scala

# None

#### object None extends Option[Nothing] with Product with Serializable

This case object represents non-existent values.

Source
  Option.scala
Version

  1.0, 16/07/2003

Linear Supertypes
Option[Nothing], Serializable, Serializable, Product, Equals, AnyRef, Any
Ordering

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Inherited

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1. None
2. Option
3. Serializable
4. Serializable
5. Product
6. Equals
7. AnyRef
8. Any

Visibility

1. Public
2. All

### 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. #### final def !=(arg0: AnyRef): Boolean

   Definition Classes
     AnyRef

2. #### final def !=(arg0: Any): Boolean

   Test two objects for inequality.

   Test two objects for inequality.

   returns

     `true` if !(this == that), false otherwise.

   Definition Classes
     Any

3. #### final def ##(): Int

   Equivalent to `x.hashCode` except for boxed numeric types and `null`.

   Equivalent to `x.hashCode` except for boxed numeric types and `null`. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For `null` returns a hashcode where `null.hashCode` throws a `NullPointerException`.

   returns

     a hash value consistent with ==

   Definition Classes
     AnyRef → Any

4. #### final def ==(arg0: AnyRef): Boolean

   Definition Classes
     AnyRef

5. #### final def ==(arg0: Any): Boolean

   Test two objects for equality.

   Test two objects for equality. The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

   returns

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

   Definition Classes
     Any

6. #### final def asInstanceOf[T0]: T0

   Cast the receiver object to be of type `T0`.

   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 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 type.

   returns

     the receiver object.

   Definition Classes
     Any
   Exceptions thrown
     ClassCastException

     if the receiver object is not an instance of the erasure of type `T0`.

7. #### def clone(): AnyRef

   Create a copy of the receiver object.

   Create 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[lang]
   Definition Classes
     AnyRef
   Annotations
     @throws()
   Note

     not specified by SLS as a member of AnyRef

8. #### def collect[B](pf: PartialFunction[Nothing, B]): Option[B]

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

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

   pf

     the partial function.

   returns

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

   Definition Classes
     Option

9. #### final def eq(arg0: AnyRef): Boolean

   Tests whether the argument (`arg0`) is a reference to the receiver object (`this`).

   Tests whether the argument (`arg0`) is a reference to the receiver object (`this`).

   The `eq` method implements an equivalence relation on non-null instances of `AnyRef`, and has three additional 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`).

   returns

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

   Definition Classes
     AnyRef

10. #### def equals(arg0: Any): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to `eq`.

    See also `equals` in Any.

    returns

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

    Definition Classes
      AnyRef → Any

11. #### final def exists(p: (Nothing) ⇒ Boolean): Boolean

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

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

    p

      the predicate to test

    Definition Classes
      Option
    Annotations
      @inline()

12. #### final def filter(p: (Nothing) ⇒ Boolean): Option[Nothing]

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

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

    p

      the predicate used for testing.

    Definition Classes
      Option
    Annotations
      @inline()

13. #### final def filterNot(p: (Nothing) ⇒ Boolean): Option[Nothing]

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

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

    p

      the predicate used for testing.

    Definition Classes
      Option
    Annotations
      @inline()

14. #### def finalize(): Unit

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

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

    Attributes
      protected[lang]
    Definition Classes
      AnyRef
    Annotations
      @throws()
    Note

      not specified by SLS as a member of AnyRef

15. #### final def flatMap[B](f: (Nothing) ⇒ Option[B]): Option[B]

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

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

    f

      the function to apply

    Definition Classes
      Option
    Annotations
      @inline()
    See also

      foreach

      ,

      map

16. #### def flatten[B](implicit ev: <:<[Nothing, Option[B]]): Option[B]

    Definition Classes
      Option

17. #### final def forall(p: (Nothing) ⇒ Boolean): Boolean

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

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

    p

      the predicate to test

    Definition Classes
      Option
    Annotations
      @inline()

18. #### 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.

    f

      the procedure to apply.

    Definition Classes
      Option
    Annotations
      @inline()
    See also

      flatMap

      ,

      map

19. #### def get: Nothing

    Returns the option's value.

    Returns the option's value.

    Definition Classes
      None → Option
    Exceptions thrown
      Predef.NoSuchElementException

      if the option is empty.

    Note

      The option must be nonEmpty.

20. #### final def getClass(): Class[_]

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

    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.

    Definition Classes
      AnyRef → Any
    Note

      not specified by SLS as a member of AnyRef

21. #### final def getOrElse[B >: Nothing](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`.

    default

      the default expression.

    Definition Classes
      Option
    Annotations
      @inline()

22. #### def isDefined: Boolean

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

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

    Definition Classes
      Option

23. #### def isEmpty: Boolean

    Returns true if the option is `None`, false otherwise.

    Returns true if the option is `None`, false otherwise.

    Definition Classes
      None → Option

24. #### final def isInstanceOf[T0]: Boolean

    Test whether the dynamic type of the receiver object is `T0`.

    Test whether the dynamic type of the receiver object is `T0`.

    Note that the 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 specified type.

    returns

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

    Definition Classes
      Any

25. #### def iterator: Iterator[Nothing]

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

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

    Definition Classes
      Option

26. #### final def map[B](f: (Nothing) ⇒ B): Option[B]

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

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

    f

      the function to apply

    Definition Classes
      Option
    Annotations
      @inline()
    Note

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

    See also

      foreach

      ,

      flatMap

27. #### final def ne(arg0: AnyRef): Boolean

    Equivalent to `!(this eq that)`.

    Equivalent to `!(this eq that)`.

    returns

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

    Definition Classes
      AnyRef

28. #### final def nonEmpty: Boolean

    Returns false if the option is `None`, true otherwise.

    Returns false if the option is `None`, true otherwise.

    Definition Classes
      Option
    Note

      Implemented here to avoid the implicit conversion to Iterable.

29. #### final 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.

    Definition Classes
      AnyRef
    Note

      not specified by SLS as a member of AnyRef

30. #### final 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.

    Definition Classes
      AnyRef
    Note

      not specified by SLS as a member of AnyRef

31. #### final def orElse[B >: Nothing](alternative: ⇒ Option[B]): Option[B]

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

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

    alternative

      the alternative expression.

    Definition Classes
      Option
    Annotations
      @inline()

32. #### final def orNull[A1 >: Nothing](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 Option must often interface with code that expects and returns nulls.

    Definition Classes
      Option
    Annotations
      @inline()
    Example:

    1.     val initalText: Option[String] = getInitialText
           val textField = new JComponent(initalText.orNull,20)

33. #### final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
      AnyRef

34. #### final def toLeft[X](right: ⇒ X): Product with Serializable with Either[Nothing, X]

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

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

    right

      the expression to evaluate and return if this is empty

    Definition Classes
      Option
    Annotations
      @inline()
    See also

      toRight

35. #### def toList: List[Nothing]

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

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

    Definition Classes
      Option

36. #### final def toRight[X](left: ⇒ X): Product with Serializable with Either[X, Nothing]

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

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

    left

      the expression to evaluate and return if this is empty

    Definition Classes
      Option
    Annotations
      @inline()
    See also

      toLeft

37. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws()

38. #### final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws()

39. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws()

40. #### def withFilter(p: (Nothing) ⇒ 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.

    Definition Classes
      Option

### Inherited from Option[Nothing]

### Inherited from Serializable

### Inherited from Product

### Inherited from Equals

### Inherited from AnyRef

### Inherited from Any