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].decl(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].decl(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].decl(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].decl(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

trait FieldMirror extends AnyRef

A mirror that reflects a field. See the overview page for details on how to use runtime reflection.

Source
Mirrors.scala
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Inherited
  1. FieldMirror
  2. AnyRef
  3. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Visibility
  1. Public
  2. Protected

Abstract Value Members

  1. abstract def bind(newReceiver: Any): Universe.FieldMirror

    Creates a new mirror which uses the same symbol, but is bound to a different receiver.

    Creates a new mirror which uses the same symbol, but is bound to a different receiver. This is significantly faster than recreating the mirror from scratch.

  2. abstract def get: Any

    Retrieves the value stored in the field.

    Retrieves the value stored in the field.

    Scala reflection uses reflection capabilities of the underlying platform, so FieldMirror.get might throw platform-specific exceptions associated with getting a field or invoking a getter method of the field.

    If symbol represents a field of a base class with respect to the class of the receiver, and this base field is overridden in the class of the receiver, then this method will retrieve the value of the base field. To achieve overriding behavior, use reflectMethod on an accessor.

  3. abstract def receiver: Any

    The object containing the field

  4. abstract def set(value: Any): Unit

    Updates the value stored in the field.

    Updates the value stored in the field.

    If a field is immutable, a ScalaReflectionException will be thrown.

    Scala reflection uses reflection capabilities of the underlying platform, so FieldMirror.get might throw platform-specific exceptions associated with setting a field or invoking a setter method of the field.

    If symbol represents a field of a base class with respect to the class of the receiver, and this base field is overridden in the class of the receiver, then this method will set the value of the base field. To achieve overriding behavior, use reflectMethod on an accessor.

  5. abstract def symbol: Universe.TermSymbol

    The field symbol representing the field.

    The field symbol representing the field.

    In Scala val and var declarations are usually compiled down to a pair of a backing field and corresponding accessor/accessors, which means that a single declaration might correspond to up to three different symbols. Nevertheless the FieldMirror.symbol field always points to a backing field symbol.

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
    This member is added by an implicit conversion from Universe.FieldMirror toany2stringadd[Universe.FieldMirror] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. def ->[B](y: B): (Universe.FieldMirror, B)
    Implicit
    This member is added by an implicit conversion from Universe.FieldMirror toArrowAssoc[Universe.FieldMirror] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  5. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  6. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  7. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @native()
  8. def ensuring(cond: (Universe.FieldMirror) => Boolean, msg: => Any): Universe.FieldMirror
    Implicit
    This member is added by an implicit conversion from Universe.FieldMirror toEnsuring[Universe.FieldMirror] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  9. def ensuring(cond: (Universe.FieldMirror) => Boolean): Universe.FieldMirror
    Implicit
    This member is added by an implicit conversion from Universe.FieldMirror toEnsuring[Universe.FieldMirror] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  10. def ensuring(cond: Boolean, msg: => Any): Universe.FieldMirror
    Implicit
    This member is added by an implicit conversion from Universe.FieldMirror toEnsuring[Universe.FieldMirror] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  11. def ensuring(cond: Boolean): Universe.FieldMirror
    Implicit
    This member is added by an implicit conversion from Universe.FieldMirror toEnsuring[Universe.FieldMirror] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  12. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  13. def equals(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef → Any
  14. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.Throwable])
  15. final def getClass(): Class[_ <: AnyRef]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  16. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  17. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  18. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  19. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  20. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  21. final def synchronized[T0](arg0: => T0): T0
    Definition Classes
    AnyRef
  22. def toString(): String
    Definition Classes
    AnyRef → Any
  23. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  24. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  25. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()

Deprecated Value Members

  1. def formatted(fmtstr: String): String
    Implicit
    This member is added by an implicit conversion from Universe.FieldMirror toStringFormat[Universe.FieldMirror] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @deprecated @inline()
    Deprecated

    (Since version 2.12.16) Use formatString.format(value) instead of value.formatted(formatString), or use the f"" string interpolator. In Java 15 and later, formatted resolves to the new method in String which has reversed parameters.

  2. def [B](y: B): (Universe.FieldMirror, B)
    Implicit
    This member is added by an implicit conversion from Universe.FieldMirror toArrowAssoc[Universe.FieldMirror] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Use -> instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd fromUniverse.FieldMirror to any2stringadd[Universe.FieldMirror]

Inherited by implicit conversion StringFormat fromUniverse.FieldMirror to StringFormat[Universe.FieldMirror]

Inherited by implicit conversion Ensuring fromUniverse.FieldMirror to Ensuring[Universe.FieldMirror]

Inherited by implicit conversion ArrowAssoc fromUniverse.FieldMirror to ArrowAssoc[Universe.FieldMirror]

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