In Scala 2.10, a new reflection library was introduced to add a more powerful toolkit of general reflective capabilities to Scala. Along with full-featured runtime reflection for Scala types and generics, Scala 2.10 also ships with compile-time reflection capabilities, in the form of macros, as well as the ability to reify Scala expressions into abstract syntax trees.
Questions tagged [scala-reflect]
278 questions
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1 answer
Scala accessing members of runtime types using reflection of a class that extends a trait
Suppose I have a MyItem trait and its companion object has an apply() function that creates a class instance called SubItem that extends from MyItem:
import scala.reflect.runtime.{universe => ru}
trait MyItem {
import MyItem._
def num:…
Hush
- 13
- 2
1
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1 answer
How to access scala annotation in scala code
I have defined a simple scala annoation and use it to annotate my case class Person:
package com.my
import scala.annotation.StaticAnnotation
@scala.annotation.meta.field
class Description(value: String) extends StaticAnnotation{
}
Then I use it…
Tom
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2 answers
How to call Databricks dbutils using Scala Reflection / Mirrors
I want to call
com.databricks.dbutils_v1.DBUtilsHolder.dbutils.secrets.get(scope = "myScope", key = "myKey")
using mirroring.
So far I achieve this:
val className = "com.databricks.dbutils_v1.DBUtilsHolder"
import scala.reflect.runtime.{universe…
Horscht310
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1 answer
Write method to a class dynamically at runtime in scala and create a jar
I would like to understand is there a way to write a method to existing class at runtime and to create a jar dynamically in scala.
So far i tried to create a class dynamically and able to run it thru reflection, however the class is dynamic class…
user3569397
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1 answer
Scala invoke Object apply method using string
I have a class MyFilter which has many different versions. Depending on the input version, I want to invoke that object and apply that filter. Sample is shown below:
object v1{
def apply(l: List[String]) = {
l.filter(_.contains("v1"))
…
Waqar Ahmed
- 5,005
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2 answers
Scala reflection to get List field value by universe apply
I defined an annotation class with a List field in Scala:
class TestAnnotation(a: String, b: List[String]) extends StaticAnnotation
And some classes using the annotation, e.g.:
@TestAnnotation("test", List("b1", "b2"))
class TestA
Now I want to…
W.Bing
- 11
- 1
1
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2 answers
How to get the declaring class / trait using Scala reflection?
Using Java reflection, I can make:
MyObject
.getClass
.getMethods
.map(_.getDeclaringClass())
For each method declared in the Object MyObject, I will get the declaring class of that method / value - what I'm interest here is, specifically, in…
Lucas Lima
- 832
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1 answer
Scala: verify class parameter is not instanceOf a trait at compile time
At compile time I want to verify that a class parameter is NOT an instance of a particular trait T. I know how to do it at runtime using require or a case match but wondering how this might be done at compile to prevent users from providing certain…
bawejakunal
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Scala equivalent of Java `Class` class?
In Java, there is a Class class that represents, well, classes. It's useful when you need to do some class checks dynamically at runtime, for example, if some interface can accept varied number of arguments and it expects the arguments to have…
siledh
- 3,268
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2 answers
How to get underlying constant type from singleton type with Scala reflection API
import scala.reflect.runtime.universe._
val a: 42 = 42
val t: Type = typeOf[a.type]
assert(getConstantType(t).get =:= typeOf[42])
def getConstantType(t: Type): Option[ConstantType] = ???
How could I generally implement getConstantType so that the…
user3773003
- 101
- 6
1
vote
1 answer
Changing Return type of a function in Scala
I need to write a function that has the return type NodeSeq (scala.xml.NodeSeq),
In the below function, I'm trying to get the NodeSeq of an XML file, by evaluating an expression using the below code. The compiler throws type mismatch error.
import…
chqdrian
- 335
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1 answer
WeakTypeOf from type parameter
I have a simple code with function which gets weakTypeOf case class and returns its fields, predictably we get 2 items list
def getMembers[T: WeakTypeTag] =
weakTypeOf[T].members.filterNot(_.isMethod).toList
final case class Person(name: String,…
Dmitry Reutov
- 2,995
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In scala 2.12, why none of the TypeTag created in runtime is serializable?
I'm seeking a method to create a serializable TypeTag without using compile time tools (completely relying on runtime). This is a basic feature for all reflective language.
The answer in this post proposed a few methods:
In Scala, how to create a…
tribbloid
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1 answer
In scala, how to create a ClassTag of a specialised class using ClassTag of its generic member?
Let's use the common Array[T] class as an example:
import scala.reflect.ClassTag
{
val t = implicitly[ClassTag[String]]
val ts = implicitly[ClassTag[Array[String]]]
Seq(t, ts).foreach(println)
}
this will give the following…
tribbloid
- 4,026
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- 103
1
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1 answer
Instantiating an empty object of parametric type
I'm trying to make a CSV reader that parse a CSV file with a header into a list of "line object". Those "line objects" are of a type given by the caller of the function.
The idea is to be able to use the CSV reader like that:
case class…
nefas
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