Manifest

scala.reflect.Manifest
See theManifest companion object
trait Manifest[T] extends ClassTag[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 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: Manifest] = manifest[T].runtimeClass.getMethods
def retType[T: Manifest](name: String) =
  methods[T] find (_.getName == name) map (_.getGenericReturnType)

retType[Map[_, _]]("values")  // Some(scala.collection.Iterable<B>)

Attributes

Companion:
object
Source:
Manifest.scala
Graph
Supertypes
trait ClassTag[T]
trait Equals
trait OptManifest[T]
class Object
trait Matchable
class Any
Known subtypes

Members list

Concise view

Value members

Concrete methods

override def arrayManifest: Manifest[Array[T]]

Attributes

Definition Classes
Source:
Manifest.scala
override 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

that

the value being probed for possible equality

Returns:

true if this instance can possibly equal that, otherwise false

Definition Classes
Source:
Manifest.scala
override 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.

Attributes

Definition Classes
Source:
Manifest.scala
override def hashCode: Int

Calculate a hash code value for the object.

Calculate 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.

Attributes

Returns:

the hash code value for this object.

Definition Classes
Source:
Manifest.scala
override def typeArguments: List[Manifest[_]]

Attributes

Definition Classes
Source:
Manifest.scala

Inherited methods

protected def arrayClass[A](tp: Class[_]): Class[Array[A]]
def newArray(len: Int): Array[T]

Produces a new array with element type T and length len

Produces a new array with element type T and length len

Attributes

Inherited from:
ClassTag
Source:
ClassTag.scala

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.

Attributes

Inherited from:
ClassTag
Source:
ClassTag.scala
override def toString: String

Returns a string representation of the object.

Returns a string representation of the object.

The default representation is platform dependent.

Attributes

Returns:

a string representation of the object.

Definition Classes
Inherited from:
ClassTag
Source:
ClassTag.scala
def unapply(x: Any): Option[T]

A ClassTag[T] can serve as an extractor that matches only objects of type T.

A ClassTag[T] can serve as an extractor that matches only objects of type T.

The compiler tries to turn unchecked type tests in pattern matches into checked ones by wrapping a (_: T) type pattern as ct(_: T), where ct is the ClassTag[T] instance. Type tests necessary before calling other extractors are treated similarly. SomeExtractor(...) is turned into ct(SomeExtractor(...)) if T in SomeExtractor.unapply(x: T) is uncheckable, but we have an instance of ClassTag[T].

Attributes

Inherited from:
ClassTag
Source:
ClassTag.scala

Produces a ClassTag that knows how to instantiate an Array[Array[T]]

Produces a ClassTag that knows how to instantiate an Array[Array[T]]

Attributes

Inherited from:
ClassTag
Source:
ClassTag.scala

Deprecated and Inherited methods

def <:<(that: ClassTag[_]): 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.

Attributes

Deprecated
true
Inherited from:
ClassManifestDeprecatedApis
Source:
ClassManifestDeprecatedApis.scala
def >:>(that: ClassTag[_]): 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.

Attributes

Deprecated
true
Inherited from:
ClassManifestDeprecatedApis
Source:
ClassManifestDeprecatedApis.scala
def erasure: Class[_]

Attributes

Deprecated
true
Inherited from:
ClassManifestDeprecatedApis
Source:
ClassManifestDeprecatedApis.scala
def newArray2(len: Int): Array[Array[T]]

Attributes

Deprecated
true
Inherited from:
ClassManifestDeprecatedApis
Source:
ClassManifestDeprecatedApis.scala
def newArray3(len: Int): Array[Array[Array[T]]]

Attributes

Deprecated
true
Inherited from:
ClassManifestDeprecatedApis
Source:
ClassManifestDeprecatedApis.scala
def newArray4(len: Int): Array[Array[Array[Array[T]]]]

Attributes

Deprecated
true
Inherited from:
ClassManifestDeprecatedApis
Source:
ClassManifestDeprecatedApis.scala

Attributes

Deprecated
true
Inherited from:
ClassManifestDeprecatedApis
Source:
ClassManifestDeprecatedApis.scala

Attributes

Deprecated
true
Inherited from:
ClassManifestDeprecatedApis
Source:
ClassManifestDeprecatedApis.scala