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.
- Companion:
- object
- Source:
- ClassTag.scala
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.
- 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
- Returns:
true if this instance can possibly equal
that, otherwise false- Definition Classes
- Source:
- ClassTag.scala
The universal equality method defined in AnyRef.
The universal equality method defined in AnyRef.
- Definition Classes
- Source:
- ClassTag.scala
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.
- Returns:
the hash code value for this object.
- Definition Classes
- Source:
- ClassTag.scala
Produces a new array with element type T and length len
Produces a new array with element type T and length len
- Source:
- ClassTag.scala
Returns a string representation of the object.
Returns a string representation of the object.
The default representation is platform dependent.
- Returns:
a string representation of the object.
- Definition Classes
- Source:
- ClassTag.scala
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].
- 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]]
- Source:
- ClassTag.scala
Inherited methods
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.
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.
- Deprecated
- 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.
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.
- Deprecated
- Inherited from:
- ClassManifestDeprecatedApis
- Source:
- ClassManifestDeprecatedApis.scala