scala.reflect

Manifest

trait Manifest[T] extends ClassManifest[T] with Equals

A Manifest[T] is an opaque descriptor for type T. Its supported use is to give access to the erasure of the type as a Class instance, as is necessary for the creation of native Arrays if the class is not known at compile time.

The type-relation operators <:< and =:= should be considered approximations only, as there are numerous aspects of type conformance which are not yet adequately represented in manifests.

Example usages:

  def arr[T] = new Array[T](0)                          // does not compile
  def arr[T](implicit m: Manifest[T]) = new Array[T](0) // compiles
  def arr[T: Manifest] = new Array[T](0)                // shorthand for the preceding

  // Methods manifest, classManifest, and optManifest are in [[scala.Predef]].
  def isApproxSubType[T: Manifest, U: Manifest] = manifest[T] <:< manifest[U]
  isApproxSubType[List[String], List[AnyRef]] // true
  isApproxSubType[List[String], List[Int]]    // false

  def methods[T: ClassManifest] = classManifest[T].erasure.getMethods
  def retType[T: ClassManifest](name: String) =
    methods[T] find (_.getName == name) map (_.getGenericReturnType)

  retType[Map[_, _]]("values")  // Some(scala.collection.Iterable)
Annotations
@implicitNotFound( msg = "No Manifest available for ${T}." )
Source
Manifest.scala
Linear Supertypes
ClassManifest[T], Equals, OptManifest[T], Serializable, Serializable, AnyRef, Any
Known Subclasses
Ordering
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Inherited
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  1. Manifest
  2. ClassManifest
  3. Equals
  4. OptManifest
  5. Serializable
  6. Serializable
  7. AnyRef
  8. Any
Visibility
  1. Public
  2. All

Abstract Value Members

  1. abstract def erasure: java.lang.Class[_]

    A class representing the type U to which T would be erased.

    A class representing the type U to which T would be erased. Note that there is no subtyping relationship between T and U.

    Definition Classes
    ClassManifest

Concrete 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.

    Equivalent to x.hashCode except for boxed numeric types. 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.

    returns

    a hash value consistent with ==

    Definition Classes
    AnyRef → Any
  4. def <:<(that: scala.reflect.ClassManifest[_]): Boolean

    Tests whether the type represented by this manifest is a subtype of the type represented by that' manifest, subject to the limitations described in the header.

    Tests whether the type represented by this manifest is a subtype of the type represented by that' manifest, subject to the limitations described in the header.

    Definition Classes
    ClassManifest
  5. final def ==(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  6. final def ==(arg0: Any): Boolean

    Test two objects for equality.

    Test two objects for equality.

    returns

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

    Definition Classes
    Any
  7. def >:>(that: scala.reflect.ClassManifest[_]): Boolean

    Tests whether the type represented by this manifest is a supertype of the type represented by that' manifest, subject to the limitations described in the header.

    Tests whether the type represented by this manifest is a supertype of the type represented by that' manifest, subject to the limitations described in the header.

    Definition Classes
    ClassManifest
  8. def argString: String

    Attributes
    protected
    Definition Classes
    ClassManifest
  9. def arrayClass[T](tp: java.lang.Class[_]): Class[Array[T]]

    Attributes
    protected
    Definition Classes
    ClassManifest
  10. def arrayManifest: Manifest[Array[T]]

    Definition Classes
    ManifestClassManifest
  11. 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.

  12. 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.

    that

    the value being probed for possible equality

    returns

    true if this instance can possibly equal that, otherwise false

    Definition Classes
    ManifestClassManifestEquals
  13. 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

  14. 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
  15. def equals(that: Any): Boolean

    Note: testing for erasure here is important, as it is many times faster than <:< and rules out most comparisons.

    Note: testing for erasure here is important, as it is many times faster than <:< and rules out most comparisons.

    that

    the object to compare against this object for equality.

    returns

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

    Definition Classes
    ManifestClassManifestEquals → AnyRef → Any
  16. 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

  17. final def getClass(): java.lang.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

  18. def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in Any.

    returns

    the hash code value for this object.

    Definition Classes
    ManifestClassManifest → AnyRef → Any
  19. 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
  20. 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
  21. def newArray(len: Int): Array[T]

    Definition Classes
    ClassManifest
  22. def newArray2(len: Int): Array[Array[T]]

    Definition Classes
    ClassManifest
  23. def newArray3(len: Int): Array[Array[Array[T]]]

    Definition Classes
    ClassManifest
  24. def newArray4(len: Int): Array[Array[Array[Array[T]]]]

    Definition Classes
    ClassManifest
  25. def newArray5(len: Int): Array[Array[Array[Array[Array[T]]]]]

    Definition Classes
    ClassManifest
  26. def newArrayBuilder(): ArrayBuilder[T]

    Definition Classes
    ClassManifest
  27. def newWrappedArray(len: Int): WrappedArray[T]

    Definition Classes
    ClassManifest
  28. 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

  29. 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

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

    Definition Classes
    AnyRef
  31. def toString(): String

    Creates a String representation of this object.

    Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

    returns

    a String representation of the object.

    Definition Classes
    AnyRef → Any
  32. def typeArguments: List[scala.reflect.Manifest[_]]

    Definition Classes
    ManifestClassManifest
  33. final def wait(): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()
  34. final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()
  35. final def wait(arg0: Long): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()

Inherited from ClassManifest[T]

Inherited from Equals

Inherited from OptManifest[T]

Inherited from Serializable

Inherited from Serializable

Inherited from AnyRef

Inherited from Any