scala.reflect.api

# Mirrors

###
Related Doc: package api

#### trait Mirrors extends AnyRef

EXPERIMENTAL

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

`Mirror`s are a central part of Scala Reflection. All information provided by reflection is made accessible through `Mirror`s. 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" `Mirror`s (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 `Mirror`s make use of only classloader `Mirror`s to load `Symbol`s by name.

The entry point to classloader `Mirror`s is via scala.reflect.macros.blackbox.Context#mirror or scala.reflect.macros.whitebox.Context#mirror. Typical methods which use classloader `Mirror`s 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 `String`s to lookup the `Symbol`.

##### Runtime Mirrors

Runtime `Mirror`s make use of both classloader and invoker `Mirror`s.

The entry point to `Mirror`s 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 `Mirror`s interact are available below.

##### Types of Mirrors, Their Use Cases & Examples

scala.reflect.api.Mirrors#ReflectiveMirror. Used for loading `Symbol`s 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 `Mirror`s 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 `Mirrors`s, see the Reflection Guide: Mirrors

Self Type
  Universe
Source
  Mirrors.scala

Linear Supertypes
AnyRef, Any
Known Subclasses
JavaUniverse, Universe, Universe
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2. AnyRef
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2. by StringFormat
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### Type Members

1. #### trait ClassMirror extends Universe.TemplateMirror

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

   A mirror that reflects the instance parts of a runtime class. See the overview page for details on how to use runtime reflection.

2. #### trait FieldMirror extends AnyRef

   A mirror that reflects a field.

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

3. #### trait InstanceMirror extends AnyRef

   A mirror that reflects a runtime value.

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

4. #### trait MethodMirror extends AnyRef

   A mirror that reflects a method.

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

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.

   A mirror that reflects a Scala object definition or the static parts of a runtime class. See the overview page for details on how to use runtime reflection.

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

   A mirror that reflects instances and static classes.

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

8. #### abstract type RuntimeClass >: Null <: AnyRef

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

9. #### trait RuntimeClassApi extends AnyRef

   Has no special methods.

   Has no special methods. Is here to provides erased identity for `RuntimeClass`.

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

    The API of a mirror for a reflective universe.

    The API of a mirror for a reflective universe. See the overview page for details on how to use runtime reflection.

11. #### trait TemplateMirror extends AnyRef

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

    A mirror that reflects the instance or static parts of a runtime class. See the overview page for details on how to use runtime reflection.

### 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: Any): Boolean

   Test two objects for inequality.

   Test two objects for inequality.

   returns

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

   Definition Classes
     AnyRef → Any

2. #### 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

3. #### def +(other: String): String

   Implicit information
     This member is added by an implicit conversion from Mirrors to any2stringadd[Mirrors] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd

4. #### def ->[B](y: B): (Mirrors, B)

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

5. #### final def ==(arg0: Any): Boolean

   The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

   The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

   arg0

     the object to compare against this object for equality.

   returns

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

   Definition Classes
     AnyRef → Any

6. #### 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`.

7. #### 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

8. #### 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 Ensuring in scala.Predef.
   Definition Classes
     Ensuring

9. #### def ensuring(cond: (Mirrors) ⇒ Boolean): Mirrors

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

10. #### 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 Ensuring in scala.Predef.
    Definition Classes
      Ensuring

11. #### def ensuring(cond: Boolean): Mirrors

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

12. #### 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

13. #### 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

14. #### 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( classOf[java.lang.Throwable] )
    Note

      not specified by SLS as a member of AnyRef

15. #### def formatted(fmtstr: String): String

    Implicit information
      This member is added by an implicit conversion from Mirrors to StringFormat[Mirrors] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()

16. #### 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

17. #### 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

18. #### 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

19. #### 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

20. #### 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

21. #### 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

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

    Definition Classes
      AnyRef

23. #### 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

24. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

25. #### final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

26. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

27. #### def →[B](y: B): (Mirrors, B)

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

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from Mirrors to any2stringadd[Mirrors]

### Inherited by implicit conversion StringFormat from Mirrors to StringFormat[Mirrors]

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

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

### Mirrors

### API

The methods available for each reflection entity, without the implementation. Since the reflection entities are later overridden by runtime reflection and macros, their API counterparts guarantee a minimum set of methods that are implemented.

### Ungrouped