`abstract def productElement(n : Int)` for a product `A(x_1, [details]` `..,x_k)`, returns `x_(n+1)` for `0 <= n < k` param `n` - the index of the element to return return - The element `n` elements after the first element	Any	Product
synchronized	`final def synchronized[T0](arg0 : T0)`	T0	AnyRef
toLeft	`def toLeft[X](right : => X)` An `Either` that is a `Right` with the given argument `right` if this is empty, or a `Left` if this is nonempty with the option's value	Either[A, X] `with` Product
toRight	`def toRight[X](left : => X)` An `Either` that is a `Left` with the given argument `left` if this is empty, or a `Right` if this is nonempty with the option's value	Either[X, A] `with` Product
toString	`def toString` Returns a string representation of the object [details] The default representation is platform dependent. return - a string representation of the object.	String	AnyRef
wait	`final def wait`	Unit	AnyRef
wait	`final def wait(arg0 : Long)`	Unit	AnyRef
wait	`final def wait(arg0 : Long, arg1 : Int)`	Unit	AnyRef

scala.Option class Option

Direct Known Subclasses

Constructors

Fields

Methods

scala.Option

class Option