scala.reflect.api

Mirrors

trait Mirrors extends AnyRef

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:

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.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.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.JavaMirrors#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 [email protected]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(newTermName("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 [email protected]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 [email protected]5f0c8ac1

scala> val fieldX = typeOf[C].declaration(newTermName("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 [email protected]5f0c8ac1)

scala> fmX.get
res0: Any = 2

scala> fmX.set(3)
scala.ScalaReflectionException: cannot set an immutable field x
...

scala> val fieldY = typeOf[C].declaration(newTermName("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 [email protected]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(<module 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 = [email protected]1005ec04

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

Self Type
Universe
Source
Mirrors.scala
Linear Supertypes
Known Subclasses
Type Hierarchy Learn more about scaladoc diagrams
Content Hierarchy Learn more about scaladoc diagrams
Ordering
  1. Grouped
  2. Alphabetic
  3. By inheritance
Inherited
  1. Mirrors
  2. AnyRef
  3. Any
Implicitly
  1. by any2stringadd
  2. by any2stringfmt
  3. by any2ArrowAssoc
  4. by any2Ensuring
  1. Hide All
  2. Show all
Learn more about member selection
Visibility
  1. Public
  2. All

Type Members

  1. trait ClassMirror extends Universe.TemplateMirror

    A mirror that reflects the instance parts of a runtime class.

  2. trait FieldMirror extends AnyRef

    A mirror that reflects a field.

  3. trait InstanceMirror extends AnyRef

    A mirror that reflects a runtime value.

  4. trait MethodMirror extends AnyRef

    A mirror that reflects a method.

  5. abstract type Mirror >: Null <: api.Mirror[Mirrors.this.type]

    The base type of all mirrors of this universe.

    The base type of all mirrors of this universe.

    This abstract type conforms the base interface for all mirrors defined in scala.reflect.api.Mirror and is gradually refined in specific universes (e.g. Mirror of a scala.reflect.api.JavaUniverse is capable of reflection).

  6. trait ModuleMirror extends Universe.TemplateMirror

    A mirror that reflects a Scala object definition or the static parts of a runtime class.

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

    A mirror that reflects instances and static classes.

  8. abstract type RuntimeClass >: Null

    Abstracts the runtime representation of a class on the underlying platform.

  9. trait RuntimeMirror extends api.Mirror[Mirrors.this.type] with Universe.ReflectiveMirror

    The API of a mirror for a reflective universe.

  10. trait TemplateMirror extends AnyRef

    A mirror that reflects the instance or static parts of a runtime class.

Abstract Value Members

  1. abstract val rootMirror: Universe.Mirror

    The root mirror of this universe.

    The root mirror of this universe. This mirror contains standard Scala classes and types such as Any, AnyRef, AnyVal, Nothing, Null, and all classes loaded from scala-library, which are shared across all mirrors within the enclosing universe.

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 Mirrors to StringAdd performed by method any2stringadd in scala.Predef.
    Definition Classes
    StringAdd
  5. def ->[B](y: B): (Mirrors, B)

    Implicit information
    This member is added by an implicit conversion from Mirrors to ArrowAssoc[Mirrors] 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 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[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
    Note

    not specified by SLS as a member of AnyRef

  10. def ensuring(cond: (Mirrors) ⇒ Boolean, msg: ⇒ Any): Mirrors

    Implicit information
    This member is added by an implicit conversion from Mirrors to Ensuring[Mirrors] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  11. def ensuring(cond: (Mirrors) ⇒ Boolean): Mirrors

    Implicit information
    This member is added by an implicit conversion from Mirrors to Ensuring[Mirrors] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  12. def ensuring(cond: Boolean, msg: ⇒ Any): Mirrors

    Implicit information
    This member is added by an implicit conversion from Mirrors to Ensuring[Mirrors] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  13. def ensuring(cond: Boolean): Mirrors

    Implicit information
    This member is added by an implicit conversion from Mirrors to Ensuring[Mirrors] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  14. 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
  15. def equals(arg0: Any): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to eq.

    See also equals in scala.Any.

    returns

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

    Definition Classes
    AnyRef → Any
  16. 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[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
    Note

    not specified by SLS as a member of AnyRef

  17. 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 Mirrors to StringFormat performed by method any2stringfmt in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  18. 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

  19. def hashCode(): Int

    The hashCode method for reference types.

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

    returns

    the hash code value for this object.

    Definition Classes
    AnyRef → Any
  20. 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
  21. 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
  22. 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

  23. 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

  24. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef
  25. 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
    AnyRef → Any
  26. final def wait(): Unit

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

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

    Definition Classes
    AnyRef
    Annotations
    @throws()
  29. def [B](y: B): (Mirrors, B)

    Implicit information
    This member is added by an implicit conversion from Mirrors to ArrowAssoc[Mirrors] performed by method any2ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Shadowed Implict Value Members

  1. val self: Any

    Implicit information
    This member is added by an implicit conversion from Mirrors to StringAdd performed by method any2stringadd in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (mirrors: StringAdd).self
    Definition Classes
    StringAdd
  2. val self: Any

    Implicit information
    This member is added by an implicit conversion from Mirrors to StringFormat performed by method any2stringfmt in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (mirrors: StringFormat).self
    Definition Classes
    StringFormat

Deprecated Value Members

  1. def x: Mirrors

    Implicit information
    This member is added by an implicit conversion from Mirrors to ArrowAssoc[Mirrors] performed by method any2ArrowAssoc in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (mirrors: ArrowAssoc[Mirrors]).x
    Definition Classes
    ArrowAssoc
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) Use leftOfArrow instead

  2. def x: Mirrors

    Implicit information
    This member is added by an implicit conversion from Mirrors to Ensuring[Mirrors] performed by method any2Ensuring in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (mirrors: Ensuring[Mirrors]).x
    Definition Classes
    Ensuring
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) Use resultOfEnsuring instead

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from Mirrors to StringAdd

Inherited by implicit conversion any2stringfmt from Mirrors to StringFormat

Inherited by implicit conversion any2ArrowAssoc from Mirrors to ArrowAssoc[Mirrors]

Inherited by implicit conversion any2Ensuring from Mirrors to Ensuring[Mirrors]

Mirrors

Ungrouped