scala.reflect

ClassTag

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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Inherited
  1. ClassTag
  2. Equals
  3. ClassManifestDeprecatedApis
  4. OptManifest
  5. Serializable
  6. Serializable
  7. AnyRef
  8. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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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. final def !=(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any
  2. final def ##(): Int

    Definition Classes
    AnyRef → Any
  3. def +(other: String): String

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to any2stringadd[ClassTag[T]] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. def ->[B](y: B): (ClassTag[T], B)

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to ArrowAssoc[ClassTag[T]] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  5. final def ==(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any
  6. def argString: String

    Attributes
    protected
    Definition Classes
    ClassManifestDeprecatedApis
  7. def arrayClass[T](tp: Class[_]): Class[Array[T]]

    Attributes
    protected
    Definition Classes
    ClassManifestDeprecatedApis
  8. final def asInstanceOf[T0]: T0

    Definition Classes
    Any
  9. 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
  10. def clone(): AnyRef

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  11. def ensuring(cond: (ClassTag[T]) ⇒ Boolean, msg: ⇒ Any): ClassTag[T]

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to Ensuring[ClassTag[T]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  12. def ensuring(cond: (ClassTag[T]) ⇒ Boolean): ClassTag[T]

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to Ensuring[ClassTag[T]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  13. def ensuring(cond: Boolean, msg: ⇒ Any): ClassTag[T]

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to Ensuring[ClassTag[T]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  14. def ensuring(cond: Boolean): ClassTag[T]

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to Ensuring[ClassTag[T]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  15. final def eq(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  16. def equals(x: Any): Boolean

    The universal equality method defined in AnyRef.

    The universal equality method defined in AnyRef.

    Definition Classes
    ClassTagEquals → AnyRef → Any
  17. def finalize(): Unit

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  18. def formatted(fmtstr: String): String

    Returns string formatted according to given format string.

    Returns string formatted according to given format string. Format strings are as for String.format (@see java.lang.String.format).

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to StringFormat[ClassTag[T]] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  19. final def getClass(): Class[_]

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

    Definition Classes
    ClassTag → AnyRef → Any
  21. final def isInstanceOf[T0]: Boolean

    Definition Classes
    Any
  22. final def ne(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  23. 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
  24. final def notify(): Unit

    Definition Classes
    AnyRef
  25. final def notifyAll(): Unit

    Definition Classes
    AnyRef
  26. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef
  27. def toString(): String

    Definition Classes
    ClassTag → AnyRef → Any
  28. def unapply(x: Unit): Option[T]

  29. def unapply(x: Boolean): Option[T]

  30. def unapply(x: Double): Option[T]

  31. def unapply(x: Float): Option[T]

  32. def unapply(x: Long): Option[T]

  33. def unapply(x: Int): Option[T]

  34. def unapply(x: Char): Option[T]

  35. def unapply(x: Short): Option[T]

  36. def unapply(x: Byte): Option[T]

  37. 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].

  38. final def wait(): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  39. final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  40. final def wait(arg0: Long): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  41. def wrap: ClassTag[Array[T]]

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

  42. def [B](y: B): (ClassTag[T], B)

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to ArrowAssoc[ClassTag[T]] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

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

Inherited from Equals

Inherited from ClassManifestDeprecatedApis[T]

Inherited from OptManifest[T]

Inherited from Serializable

Inherited from java.io.Serializable

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from ClassTag[T] to any2stringadd[ClassTag[T]]

Inherited by implicit conversion StringFormat from ClassTag[T] to StringFormat[ClassTag[T]]

Inherited by implicit conversion Ensuring from ClassTag[T] to Ensuring[ClassTag[T]]

Inherited by implicit conversion ArrowAssoc from ClassTag[T] to ArrowAssoc[ClassTag[T]]

Ungrouped