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
11.1k64766
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
11.1k64766
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
11.1k64766
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
11.1k64766
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64766
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64766
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64766
asked Nov 23 '18 at 12:57
jqnojqno
11.1k64766
11.1k64766
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
21.5k890155
answered Nov 24 '18 at 9:03
ygorygor
1,088615
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
106k25209350
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
draft saved
draft discarded
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53447160%2fscala-reflection-can-i-see-if-something-is-a-case-object%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
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
21.5k890155
answered Nov 24 '18 at 9:03
ygorygor
1,088615
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
21.5k890155
answered Nov 24 '18 at 9:03
ygorygor
1,088615
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
21.5k890155
answered Nov 24 '18 at 9:03
ygorygor
1,088615
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
21.5k890155
answered Nov 24 '18 at 9:03
ygorygor
1,088615
edited Nov 25 '18 at 8:50
Suma
21.5k890155
edited Nov 25 '18 at 8:50
Suma
21.5k890155
edited Nov 25 '18 at 8:50
Suma
21.5k890155
21.5k890155
answered Nov 24 '18 at 9:03
ygorygor
1,088615
answered Nov 24 '18 at 9:03
ygorygor
1,088615
answered Nov 24 '18 at 9:03
ygorygor
1,088615
1,088615
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
106k25209350
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
106k25209350
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
106k25209350
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
106k25209350
edited Nov 23 '18 at 19:03
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
106k25209350
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
106k25209350
answered Nov 23 '18 at 18:49
Alexey RomanovAlexey Romanov
106k25209350
106k25209350
add a comment |
add a comment |
draft saved
draft discarded
Thanks for contributing an answer to Stack Overflow!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
draft saved
draft discarded
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53447160%2fscala-reflection-can-i-see-if-something-is-a-case-object%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
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