Packages

  • package root
    Definition Classes
    root
  • package scala
    Definition Classes
    root
  • package reflect
    Definition Classes
    scala
  • package api

    EXPERIMENTAL

    EXPERIMENTAL

    The Scala Reflection API (located in scala-reflect.jar).

    In Scala 2.10.0, the Scala Reflection API and its implementation have an "experimental" status. This means that the API and the docs are not complete and can be changed in binary- and source-incompatible manner in 2.10.1. This also means that the implementation has some known issues.

    The following types are the backbone of the Scala Reflection API, and serve as a good starting point for information about Scala Reflection:

    For more information about Scala Reflection, see the Reflection Guide

    Definition Classes
    reflect
  • trait Mirrors extends AnyRef

    EXPERIMENTAL

    EXPERIMENTAL

    This trait provides support for Mirrors in the Scala Reflection API.

    Mirrors are a central part of Scala Reflection. All information provided by reflection is made accessible through Mirrors. Depending on the type of information to be obtained, or the reflective action to be taken, different flavors of mirrors must be used. "Classloader" mirrors can be used to obtain representations of types and members. From a classloader Mirror, it's possible to obtain more specialized "invoker" Mirrors (the most commonly-used mirrors), which implement reflective invocations, such as method/constructor calls and field accesses.

    The two flavors of mirrors:

    • “Classloader” mirrors. These mirrors translate names to symbols (via methods staticClass/staticModule/staticPackage).
    • "Invoker” mirrors. These mirrors implement reflective invocations (via methods MethodMirror.apply, FieldMirror.get, etc). These "invoker" mirrors are the types of mirrors that are most commonly used.
    Compile-time Mirrors

    Compile-time Mirrors make use of only classloader Mirrors to load Symbols by name.

    The entry point to classloader Mirrors is via scala.reflect.macros.blackbox.Context#mirror or scala.reflect.macros.whitebox.Context#mirror. Typical methods which use classloader Mirrors include scala.reflect.api.Mirror#staticClass, scala.reflect.api.Mirror#staticModule, and scala.reflect.api.Mirror#staticPackage. For example:

    import scala.reflect.macros.blackbox.Context

case class Location(filename: String, line: Int, column: Int)

object Macros {
  def currentLocation: Location = macro impl

  def impl(c: Context): c.Expr[Location] = {
    import c.universe._
    val pos = c.macroApplication.pos
    val clsLocation = c.mirror.staticModule("Location") // get symbol of "Location" object
    c.Expr(Apply(Ident(clsLocation), List(Literal(Constant(pos.source.path)), Literal(Constant(pos.line)), Literal(Constant(pos.column)))))
  }
}

    Of Note: There are several high-level alternatives that one can use to avoid having to manually lookup symbols. For example, typeOf[Location.type].termSymbol (or typeOf[Location].typeSymbol if we needed a ClassSymbol), which are type safe since we don’t have to use Strings to lookup the Symbol.

    Runtime Mirrors

    Runtime Mirrors make use of both classloader and invoker Mirrors.

    The entry point to Mirrors for use at runtime is via ru.runtimeMirror(<classloader>), where ru is scala.reflect.runtime.universe.

    The result of a scala.reflect.api.JavaUniverse#runtimeMirror call is a classloader mirror, of type scala.reflect.api.Mirrors#ReflectiveMirror, which can load symbols by names as discussed above (in the “Compile-time” section).

    A classloader mirror can create invoker mirrors, which include: scala.reflect.api.Mirrors#InstanceMirror, scala.reflect.api.Mirrors#MethodMirror, scala.reflect.api.Mirrors#FieldMirror, scala.reflect.api.Mirrors#ClassMirror and scala.reflect.api.Mirrors#ModuleMirror.

    Examples of how these two types of Mirrors interact are available below.

    Types of Mirrors, Their Use Cases & Examples

    scala.reflect.api.Mirrors#ReflectiveMirror. Used for loading Symbols by name, and as an entry point into invoker mirrors. Entry point: val m = ru.runtimeMirror(<classloader>). Example:

    scala> val ru = scala.reflect.runtime.universe
ru: scala.reflect.api.JavaUniverse = ...

scala> val m = ru.runtimeMirror(getClass.getClassLoader)
m: reflect.runtime.universe.Mirror = JavaMirror ...

    scala.reflect.api.Mirrors#InstanceMirror. Used for creating invoker Mirrors for methods and fields and for inner classes and inner objects (modules). Entry point: val im = m.reflect(<value>). Example:

    scala> class C { def x = 2 }
defined class C

scala> val im = m.reflect(new C)
im: reflect.runtime.universe.InstanceMirror = instance mirror for C@3442299e

    scala.reflect.api.Mirrors#MethodMirror. Used for invoking instance methods (Scala only has instance methods-- methods of objects are instance methods of object instances, obtainable via ModuleMirror.instance). Entry point: val mm = im.reflectMethod(<method symbol>). Example:

    scala> val methodX = typeOf[C].declaration(TermName("x")).asMethod
methodX: reflect.runtime.universe.MethodSymbol = method x

scala> val mm = im.reflectMethod(methodX)
mm: reflect.runtime.universe.MethodMirror = method mirror for C.x: scala.Int (bound to C@3442299e)

scala> mm()
res0: Any = 2

    scala.reflect.api.Mirrors#FieldMirror. Used for getting/setting instance fields (Scala only has instance fields-- fields of objects are instance methods of object instances obtainable via ModuleMirror.instance). Entry point: val fm = im.reflectMethod(<field or accessor symbol>). Example:

    scala> class C { val x = 2; val y = 3 }
defined class C

scala> val m = ru.runtimeMirror(getClass.getClassLoader)
m: reflect.runtime.universe.Mirror = JavaMirror ...

scala> val im = m.reflect(new C)
im: reflect.runtime.universe.InstanceMirror = instance mirror for C@5f0c8ac1

scala> val fieldX = typeOf[C].declaration(TermName("x")).asTerm.accessed.asTerm
fieldX: reflect.runtime.universe.TermSymbol = value x
scala> val fmX = im.reflectField(fieldX)
fmX: reflect.runtime.universe.FieldMirror = field mirror for C.x (bound to C@5f0c8ac1)

scala> fmX.get
res0: Any = 2

scala> fmX.set(3) // NOTE: can set an underlying value of an immutable field!

scala> val fieldY = typeOf[C].declaration(TermName("y")).asTerm.accessed.asTerm
fieldY: reflect.runtime.universe.TermSymbol = variable y

scala> val fmY = im.reflectField(fieldY)
fmY: reflect.runtime.universe.FieldMirror = field mirror for C.y (bound to C@5f0c8ac1)

scala> fmY.get
res1: Any = 3

scala> fmY.set(4)

scala> fmY.get
res2: Any = 4

    scala.reflect.api.Mirrors#ClassMirror. Used for creating invoker mirrors for constructors. Entry points: for static classes val cm1 = m.reflectClass(<class symbol>), for inner classes val mm2 = im.reflectClass(<class symbol>). Example:

    scala> case class C(x: Int)
defined class C

scala> val m = ru.runtimeMirror(getClass.getClassLoader)
m: reflect.runtime.universe.Mirror = JavaMirror ...

scala> val classC = typeOf[C].typeSymbol.asClass

classC: reflect.runtime.universe.Symbol = class C

scala> val cm = m.reflectClass(classC)
cm: reflect.runtime.universe.ClassMirror = class mirror for C (bound to null)

scala> val ctorC = typeOf[C].declaration(ru.nme.CONSTRUCTOR).asMethod
ctorC: reflect.runtime.universe.MethodSymbol = constructor C

scala> val ctorm = cm.reflectConstructor(ctorC)
ctorm: reflect.runtime.universe.MethodMirror = constructor mirror for C.<init>(x: scala.Int): C (bound to null)

scala> ctorm(2)
res0: Any = C(2)

    scala.reflect.api.Mirrors#ModuleMirror. Used for getting singleton instances of objects. Entry points: for static objects (modules) val mm1 = m.reflectModule(<module symbol>), for inner objects (modules) val mm2 = im.reflectModule(<module symbol>). Example:

    scala> object C { def x = 2 }
defined module C

scala> val m = ru.runtimeMirror(getClass.getClassLoader)
m: reflect.runtime.universe.Mirror = JavaMirror ...

scala> val objectC = typeOf[C.type].termSymbol.asModule
objectC: reflect.runtime.universe.ModuleSymbol = object C

scala> val mm = m.reflectModule(objectC)
mm: reflect.runtime.universe.ModuleMirror = module mirror for C (bound to null)

scala> val obj = mm.instance
obj: Any = C$@1005ec04

    For more information about Mirrorss, see the Reflection Guide: Mirrors

    Definition Classes
    api
  • ClassMirror
  • FieldMirror
  • InstanceMirror
  • MethodMirror
  • Mirror
  • ModuleMirror
  • ReflectiveMirror
  • RuntimeClass
  • RuntimeClassApi
  • RuntimeMirror
  • TemplateMirror
t

scala.reflect.api.Mirrors

ReflectiveMirror

trait ReflectiveMirror extends api.Mirror[Mirrors.this.type]

A mirror that reflects instances and static classes. See the overview page for details on how to use runtime reflection.

Source
Mirrors.scala
Linear Supertypes
api.Mirror[Mirrors.this.type], AnyRef, Any
Known Subclasses
JavaMirror, RuntimeMirror
Ordering
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  2. Alphabetic
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Inherited
  1. ReflectiveMirror
  2. Mirror
  3. AnyRef
  4. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Visibility
  1. Public
  2. All

Mirror

  1. abstract def EmptyPackage: Universe.ModuleSymbol

    The module symbol of the default (unnamed) package

    The module symbol of the default (unnamed) package

    Definition Classes
    Mirror
  2. abstract def EmptyPackageClass: Universe.ClassSymbol

    The module class symbol of the default (unnamed) package

    The module class symbol of the default (unnamed) package

    Definition Classes
    Mirror
  3. abstract def RootClass: Universe.ClassSymbol

    The class symbol of the _root_ package

    The class symbol of the _root_ package

    Definition Classes
    Mirror
  4. abstract def RootPackage: Universe.ModuleSymbol

    The module symbol of the _root_ package

    The module symbol of the _root_ package

    Definition Classes
    Mirror
  5. abstract def staticClass(fullName: String): Universe.ClassSymbol

    The symbol corresponding to the globally accessible class with the given fully qualified name fullName.

    The symbol corresponding to the globally accessible class with the given fully qualified name fullName.

    If the name points to a type alias, it's recursively dealiased and its target is returned. If you need a symbol that corresponds to the type alias itself, load it directly from the package class:

    scala> cm.staticClass("scala.List") res0: scala.reflect.runtime.universe.ClassSymbol = class List

    scala> res0.fullName res1: String = scala.collection.immutable.List

    scala> cm.staticPackage("scala") res2: scala.reflect.runtime.universe.ModuleSymbol = package scala

    scala> res2.moduleClass.info member TypeName("List") res3: scala.reflect.runtime.universe.Symbol = type List

    scala> res3.fullName res4: String = scala.List

    To be consistent with Scala name resolution rules, in case of ambiguity between a package and an object, the object is never been considered.

    For example for the following code:

    package foo { class B }

    object foo { class A class B }

    staticClass("foo.B") will resolve to the symbol corresponding to the class B declared in the package foo, and staticClass("foo.A") will throw a ScalaReflectionException.

    In the example above, to load a symbol that corresponds to the class B declared in the object foo, use staticModule("foo") to load the module symbol and then navigate info.members of its moduleClass.

    Definition Classes
    Mirror
  6. abstract def staticModule(fullName: String): Universe.ModuleSymbol

    The symbol corresponding to the globally accessible object with the given fully qualified name fullName.

    The symbol corresponding to the globally accessible object with the given fully qualified name fullName.

    To be consistent with Scala name resolution rules, in case of ambiguity between a package and an object, the object is never been considered.

    For example for the following code:

    package foo { object B }

    object foo { object A object B }

    staticModule("foo.B") will resolve to the symbol corresponding to the object B declared in the package foo, and staticModule("foo.A") will throw a ScalaReflectionException

    In the example above, to load a symbol that corresponds to the object B declared in the object foo, use staticModule("foo") to load the module symbol and then navigate info.members of its moduleClass.

    Definition Classes
    Mirror
  7. abstract def staticPackage(fullName: String): Universe.ModuleSymbol

    The symbol corresponding to a package with the given fully qualified name fullName.

    The symbol corresponding to a package with the given fully qualified name fullName.

    Definition Classes
    Mirror
  8. abstract val universe: Mirrors.this.type

    The universe this mirror belongs to.

    The universe this mirror belongs to.

    Definition Classes
    Mirror

TypeTags

  1. abstract def symbolOf[T](implicit arg0: Universe.WeakTypeTag[T]): Universe.TypeSymbol

    Type symbol of x as derived from a type tag.

    Type symbol of x as derived from a type tag.

    Definition Classes
    Mirror
  2. def typeOf[T](implicit arg0: Universe.TypeTag[T]): Universe.Type

    Shortcut for implicitly[TypeTag[T]].tpe

    Shortcut for implicitly[TypeTag[T]].tpe

    Definition Classes
    Mirror
  3. def weakTypeOf[T](implicit arg0: Universe.WeakTypeTag[T]): Universe.Type

    Shortcut for implicitly[WeakTypeTag[T]].tpe

    Shortcut for implicitly[WeakTypeTag[T]].tpe

    Definition Classes
    Mirror

Ungrouped

  1. abstract def reflect[T](obj: T)(implicit arg0: ClassTag[T]): Universe.InstanceMirror

    A reflective mirror for the given object.

    A reflective mirror for the given object.

    Such a mirror can be used to further reflect against the members of the object to get/set fields, invoke methods and inspect inner classes and objects.

  2. abstract def reflectClass(cls: Universe.ClassSymbol): Universe.ClassMirror

    Reflects against a static class symbol and returns a mirror that can be used to create instances of the class, inspect its companion object or perform further reflections.

    Reflects against a static class symbol and returns a mirror that can be used to create instances of the class, inspect its companion object or perform further reflections.

    To get a class symbol by the name of the class you would like to reflect, use <this mirror>.classSymbol(<runtime class loaded by its name>).

    The input symbol can be either private or non-private (Scala reflection transparently deals with visibility). It must be static, i.e. either top-level or nested within one or several static objects.

  3. abstract def reflectModule(mod: Universe.ModuleSymbol): Universe.ModuleMirror

    Reflects against a static module symbol and returns a mirror that can be used to get the instance of the object or inspect its companion class.

    Reflects against a static module symbol and returns a mirror that can be used to get the instance of the object or inspect its companion class.

    To get a module symbol by the name of its companion class you would like to reflect, use <this mirror>.classSymbol(<runtime class loaded by its name>).companion.get.

    The input symbol can be either private or non-private (Scala reflection transparently deals with visibility). It must be static, i.e. either top-level or nested within one or several static objects.