Scala reflection: can I see if something is a (case) object?
1
Is there a way in Scala to see if a class was defined as an object?
def isObject(c: Class[_]): Boolean = ???
object X
class Y
val x = X
val y = new Y
isObject(x.getClass) == true
isObject(y.getClass) == false
scala reflection
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64966
add a comment |
1
Is there a way in Scala to see if a class was defined as an object?
def isObject(c: Class[_]): Boolean = ???
object X
class Y
val x = X
val y = new Y
isObject(x.getClass) == true
isObject(y.getClass) == false
scala reflection
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64966
2
Why is this important for you? What difference is for you betweenval obj = new Yorval obj = new AnyRef { }orobject obj {}?
– Suma
Nov 23 '18 at 18:52
It's not important, just curiosity.
– jqno
Nov 25 '18 at 8:14
add a comment |
1
1
1
1
Is there a way in Scala to see if a class was defined as an object?
def isObject(c: Class[_]): Boolean = ???
object X
class Y
val x = X
val y = new Y
isObject(x.getClass) == true
isObject(y.getClass) == false
scala reflection
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64966
Is there a way in Scala to see if a class was defined as an object?
def isObject(c: Class[_]): Boolean = ???
object X
class Y
val x = X
val y = new Y
isObject(x.getClass) == true
isObject(y.getClass) == false
scala reflection
scala reflection
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64966
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64966
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64966
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64966
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64966
11.1k64966
2
Why is this important for you? What difference is for you betweenval obj = new Yorval obj = new AnyRef { }orobject obj {}?
– Suma
Nov 23 '18 at 18:52
It's not important, just curiosity.
– jqno
Nov 25 '18 at 8:14
add a comment |
2
Why is this important for you? What difference is for you betweenval obj = new Yorval obj = new AnyRef { }orobject obj {}?
– Suma
Nov 23 '18 at 18:52
It's not important, just curiosity.
– jqno
Nov 25 '18 at 8:14
2
2
Why is this important for you? What difference is for you between
val obj = new Y or val obj = new AnyRef { } or object obj {}?– Suma
Nov 23 '18 at 18:52
Why is this important for you? What difference is for you between
val obj = new Y or val obj = new AnyRef { } or object obj {}?– Suma
Nov 23 '18 at 18:52
It's not important, just curiosity.
– jqno
Nov 25 '18 at 8:14
It's not important, just curiosity.
– jqno
Nov 25 '18 at 8:14
add a comment |
2 Answers
2
active
oldest
votes
4
Using scala-reflect, following seems to work:
object ObjectReflection extends App {
import scala.reflect.runtime.universe._
def isObject[T](x: T)(implicit tag: TypeTag[T]): Boolean = PartialFunction.cond(tag.tpe) {
case SingleType(_, _) => true
}
object AnObject
case object ACaseObject
class AClass
case class ACaseClass(i: Int)
trait ATrait
println("new AClass " + isObject(new AClass))
println("ACaseClass(42) " + isObject(ACaseClass(42)))
println("new ATrait {} " + isObject(new ATrait {}))
println("AnObject " + isObject(AnObject))
println("ACaseObject " + isObject(ACaseObject))
}
Prints:
new AClass false
ACaseClass(42) false
new ATrait {} false
AnObject true
ACaseObject true
Depends on:
libraryDependencies += "org.scala-lang" % "scala-reflect" % scalaVersion.value
edited Nov 25 '18 at 8:50
Suma
21.6k891155
answered Nov 24 '18 at 9:03
ygorygor
1,111615
I hardcoded scala version into the dependency, which is quite wrong. Thanks @Suma for the edit ! Also edited: stackoverflow.com/questions/53326545/… and stackoverflow.com/questions/53391593/…
– ygor
Nov 25 '18 at 11:38
add a comment |
1
As a first approximation, you can do
def isObject(c: Class[_]): Boolean = c.getName.endsWith("$")
because the anonymous class created for a singleton object y has name y$, and the usual anonymous classes (such as new AnyRef {}) end in $<number> instead.
But it's legal to create class y$ as well, which would give a false positive; such names are rare in practice, though.
Using scala-reflect should allow a more precise answer.
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
107k25212353
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
4
Using scala-reflect, following seems to work:
object ObjectReflection extends App {
import scala.reflect.runtime.universe._
def isObject[T](x: T)(implicit tag: TypeTag[T]): Boolean = PartialFunction.cond(tag.tpe) {
case SingleType(_, _) => true
}
object AnObject
case object ACaseObject
class AClass
case class ACaseClass(i: Int)
trait ATrait
println("new AClass " + isObject(new AClass))
println("ACaseClass(42) " + isObject(ACaseClass(42)))
println("new ATrait {} " + isObject(new ATrait {}))
println("AnObject " + isObject(AnObject))
println("ACaseObject " + isObject(ACaseObject))
}
Prints:
new AClass false
ACaseClass(42) false
new ATrait {} false
AnObject true
ACaseObject true
Depends on:
libraryDependencies += "org.scala-lang" % "scala-reflect" % scalaVersion.value
edited Nov 25 '18 at 8:50
Suma
21.6k891155
answered Nov 24 '18 at 9:03
ygorygor
1,111615
I hardcoded scala version into the dependency, which is quite wrong. Thanks @Suma for the edit ! Also edited: stackoverflow.com/questions/53326545/… and stackoverflow.com/questions/53391593/…
– ygor
Nov 25 '18 at 11:38
add a comment |
4
Using scala-reflect, following seems to work:
object ObjectReflection extends App {
import scala.reflect.runtime.universe._
def isObject[T](x: T)(implicit tag: TypeTag[T]): Boolean = PartialFunction.cond(tag.tpe) {
case SingleType(_, _) => true
}
object AnObject
case object ACaseObject
class AClass
case class ACaseClass(i: Int)
trait ATrait
println("new AClass " + isObject(new AClass))
println("ACaseClass(42) " + isObject(ACaseClass(42)))
println("new ATrait {} " + isObject(new ATrait {}))
println("AnObject " + isObject(AnObject))
println("ACaseObject " + isObject(ACaseObject))
}
Prints:
new AClass false
ACaseClass(42) false
new ATrait {} false
AnObject true
ACaseObject true
Depends on:
libraryDependencies += "org.scala-lang" % "scala-reflect" % scalaVersion.value
edited Nov 25 '18 at 8:50
Suma
21.6k891155
answered Nov 24 '18 at 9:03
ygorygor
1,111615
I hardcoded scala version into the dependency, which is quite wrong. Thanks @Suma for the edit ! Also edited: stackoverflow.com/questions/53326545/… and stackoverflow.com/questions/53391593/…
– ygor
Nov 25 '18 at 11:38
add a comment |
4
4
4
Using scala-reflect, following seems to work:
object ObjectReflection extends App {
import scala.reflect.runtime.universe._
def isObject[T](x: T)(implicit tag: TypeTag[T]): Boolean = PartialFunction.cond(tag.tpe) {
case SingleType(_, _) => true
}
object AnObject
case object ACaseObject
class AClass
case class ACaseClass(i: Int)
trait ATrait
println("new AClass " + isObject(new AClass))
println("ACaseClass(42) " + isObject(ACaseClass(42)))
println("new ATrait {} " + isObject(new ATrait {}))
println("AnObject " + isObject(AnObject))
println("ACaseObject " + isObject(ACaseObject))
}
Prints:
new AClass false
ACaseClass(42) false
new ATrait {} false
AnObject true
ACaseObject true
Depends on:
libraryDependencies += "org.scala-lang" % "scala-reflect" % scalaVersion.value
edited Nov 25 '18 at 8:50
Suma
21.6k891155
answered Nov 24 '18 at 9:03
ygorygor
1,111615
Using scala-reflect, following seems to work:
object ObjectReflection extends App {
import scala.reflect.runtime.universe._
def isObject[T](x: T)(implicit tag: TypeTag[T]): Boolean = PartialFunction.cond(tag.tpe) {
case SingleType(_, _) => true
}
object AnObject
case object ACaseObject
class AClass
case class ACaseClass(i: Int)
trait ATrait
println("new AClass " + isObject(new AClass))
println("ACaseClass(42) " + isObject(ACaseClass(42)))
println("new ATrait {} " + isObject(new ATrait {}))
println("AnObject " + isObject(AnObject))
println("ACaseObject " + isObject(ACaseObject))
}
Prints:
new AClass false
ACaseClass(42) false
new ATrait {} false
AnObject true
ACaseObject true
Depends on:
libraryDependencies += "org.scala-lang" % "scala-reflect" % scalaVersion.value
edited Nov 25 '18 at 8:50
Suma
21.6k891155
answered Nov 24 '18 at 9:03
ygorygor
1,111615
edited Nov 25 '18 at 8:50
Suma
21.6k891155
edited Nov 25 '18 at 8:50
Suma
21.6k891155
edited Nov 25 '18 at 8:50
Suma
21.6k891155
21.6k891155
answered Nov 24 '18 at 9:03
ygorygor
1,111615
answered Nov 24 '18 at 9:03
ygorygor
1,111615
answered Nov 24 '18 at 9:03
ygorygor
1,111615
1,111615
I hardcoded scala version into the dependency, which is quite wrong. Thanks @Suma for the edit ! Also edited: stackoverflow.com/questions/53326545/… and stackoverflow.com/questions/53391593/…
– ygor
Nov 25 '18 at 11:38
add a comment |
I hardcoded scala version into the dependency, which is quite wrong. Thanks @Suma for the edit ! Also edited: stackoverflow.com/questions/53326545/… and stackoverflow.com/questions/53391593/…
– ygor
Nov 25 '18 at 11:38
I hardcoded scala version into the dependency, which is quite wrong. Thanks @Suma for the edit ! Also edited: stackoverflow.com/questions/53326545/… and stackoverflow.com/questions/53391593/…
– ygor
Nov 25 '18 at 11:38
I hardcoded scala version into the dependency, which is quite wrong. Thanks @Suma for the edit ! Also edited: stackoverflow.com/questions/53326545/… and stackoverflow.com/questions/53391593/…
– ygor
Nov 25 '18 at 11:38
add a comment |
1
As a first approximation, you can do
def isObject(c: Class[_]): Boolean = c.getName.endsWith("$")
because the anonymous class created for a singleton object y has name y$, and the usual anonymous classes (such as new AnyRef {}) end in $<number> instead.
But it's legal to create class y$ as well, which would give a false positive; such names are rare in practice, though.
Using scala-reflect should allow a more precise answer.
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
107k25212353
add a comment |
1
As a first approximation, you can do
def isObject(c: Class[_]): Boolean = c.getName.endsWith("$")
because the anonymous class created for a singleton object y has name y$, and the usual anonymous classes (such as new AnyRef {}) end in $<number> instead.
But it's legal to create class y$ as well, which would give a false positive; such names are rare in practice, though.
Using scala-reflect should allow a more precise answer.
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
107k25212353
add a comment |
1
1
1
As a first approximation, you can do
def isObject(c: Class[_]): Boolean = c.getName.endsWith("$")
because the anonymous class created for a singleton object y has name y$, and the usual anonymous classes (such as new AnyRef {}) end in $<number> instead.
But it's legal to create class y$ as well, which would give a false positive; such names are rare in practice, though.
Using scala-reflect should allow a more precise answer.
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
107k25212353
As a first approximation, you can do
def isObject(c: Class[_]): Boolean = c.getName.endsWith("$")
because the anonymous class created for a singleton object y has name y$, and the usual anonymous classes (such as new AnyRef {}) end in $<number> instead.
But it's legal to create class y$ as well, which would give a false positive; such names are rare in practice, though.
Using scala-reflect should allow a more precise answer.
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
107k25212353
edited Nov 23 '18 at 19:03
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
107k25212353
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
107k25212353
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
107k25212353
107k25212353
add a comment |
add a comment |
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2
Why is this important for you? What difference is for you between
val obj = new Yorval obj = new AnyRef { }orobject obj {}?– Suma
Nov 23 '18 at 18:52
It's not important, just curiosity.
– jqno
Nov 25 '18 at 8:14