scala

Option

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.

attributes: sealed abstract
go to: companion
linear super types: Product, Equals, AnyRef, Any
known subclasses: None, Some
self type: Option[A]
source: Option.scala
    version
  1. 1.1, 16/01/2007

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  1. Option
  2. Product
  3. Equals
  4. AnyRef
  5. Any
Visibility
  1. Public
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Impl.
  1. Concrete
  2. Abstract

Instance constructors

  1. new Option ()

Type Members

  1. class WithFilter extends AnyRef

    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.

Value Members

  1. def != (arg0: AnyRef) : Boolean

    attributes: final
    definition classes: AnyRef
  2. def != (arg0: Any) : Boolean

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

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

    arg0

    the object to compare against this object for dis-equality.

    returns

    false if the receiver object is equivalent to the argument; true otherwise.

    attributes: final
    definition classes: Any
  3. def ## () : Int

    attributes: final
    definition classes: AnyRef → Any
  4. def $asInstanceOf [T0] () : T0

    attributes: final
    definition classes: AnyRef
  5. def $isInstanceOf [T0] () : Boolean

    attributes: final
    definition classes: AnyRef
  6. def == (arg0: AnyRef) : Boolean

    o == arg0 is the same as if (o eq null) arg0 eq null else o.equals(arg0).

    o == arg0 is the same as if (o eq null) arg0 eq null else o.equals(arg0).

    arg0

    the object to compare against this object for equality.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    attributes: final
    definition classes: AnyRef
  7. def == (arg0: Any) : Boolean

    o == arg0 is the same as o.equals(arg0).

    o == arg0 is the same as o.equals(arg0).

    arg0

    the object to compare against this object for equality.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    attributes: final
    definition classes: Any
  8. def asInstanceOf [T0] : T0

    This method is used to cast the receiver object to be of type T0.

    This method is used to cast the receiver object to be of type T0.

    Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expressionList(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.

    returns

    the receiver object.

    attributes: final
    definition classes: Any
  9. def canEqual (that: Any) : Boolean

    A method that should be called from every well-designed equals method that is open to be overridden in a subclass.

    A method that should be called from every well-designed equals method that is open to be overridden in a subclass. See Programming in Scala, Chapter 28 for discussion and design.

    attributes: abstract
    definition classes: Equals
  10. def clone () : AnyRef

    This method creates and returns a copy of the receiver object.

    This method creates and returns a copy of the receiver object.

    The default implementation of the clone method is platform dependent.

    returns

    a copy of the receiver object.

    attributes: protected
    definition classes: AnyRef
  11. def collect [B] (pf: PartialFunction[A, B]) : Option[B]

    If the given partial function pf is defined for the option's value, apply it to the value.

    If the given partial function pf is defined for the option's value, apply it to the value. Otherwise, None.

    pf

    the partial function.

  12. def eq (arg0: AnyRef) : Boolean

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

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

    The eq method implements an [http://en.wikipedia.org/wiki/Equivalence_relation 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).

    arg0

    the object to compare against this object for reference equality.

    returns

    true if the argument is a reference to the receiver object; false otherwise.

    attributes: final
    definition classes: AnyRef
  13. def equals (arg0: Any) : Boolean

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

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

    The default implementations of this method is an [http://en.wikipedia.org/wiki/Equivalence_relation 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 scala.Int (o1.hashCode.equals(o2.hashCode)).

    arg0

    the object to compare against this object for equality.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    definition classes: AnyRef → Any
  14. def exists (p: (A) ⇒ Boolean) : Boolean

    If the option is nonempty, p(value), otherwise false.

    If the option is nonempty, p(value), otherwise false.

    p

    the predicate to test

  15. def filter (p: (A) ⇒ Boolean) : Option[A]

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

    If the option is nonempty and the given predicate p yields false on its value, return None. Otherwise return the option value itself.

    p

    the predicate used for testing.

  16. def finalize () : Unit

    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.

    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.

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

    attributes: protected
    definition classes: AnyRef
  17. def flatMap [B] (f: (A) ⇒ Option[B]) : Option[B]

    If the option is nonempty, return a function applied to its value.

    If the option is nonempty, return a function applied to its value. Otherwise return None.

    f

    the function to apply

  18. def foreach [U] (f: (A) ⇒ 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. Do nothing if it is empty.

    f

    the procedure to apply.

  19. def get : A

    get the value of this option.

    get the value of this option.

    attributes: abstract
  20. def getClass () : java.lang.Class[_]

    Returns a representation that corresponds to the dynamic class of the receiver object.

    Returns a representation that corresponds to the dynamic class of the receiver object.

    The nature of the representation is platform dependent.

    returns

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

    attributes: final
    definition classes: AnyRef
  21. def getOrElse [B >: A] (default: ⇒ B) : B

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

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

    default

    the default expression.

  22. def hashCode () : Int

    Returns a hash code value for the object.

    Returns a hash code value for the object.

    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.

    returns

    the hash code value for the object.

    definition classes: AnyRef → Any
  23. def isDefined : Boolean

    True if the option is a Some(.

    True if the option is a Some(...) false otherwise.

  24. def isEmpty : Boolean

    True if the option is the None value, false otherwise.

    True if the option is the None value, false otherwise.

    attributes: abstract
  25. def isInstanceOf [T0] : Boolean

    This method is used to test whether the dynamic type of the receiver object is T0.

    This method is used to test whether the dynamic type of the receiver object is T0.

    Note that the test result of the test is modulo Scala's erasure semantics. Therefore the expression1.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.

    returns

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

    attributes: final
    definition classes: Any
  26. def iterator : Iterator[A]

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

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

  27. 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.

    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.

    f

    the function to apply

  28. def ne (arg0: AnyRef) : Boolean

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

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

    arg0

    the object to compare against this object for reference dis-equality.

    returns

    false if the argument is not a reference to the receiver object; true otherwise.

    attributes: final
    definition classes: AnyRef
  29. def notify () : Unit

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

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

    attributes: final
    definition classes: AnyRef
  30. def notifyAll () : Unit

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

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

    attributes: final
    definition classes: AnyRef
  31. 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.

    If the option is nonempty return it, otherwise return the result of evaluating an alternative expression.

    alternative

    the alternative expression.

  32. def orNull [A1 >: A] (implicit ev: <:<[Null, A1]) : A1

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

    The option's value if it is nonempty, or null if it is empty. The use of null of course is discouraged, but code written to use Options often must interface with code which expects and returns nulls.

  33. def productArity : Int

    return k for a product A(x_1,...,x_k)

    return k for a product A(x_1,...,x_k)

    attributes: abstract
    definition classes: Product
  34. def productElement (n: Int) : Any

    For a product A(x_1,...,x_k), returns x_(n+1) for 0 <= n < k

    For a product A(x_1,...,x_k), returns x_(n+1) for 0 <= n < k

    n

    the index of the element to return

    returns

    The element n elements after the first element

    attributes: abstract
    definition classes: Product
  35. def productElements : Iterator[Any]

    definition classes: Product
      deprecated:
    1. use productIterator instead

  36. def productIterator : Iterator[Any]

    An iterator that returns all fields of this product

    An iterator that returns all fields of this product

    definition classes: Product
  37. def productPrefix : String

    By default the empty string.

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

    definition classes: Product
  38. def synchronized [T0] (arg0: T0) : T0

    attributes: final
    definition classes: AnyRef
  39. def toLeft [X] (right: ⇒ X) : Product with Either[A, X]

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

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

  40. 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.

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

  41. def toRight [X] (left: ⇒ X) : Product with Either[X, A]

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

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

  42. def toString () : String

    Returns a string representation of the object.

    Returns a string representation of the object.

    The default representation is platform dependent.

    returns

    a string representation of the object.

    definition classes: AnyRef → Any
  43. def wait () : Unit

    attributes: final
    definition classes: AnyRef
  44. def wait (arg0: Long, arg1: Int) : Unit

    attributes: final
    definition classes: AnyRef
  45. def wait (arg0: Long) : Unit

    attributes: final
    definition classes: AnyRef
  46. def withFilter (p: (A) ⇒ Boolean) : WithFilter

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

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

Inherited from Product

Inherited from Equals

Inherited from AnyRef

Inherited from Any