ClassTag

scala.reflect.ClassTag

See theClassTag companion object

trait ClassTag[T] extends ClassManifestDeprecatedApis[T], Equals, Serializable

A ClassTag[T] stores the erased class of a given type T, accessible via the runtimeClass field. This is particularly useful for instantiating Arrays whose element types are unknown at compile time.

ClassTags are a weaker special case of scala.reflect.api.TypeTags.TypeTags, in that they wrap only the runtime class of a given type, whereas a TypeTag contains all static type information. That is, ClassTags are constructed from knowing only the top-level class of a type, without necessarily knowing all of its argument types. This runtime information is enough for runtime Array creation.

For example:

scala> def mkArray[T : ClassTag](elems: T*) = Array[T](elems: _*)
mkArray: [T](elems: T*)(implicit evidence$1: scala.reflect.ClassTag[T])Array[T]

scala> mkArray(42, 13)
res0: Array[Int] = Array(42, 13)

scala> mkArray("Japan","Brazil","Germany")
res1: Array[String] = Array(Japan, Brazil, Germany)

See scala.reflect.api.TypeTags for more examples, or the Reflection Guide: TypeTags for more details.

Attributes

Companion: object
Source: ClassTag.scala
Graph
Supertypes: trait Equals

trait ClassManifestDeprecatedApis[T]

trait OptManifest[T]

trait Serializable

class Object

trait Matchable

class Any
Show all
Known subtypes: trait Manifest[T]

class AnyValManifest[T]

Members list

Value members

Abstract methods

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

Source: ClassTag.scala

Concrete methods

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: Equals -> ClassManifestDeprecatedApis
Source: ClassTag.scala

The universal equality method defined in AnyRef.

Attributes

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

Produces a new array with element type T and length len

Attributes

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: Any
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

Source: ClassTag.scala

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

Attributes

Source: ClassTag.scala

Inherited methods

Attributes

Inherited from:: ClassManifestDeprecatedApis
Source: ClassManifestDeprecatedApis.scala

Attributes

Inherited from:: ClassManifestDeprecatedApis
Source: ClassManifestDeprecatedApis.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.