Packages

trait ClassTag[T] extends ClassManifestDeprecatedApis[T] with Equals with 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.

Annotations
@implicitNotFound( msg = "No ClassTag available for ${T}" )
Source
ClassTag.scala
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  1. ClassTag
  2. Equals
  3. ClassManifestDeprecatedApis
  4. OptManifest
  5. Serializable
  6. Serializable
  7. AnyRef
  8. Any
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  1. by any2stringadd
  2. by StringFormat
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Abstract Value Members

  1. abstract def runtimeClass: Class[_]

    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.

Concrete Value Members

  1. def canEqual(x: 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.

    returns

    true if this instance can possibly equal that, otherwise false

    Definition Classes
    ClassTagEqualsClassManifestDeprecatedApis
  2. def equals(x: Any): Boolean

    The universal equality method defined in AnyRef.

    The universal equality method defined in AnyRef.

    Definition Classes
    ClassTagEquals → AnyRef → Any
  3. def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in scala.Any.

    returns

    the hash code value for this object.

    Definition Classes
    ClassTag → AnyRef → Any
  4. 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

    Definition Classes
    ClassTagClassManifestDeprecatedApis
  5. def toString(): String

    Creates a String representation of this object.

    Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

    returns

    a String representation of the object.

    Definition Classes
    ClassTag → AnyRef → Any
  6. 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].

  7. def wrap: ClassTag[Array[T]]

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

Deprecated Value Members

  1. def <:<(that: ClassManifest[_]): 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.

    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) use scala.reflect.runtime.universe.TypeTag for subtype checking instead

  2. def >:>(that: ClassManifest[_]): 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.

    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) use scala.reflect.runtime.universe.TypeTag for subtype checking instead

  3. def arrayManifest: ClassManifest[Array[T]]
    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) use wrap instead

  4. def erasure: Class[_]
    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) use runtimeClass instead

  5. def newArray2(len: Int): Array[Array[T]]
    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) use wrap.newArray instead

  6. def newArray3(len: Int): Array[Array[Array[T]]]
    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) use wrap.wrap.newArray instead

  7. def newArray4(len: Int): Array[Array[Array[Array[T]]]]
    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) use wrap.wrap.wrap.newArray instead

  8. def newArray5(len: Int): Array[Array[Array[Array[Array[T]]]]]
    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) use wrap.wrap.wrap.wrap.newArray instead

  9. def newArrayBuilder(): ArrayBuilder[T]
    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) use ArrayBuilder.make(this) instead

  10. def newWrappedArray(len: Int): WrappedArray[T]
    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) create WrappedArray directly instead

  11. def typeArguments: List[OptManifest[_]]
    Definition Classes
    ClassManifestDeprecatedApis
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) use scala.reflect.runtime.universe.TypeTag to capture type structure instead