Mixing
Calling method via reflection in Scala
I want to call an arbitrary public method of an arbitrary stuff via reflection. I.e. let's say, I want to write method extractMethod to be used like:
class User { def setAvatar(avatar: Avatar): Unit = …; … }
val m = extractMethod(someUser, "setAvatar")
m(someAvatar)
From the Reflection. Overview document from Scala docs, I see the following direct way to do that:
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod[Stuff: ClassTag: TypeTag](
stuff: Stuff,
methodName: String): MethodMirror =
{
val stuffTypeTag = typeTag[Stuff]
val mirror = stuffTypeTag.mirror
val stuffType = stuffTypeTag.tpe
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)
.reflectMethod(methodSymbol)
}
However what I'm bothered with this solution is that I need to pass implicit ClassTag[Stuff] and TypeTag[Stuff] parameters (first one is needed for calling reflect, second one — for getting stuffType). Which may be quite cumbersome, especially if extractMethod is called from generics that are called from generics and so on. I'd accept this as necessity for some languages that strongly lack runtime type information, but Scala is based on JRE, which allows to do the following:
def extractMethod[Stuff](
stuff: Stuff,
methodName: String,
parameterTypes: Array[Class[_]]): (Object*) => Object =
{
val unboundMethod = stuff.getClass()
.getMethod(methodName, parameterTypes: _*)
arguments => unboundMethod(stuff, arguments: _*)
}
I understand that Scala reflection allows to get more information that basic Java reflection. Still, here I just need to call a method. Is there a way to somehow reduce requirements (e.g. these ClassTag, TypeTag) of the Scala-reflection-based extractMethod version (without falling back to pure-Java reflection), assuming that performance doesn't matter for me?
scala reflection scala-reflect
asked Nov 22 '18 at 12:29
SashaSasha
1,6431529
add a comment |
I want to call an arbitrary public method of an arbitrary stuff via reflection. I.e. let's say, I want to write method extractMethod to be used like:
class User { def setAvatar(avatar: Avatar): Unit = …; … }
val m = extractMethod(someUser, "setAvatar")
m(someAvatar)
From the Reflection. Overview document from Scala docs, I see the following direct way to do that:
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod[Stuff: ClassTag: TypeTag](
stuff: Stuff,
methodName: String): MethodMirror =
{
val stuffTypeTag = typeTag[Stuff]
val mirror = stuffTypeTag.mirror
val stuffType = stuffTypeTag.tpe
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)
.reflectMethod(methodSymbol)
}
However what I'm bothered with this solution is that I need to pass implicit ClassTag[Stuff] and TypeTag[Stuff] parameters (first one is needed for calling reflect, second one — for getting stuffType). Which may be quite cumbersome, especially if extractMethod is called from generics that are called from generics and so on. I'd accept this as necessity for some languages that strongly lack runtime type information, but Scala is based on JRE, which allows to do the following:
def extractMethod[Stuff](
stuff: Stuff,
methodName: String,
parameterTypes: Array[Class[_]]): (Object*) => Object =
{
val unboundMethod = stuff.getClass()
.getMethod(methodName, parameterTypes: _*)
arguments => unboundMethod(stuff, arguments: _*)
}
I understand that Scala reflection allows to get more information that basic Java reflection. Still, here I just need to call a method. Is there a way to somehow reduce requirements (e.g. these ClassTag, TypeTag) of the Scala-reflection-based extractMethod version (without falling back to pure-Java reflection), assuming that performance doesn't matter for me?
scala reflection scala-reflect
asked Nov 22 '18 at 12:29
SashaSasha
1,6431529
add a comment |
I want to call an arbitrary public method of an arbitrary stuff via reflection. I.e. let's say, I want to write method extractMethod to be used like:
class User { def setAvatar(avatar: Avatar): Unit = …; … }
val m = extractMethod(someUser, "setAvatar")
m(someAvatar)
From the Reflection. Overview document from Scala docs, I see the following direct way to do that:
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod[Stuff: ClassTag: TypeTag](
stuff: Stuff,
methodName: String): MethodMirror =
{
val stuffTypeTag = typeTag[Stuff]
val mirror = stuffTypeTag.mirror
val stuffType = stuffTypeTag.tpe
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)
.reflectMethod(methodSymbol)
}
However what I'm bothered with this solution is that I need to pass implicit ClassTag[Stuff] and TypeTag[Stuff] parameters (first one is needed for calling reflect, second one — for getting stuffType). Which may be quite cumbersome, especially if extractMethod is called from generics that are called from generics and so on. I'd accept this as necessity for some languages that strongly lack runtime type information, but Scala is based on JRE, which allows to do the following:
def extractMethod[Stuff](
stuff: Stuff,
methodName: String,
parameterTypes: Array[Class[_]]): (Object*) => Object =
{
val unboundMethod = stuff.getClass()
.getMethod(methodName, parameterTypes: _*)
arguments => unboundMethod(stuff, arguments: _*)
}
I understand that Scala reflection allows to get more information that basic Java reflection. Still, here I just need to call a method. Is there a way to somehow reduce requirements (e.g. these ClassTag, TypeTag) of the Scala-reflection-based extractMethod version (without falling back to pure-Java reflection), assuming that performance doesn't matter for me?
scala reflection scala-reflect
asked Nov 22 '18 at 12:29
SashaSasha
1,6431529
I want to call an arbitrary public method of an arbitrary stuff via reflection. I.e. let's say, I want to write method extractMethod to be used like:
class User { def setAvatar(avatar: Avatar): Unit = …; … }
val m = extractMethod(someUser, "setAvatar")
m(someAvatar)
From the Reflection. Overview document from Scala docs, I see the following direct way to do that:
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod[Stuff: ClassTag: TypeTag](
stuff: Stuff,
methodName: String): MethodMirror =
{
val stuffTypeTag = typeTag[Stuff]
val mirror = stuffTypeTag.mirror
val stuffType = stuffTypeTag.tpe
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)
.reflectMethod(methodSymbol)
}
However what I'm bothered with this solution is that I need to pass implicit ClassTag[Stuff] and TypeTag[Stuff] parameters (first one is needed for calling reflect, second one — for getting stuffType). Which may be quite cumbersome, especially if extractMethod is called from generics that are called from generics and so on. I'd accept this as necessity for some languages that strongly lack runtime type information, but Scala is based on JRE, which allows to do the following:
def extractMethod[Stuff](
stuff: Stuff,
methodName: String,
parameterTypes: Array[Class[_]]): (Object*) => Object =
{
val unboundMethod = stuff.getClass()
.getMethod(methodName, parameterTypes: _*)
arguments => unboundMethod(stuff, arguments: _*)
}
I understand that Scala reflection allows to get more information that basic Java reflection. Still, here I just need to call a method. Is there a way to somehow reduce requirements (e.g. these ClassTag, TypeTag) of the Scala-reflection-based extractMethod version (without falling back to pure-Java reflection), assuming that performance doesn't matter for me?
scala reflection scala-reflect
scala reflection scala-reflect
asked Nov 22 '18 at 12:29
SashaSasha
1,6431529
asked Nov 22 '18 at 12:29
SashaSasha
1,6431529
asked Nov 22 '18 at 12:29
SashaSasha
1,6431529
asked Nov 22 '18 at 12:29
SashaSasha
1,6431529
asked Nov 22 '18 at 12:29
SashaSasha
1,6431529
1,6431529
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
Yes, there is.
First, according to this answer,
TypeTag[Stuff]is a strictly stronger requirement thanClassTag[Stuff]. Although we don't automatically get implicitClassTag[Stuff]from implicitTypeTag[Stuff], we can evaluate it manually asClassTag[Stuff](stuffTypeTag.mirror.runtimeClass(stuffTypeTag.tpe))and then implicitly or explicitly pass it toreflectthat needs it:
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod[Stuff: TypeTag](
stuff: Stuff,
methodName: String): MethodMirror =
{
val stuffTypeTag = typeTag[Stuff]
val mirror = stuffTypeTag.mirror
val stuffType = stuffTypeTag.tpe
val stuffClassTag = ClassTag[Stuff](mirror.runtimeClass(stuffType))
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)(stuffClassTag)
.reflectMethod(methodSymbol)
}
Second,
mirrorandstuffTypecan be obtained fromstuff.getClass():
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod(stuff: Stuff, methodName: String): MethodMirror = {
val stuffClass = stuff.getClass()
val mirror = runtimeMirror(stuffClass.getClassLoader)
val stuffType = mirror.classSymbol(stuffClass).toType
val stuffClassTag = ClassTag[Stuff](mirror.runtimeClass(stuffType))
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)(stuffClassTag)
.reflectMethod(methodSymbol)
}
Therefore we obtained Scala-style reflection entities (i.e. finally MethodMirror) without requiring ClassTag and/or TypeTag to be passed explicitly or implicitly from the caller. Not sure, however, how it compares with the ways described in the question (i.e. passing tags from outside and pure Java) in the terms of performance.
answered Nov 22 '18 at 12:29
SashaSasha
1,6431529
add a comment |
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1 Answer
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1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Yes, there is.
First, according to this answer,
TypeTag[Stuff]is a strictly stronger requirement thanClassTag[Stuff]. Although we don't automatically get implicitClassTag[Stuff]from implicitTypeTag[Stuff], we can evaluate it manually asClassTag[Stuff](stuffTypeTag.mirror.runtimeClass(stuffTypeTag.tpe))and then implicitly or explicitly pass it toreflectthat needs it:
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod[Stuff: TypeTag](
stuff: Stuff,
methodName: String): MethodMirror =
{
val stuffTypeTag = typeTag[Stuff]
val mirror = stuffTypeTag.mirror
val stuffType = stuffTypeTag.tpe
val stuffClassTag = ClassTag[Stuff](mirror.runtimeClass(stuffType))
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)(stuffClassTag)
.reflectMethod(methodSymbol)
}
Second,
mirrorandstuffTypecan be obtained fromstuff.getClass():
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod(stuff: Stuff, methodName: String): MethodMirror = {
val stuffClass = stuff.getClass()
val mirror = runtimeMirror(stuffClass.getClassLoader)
val stuffType = mirror.classSymbol(stuffClass).toType
val stuffClassTag = ClassTag[Stuff](mirror.runtimeClass(stuffType))
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)(stuffClassTag)
.reflectMethod(methodSymbol)
}
Therefore we obtained Scala-style reflection entities (i.e. finally MethodMirror) without requiring ClassTag and/or TypeTag to be passed explicitly or implicitly from the caller. Not sure, however, how it compares with the ways described in the question (i.e. passing tags from outside and pure Java) in the terms of performance.
answered Nov 22 '18 at 12:29
SashaSasha
1,6431529
add a comment |
Yes, there is.
First, according to this answer,
TypeTag[Stuff]is a strictly stronger requirement thanClassTag[Stuff]. Although we don't automatically get implicitClassTag[Stuff]from implicitTypeTag[Stuff], we can evaluate it manually asClassTag[Stuff](stuffTypeTag.mirror.runtimeClass(stuffTypeTag.tpe))and then implicitly or explicitly pass it toreflectthat needs it:
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod[Stuff: TypeTag](
stuff: Stuff,
methodName: String): MethodMirror =
{
val stuffTypeTag = typeTag[Stuff]
val mirror = stuffTypeTag.mirror
val stuffType = stuffTypeTag.tpe
val stuffClassTag = ClassTag[Stuff](mirror.runtimeClass(stuffType))
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)(stuffClassTag)
.reflectMethod(methodSymbol)
}
Second,
mirrorandstuffTypecan be obtained fromstuff.getClass():
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod(stuff: Stuff, methodName: String): MethodMirror = {
val stuffClass = stuff.getClass()
val mirror = runtimeMirror(stuffClass.getClassLoader)
val stuffType = mirror.classSymbol(stuffClass).toType
val stuffClassTag = ClassTag[Stuff](mirror.runtimeClass(stuffType))
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)(stuffClassTag)
.reflectMethod(methodSymbol)
}
Therefore we obtained Scala-style reflection entities (i.e. finally MethodMirror) without requiring ClassTag and/or TypeTag to be passed explicitly or implicitly from the caller. Not sure, however, how it compares with the ways described in the question (i.e. passing tags from outside and pure Java) in the terms of performance.
answered Nov 22 '18 at 12:29
SashaSasha
1,6431529
add a comment |
Yes, there is.
First, according to this answer,
TypeTag[Stuff]is a strictly stronger requirement thanClassTag[Stuff]. Although we don't automatically get implicitClassTag[Stuff]from implicitTypeTag[Stuff], we can evaluate it manually asClassTag[Stuff](stuffTypeTag.mirror.runtimeClass(stuffTypeTag.tpe))and then implicitly or explicitly pass it toreflectthat needs it:
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod[Stuff: TypeTag](
stuff: Stuff,
methodName: String): MethodMirror =
{
val stuffTypeTag = typeTag[Stuff]
val mirror = stuffTypeTag.mirror
val stuffType = stuffTypeTag.tpe
val stuffClassTag = ClassTag[Stuff](mirror.runtimeClass(stuffType))
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)(stuffClassTag)
.reflectMethod(methodSymbol)
}
Second,
mirrorandstuffTypecan be obtained fromstuff.getClass():
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod(stuff: Stuff, methodName: String): MethodMirror = {
val stuffClass = stuff.getClass()
val mirror = runtimeMirror(stuffClass.getClassLoader)
val stuffType = mirror.classSymbol(stuffClass).toType
val stuffClassTag = ClassTag[Stuff](mirror.runtimeClass(stuffType))
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)(stuffClassTag)
.reflectMethod(methodSymbol)
}
Therefore we obtained Scala-style reflection entities (i.e. finally MethodMirror) without requiring ClassTag and/or TypeTag to be passed explicitly or implicitly from the caller. Not sure, however, how it compares with the ways described in the question (i.e. passing tags from outside and pure Java) in the terms of performance.
answered Nov 22 '18 at 12:29
SashaSasha
1,6431529
Yes, there is.
First, according to this answer,
TypeTag[Stuff]is a strictly stronger requirement thanClassTag[Stuff]. Although we don't automatically get implicitClassTag[Stuff]from implicitTypeTag[Stuff], we can evaluate it manually asClassTag[Stuff](stuffTypeTag.mirror.runtimeClass(stuffTypeTag.tpe))and then implicitly or explicitly pass it toreflectthat needs it:
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod[Stuff: TypeTag](
stuff: Stuff,
methodName: String): MethodMirror =
{
val stuffTypeTag = typeTag[Stuff]
val mirror = stuffTypeTag.mirror
val stuffType = stuffTypeTag.tpe
val stuffClassTag = ClassTag[Stuff](mirror.runtimeClass(stuffType))
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)(stuffClassTag)
.reflectMethod(methodSymbol)
}
Second,
mirrorandstuffTypecan be obtained fromstuff.getClass():
import scala.reflect.ClassTag
import scala.reflect.runtime.universe._
def extractMethod(stuff: Stuff, methodName: String): MethodMirror = {
val stuffClass = stuff.getClass()
val mirror = runtimeMirror(stuffClass.getClassLoader)
val stuffType = mirror.classSymbol(stuffClass).toType
val stuffClassTag = ClassTag[Stuff](mirror.runtimeClass(stuffType))
val methodSymbol = stuffType
.member(TermName(methodName)).asMethod
mirror.reflect(stuff)(stuffClassTag)
.reflectMethod(methodSymbol)
}
Therefore we obtained Scala-style reflection entities (i.e. finally MethodMirror) without requiring ClassTag and/or TypeTag to be passed explicitly or implicitly from the caller. Not sure, however, how it compares with the ways described in the question (i.e. passing tags from outside and pure Java) in the terms of performance.
answered Nov 22 '18 at 12:29
SashaSasha
1,6431529
answered Nov 22 '18 at 12:29
SashaSasha
1,6431529
answered Nov 22 '18 at 12:29
SashaSasha
1,6431529
answered Nov 22 '18 at 12:29
SashaSasha
1,6431529
1,6431529
add a comment |
add a comment |
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