scala.reflect

ClassTag

trait ClassTag[T] extends ArrayTag[T] with ErasureTag[T] with Equals with Serializable

A ClassTag[T] wraps a Java class, which can be accessed via the erasure method.

This is useful in itself, but also enables very important use case. Having this knowledge ClassTag can instantiate Arrays in those cases where the element type is unknown at compile time. Hence, ClassTag[T] conforms to the ArrayTag[T] trait.

If an implicit value of type u.ClassTag[T] is required, the compiler will make one up on demand. The implicitly created value contains in its erasure field the Java class that is the result of erasing type T. In that value, any occurrences of type parameters or abstract types U which come themselves with a ClassTag or a reflect.mirror.ConcreteTypeTag are represented by the type referenced by that tag. If the type T contains unresolved references to type parameters or abstract types, a static error results.

A ConcreteTypeTag member of the reflect.mirror object is convertible to a ClassTag via an implicit conversion (this is not possible to do in all reflection universes because an operation that converts a type to a Java class might not be available).

Annotations
@implicitNotFound( msg = "No ClassTag available for ${T}" )
Source
ClassTag.scala
See also

TypeTags

Linear Supertypes
Serializable, Serializable, Equals, ErasureTag[T], ArrayTag[T], AnyRef, Any
Known Subclasses
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Inherited
  1. ClassTag
  2. Serializable
  3. Serializable
  4. Equals
  5. ErasureTag
  6. ArrayTag
  7. AnyRef
  8. Any
Implicitly
  1. by any2stringadd
  2. by any2stringfmt
  3. by any2ArrowAssoc
  4. by any2Ensuring
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Visibility
  1. Public
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Abstract Value Members

  1. abstract def erasure: Class[_]

    Returns an erasure of type T

    Returns an erasure of type T

    Definition Classes
    ErasureTag

Concrete Value Members

  1. final def !=(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  2. final def !=(arg0: Any): Boolean

    Test two objects for inequality.

    Test two objects for inequality.

    returns

    true if !(this == that), false otherwise.

    Definition Classes
    Any
  3. final def ##(): Int

    Equivalent to x.hashCode except for boxed numeric types and null.

    Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.

    returns

    a hash value consistent with ==

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

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to StringAdd performed by method any2stringadd in scala.Predef.
    Definition Classes
    StringAdd
  5. 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 any2ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  6. final def ==(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  7. final def ==(arg0: Any): Boolean

    Test two objects for equality.

    Test two objects for equality. The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    Any
  8. final def asInstanceOf[T0]: T0

    Cast the receiver object to be of type T0.

    Cast the receiver object to be of type T0.

    Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

    returns

    the receiver object.

    Definition Classes
    Any
    Exceptions thrown
    ClassCastException

    if the receiver object is not an instance of the erasure of type T0.

  9. def canEqual(x: Any): Boolean

    case class accessories

    case class accessories

    returns

    true if this instance can possibly equal that, otherwise false

    Definition Classes
    ClassTagEquals
  10. def clone(): AnyRef

    Create a copy of the receiver object.

    Create a copy of the receiver object.

    The default implementation of the clone method is platform dependent.

    returns

    a copy of the receiver object.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
    Note

    not specified by SLS as a member of AnyRef

  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 any2Ensuring 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 any2Ensuring 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 any2Ensuring 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 any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  15. final def eq(arg0: AnyRef): Boolean

    Tests whether the argument (arg0) is a reference to the receiver object (this).

    Tests whether the argument (arg0) is a reference to the receiver object (this).

    The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

    • It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
    • For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
    • null.eq(null) returns true.

    When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

    returns

    true if the argument is a reference to the receiver object; false otherwise.

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

    The universal equality method defined in AnyRef.

    The universal equality method defined in AnyRef.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

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

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

    The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
    Note

    not specified by SLS as a member of AnyRef

  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 performed by method any2stringfmt in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  19. final def getClass(): Class[_]

    A representation that corresponds to the dynamic class of the receiver object.

    A representation that corresponds to the dynamic class of the receiver object.

    The nature of the representation is platform dependent.

    returns

    a representation that corresponds to the dynamic class of the receiver object.

    Definition Classes
    AnyRef → Any
    Note

    not specified by SLS as a member of AnyRef

  20. def hashCode(): Int

    The hashCode method for reference types.

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

    returns

    the hash code value for this object.

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

    Test whether the dynamic type of the receiver object is T0.

    Test whether the dynamic type of the receiver object is T0.

    Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

    returns

    true if the receiver object is an instance of erasure of type T0; false otherwise.

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

    Equivalent to !(this eq that).

    Equivalent to !(this eq that).

    returns

    true if the argument is not a reference to the receiver object; false otherwise.

    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
    ClassTagArrayTag
  24. final def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Note

    not specified by SLS as a member of AnyRef

  25. final def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

    Wakes up all threads that are waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Note

    not specified by SLS as a member of AnyRef

  26. val self: Any

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to StringAdd performed by method any2stringadd in scala.Predef.
    Definition Classes
    StringAdd
  27. val self: Any

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to StringFormat performed by method any2stringfmt in scala.Predef.
    Definition Classes
    StringFormat
  28. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef
  29. 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
  30. final def wait(): Unit

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

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

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

    Produces a ClassTag that knows how to build Array[Array[T]]

    Produces a ClassTag that knows how to build Array[Array[T]]

    Definition Classes
    ClassTagArrayTag
  34. 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 any2ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Deprecated Value Members

  1. def x: ClassTag[T]

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to ArrowAssoc[ClassTag[T]] performed by method any2ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) Use leftOfArrow instead

  2. def x: ClassTag[T]

    Implicit information
    This member is added by an implicit conversion from ClassTag[T] to Ensuring[ClassTag[T]] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) Use resultOfEnsuring instead

Inherited from Serializable

Inherited from Serializable

Inherited from Equals

Inherited from ErasureTag[T]

Inherited from ArrayTag[T]

Inherited from AnyRef

Inherited from Any

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

Inherited by implicit conversion any2stringfmt from ClassTag[T] to StringFormat

Inherited by implicit conversion any2ArrowAssoc from ClassTag[T] to ArrowAssoc[ClassTag[T]]

Inherited by implicit conversion any2Ensuring from ClassTag[T] to Ensuring[ClassTag[T]]