Manifest

scala.reflect.Manifest

See theManifest companion object

trait Manifest[T] extends ClassTag[T], 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 ClassManifestDeprecatedApis[T]

trait OptManifest[T]

trait Serializable

class Object

trait Matchable

class Any
Show all
Known subtypes: class AnyValManifest[T]

Members list

Value members

Concrete methods

Attributes

Definition Classes: ClassManifestDeprecatedApis
Source: Manifest.scala

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.

Value parameters

that: the value being probed for possible equality

Attributes

Returns: true if this instance can possibly equal that, otherwise false
Definition Classes: ClassTag -> Equals -> ClassManifestDeprecatedApis
Source: Manifest.scala

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

Attributes

Definition Classes: ClassTag -> Equals -> Any
Source: Manifest.scala

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: ClassTag -> Any
Source: Manifest.scala

Attributes

Definition Classes: ClassManifestDeprecatedApis
Source: Manifest.scala

Inherited methods

Attributes

Inherited from:: ClassManifestDeprecatedApis
Source: ClassManifestDeprecatedApis.scala

Attributes

Inherited from:: ClassManifestDeprecatedApis
Source: ClassManifestDeprecatedApis.scala

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

Returns a string representation of the object.

The default representation is platform dependent.

Attributes

Returns: a string representation of the object.
Definition Classes: ClassTag -> Any
Inherited from:: ClassTag
Source: ClassTag.scala

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]]

Attributes

Inherited from:: ClassTag
Source: ClassTag.scala

Deprecated and Inherited methods

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

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.