ClassTag (original) (raw)
scala.reflect.ClassTag
See theClassTag companion object
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
Source
Graph
Supertypes
Known subtypes
Members list
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
Checks whether this instance can possibly equal that.
Checks whether this instance can possibly equal that.
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
Source
Checks whether this instance is equal to that.
Checks whether this instance is equal to that. This universal equality method is defined in AnyRef.
Attributes
Definition Classes
Source
Calculates a hash code value for the object.
Calculates 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
Produces a new array with element type T and length len
Produces a new array with element type T and length len
Attributes
Source
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
Source
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
Source
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
Source
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
[Since version 2.10.0] use scala.reflect.runtime.universe.TypeTag for subtype checking instead
Inherited from:
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.
Attributes
Deprecated
[Since version 2.10.0] use scala.reflect.runtime.universe.TypeTag for subtype checking instead
Inherited from:
Source
ClassManifestDeprecatedApis.scala
In this article