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 wrap only the runtime class of a given 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*)
def mkArray[T](elems: T*)(using ClassTag[T]): Array[T]
scala> mkArray(42, 13)
val res0: Array[Int] = Array(42, 13)
scala> mkArray("Japan","Brazil","Germany")
val res1: Array[String] = Array(Japan, Brazil, Germany)
For compile-time type information in macros, see the facilities in the scala.quoted package. For limited runtime type checks beyond what Class[?] provides, see scala.reflect.TypeTest and scala.reflect.Typeable.
Attributes
- Companion
- object
- Graph
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- Supertypes
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trait Equalstrait ClassManifestDeprecatedApis[T]trait OptManifest[T]trait Serializableclass Objecttrait Matchableclass AnyShow all
- Known subtypes
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trait Manifest[T]class AnyValManifest[T]
Members list
Value members
Abstract methods
A class representing the type U to which T would be erased. Note that there is no subtyping relationship between T and U.
A class representing the type U to which T would be erased. Note that there is no subtyping relationship between T and U.
Attributes
Concrete methods
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
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the value being probed for possible equality
Attributes
- Returns
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true if this instance can possibly equal
that, otherwise false - Definition Classes
Checks whether this instance is equal to that. This universal equality method is defined in AnyRef.
Checks whether this instance is equal to that. This universal equality method is defined in AnyRef.
Attributes
- Definition Classes
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Equals -> Any
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
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the hash code value for this object.
- Definition Classes
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Any
Produces a new array with element type T and length len.
Produces a new array with element type T and length len.
Attributes
Returns a string representation of the object.
Returns a string representation of the object.
The default representation is platform dependent.
Attributes
- Returns
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a string representation of the object.
- Definition Classes
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Any
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
Inherited methods
Attributes
- Inherited from:
- ClassManifestDeprecatedApis
Attributes
- Inherited from:
- ClassManifestDeprecatedApis
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.
Attributes
- Deprecated
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[Since version 2.10.0]use scala.reflect.runtime.universe.TypeTag for subtype checking instead - Inherited from:
- ClassManifestDeprecatedApis
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
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[Since version 2.10.0]use scala.reflect.runtime.universe.TypeTag for subtype checking instead - Inherited from:
- ClassManifestDeprecatedApis
Attributes
- Deprecated
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[Since version 2.10.0]use wrap instead - Inherited from:
- ClassManifestDeprecatedApis
Attributes
- Deprecated
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[Since version 2.10.0]use runtimeClass instead - Inherited from:
- ClassManifestDeprecatedApis
Attributes
- Deprecated
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[Since version 2.10.0]use wrap.newArray instead - Inherited from:
- ClassManifestDeprecatedApis
Attributes
- Deprecated
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[Since version 2.10.0]use wrap.wrap.newArray instead - Inherited from:
- ClassManifestDeprecatedApis
Attributes
- Deprecated
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[Since version 2.10.0]use wrap.wrap.wrap.newArray instead - Inherited from:
- ClassManifestDeprecatedApis
Attributes
- Deprecated
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[Since version 2.10.0]use wrap.wrap.wrap.wrap.newArray instead - Inherited from:
- ClassManifestDeprecatedApis
Attributes
- Deprecated
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[Since version 2.10.0]use ArrayBuilder.make(this) instead - Inherited from:
- ClassManifestDeprecatedApis
Attributes
- Deprecated
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[Since version 2.10.0]create WrappedArray directly instead - Inherited from:
- ClassManifestDeprecatedApis
Attributes
- Deprecated
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[Since version 2.10.0]use scala.reflect.runtime.universe.TypeTag to capture type structure instead - Inherited from:
- ClassManifestDeprecatedApis