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How to get map of field names to field types of case class with shapeless
I browsed pretty much all tutorials and have "The Type Astronauts" on my desk but I still can't figure out how to write snippet which can extract map of names to types using shapeless from case class. To be precise I'm after following interface:
case class Sample(id: String, date: LocalDate)
def sampleExpectedMetadata = expectedMetadata[Sample] // = ("id" -> "String", "date" -> "LocalDate")
def expectedMetadata[T]: Map[String, String] = ???
Help from anyone who can assist with writing correct implementation would be greatly appreciated.
scala generic-programming shapeless
edited Nov 22 '18 at 15:58
Daniel Hinojosa
85458
asked Nov 22 '18 at 2:09
Petro SemeniukPetro Semeniuk
4,91533455
add a comment |
I browsed pretty much all tutorials and have "The Type Astronauts" on my desk but I still can't figure out how to write snippet which can extract map of names to types using shapeless from case class. To be precise I'm after following interface:
case class Sample(id: String, date: LocalDate)
def sampleExpectedMetadata = expectedMetadata[Sample] // = ("id" -> "String", "date" -> "LocalDate")
def expectedMetadata[T]: Map[String, String] = ???
Help from anyone who can assist with writing correct implementation would be greatly appreciated.
scala generic-programming shapeless
edited Nov 22 '18 at 15:58
Daniel Hinojosa
85458
asked Nov 22 '18 at 2:09
Petro SemeniukPetro Semeniuk
4,91533455
add a comment |
I browsed pretty much all tutorials and have "The Type Astronauts" on my desk but I still can't figure out how to write snippet which can extract map of names to types using shapeless from case class. To be precise I'm after following interface:
case class Sample(id: String, date: LocalDate)
def sampleExpectedMetadata = expectedMetadata[Sample] // = ("id" -> "String", "date" -> "LocalDate")
def expectedMetadata[T]: Map[String, String] = ???
Help from anyone who can assist with writing correct implementation would be greatly appreciated.
scala generic-programming shapeless
edited Nov 22 '18 at 15:58
Daniel Hinojosa
85458
asked Nov 22 '18 at 2:09
Petro SemeniukPetro Semeniuk
4,91533455
I browsed pretty much all tutorials and have "The Type Astronauts" on my desk but I still can't figure out how to write snippet which can extract map of names to types using shapeless from case class. To be precise I'm after following interface:
case class Sample(id: String, date: LocalDate)
def sampleExpectedMetadata = expectedMetadata[Sample] // = ("id" -> "String", "date" -> "LocalDate")
def expectedMetadata[T]: Map[String, String] = ???
Help from anyone who can assist with writing correct implementation would be greatly appreciated.
scala generic-programming shapeless
scala generic-programming shapeless
edited Nov 22 '18 at 15:58
Daniel Hinojosa
85458
asked Nov 22 '18 at 2:09
Petro SemeniukPetro Semeniuk
4,91533455
edited Nov 22 '18 at 15:58
Daniel Hinojosa
85458
asked Nov 22 '18 at 2:09
Petro SemeniukPetro Semeniuk
4,91533455
edited Nov 22 '18 at 15:58
Daniel Hinojosa
85458
edited Nov 22 '18 at 15:58
Daniel Hinojosa
85458
edited Nov 22 '18 at 15:58
Daniel Hinojosa
85458
85458
asked Nov 22 '18 at 2:09
Petro SemeniukPetro Semeniuk
4,91533455
asked Nov 22 '18 at 2:09
Petro SemeniukPetro Semeniuk
4,91533455
asked Nov 22 '18 at 2:09
Petro SemeniukPetro Semeniuk
4,91533455
4,91533455
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
I could be wrong that Shapeless would have nothing to do with this sort of introspection, using the answer from Get field names list from case class and refining it, your answer would be:
import scala.reflect.runtime.universe._
def expectedMetadata[T](implicit t:TypeTag[T]):Map[String, String] =
t.tpe.members
.collect { case m:MethodSymbol if m.isCaseAccessor => m }
.map(x => x.name.toString -> x.returnType.toString)
.toMap
Where, expectedMetadata[Sample] will return Map[String,String] = Map(date -> java.time.LocalDate, id -> String)
answered Nov 22 '18 at 16:56
Daniel HinojosaDaniel Hinojosa
85458
add a comment |
Did you have something like this in mind?
import shapeless._
import shapeless.record._
import shapeless.labelled._
object expectedMetadata {
def apply[T](implicit g: GetFieldTypes[T]): Map[String, String] = g.getFieldTypes
sealed trait GetFieldTypes[T] {
def getFieldTypes: Map[String,String]
}
implicit val hnil = new GetFieldTypes[HNil] {
def getFieldTypes = Map.empty
}
implicit def hcons[K <: Symbol, V, T <: HList](implicit
wit: Witness.Aux[K],
typ: Typeable[V],
rest: GetFieldTypes[T]
) = new GetFieldTypes[FieldType[K, V] :: T] {
def getFieldTypes = rest.getFieldTypes + (wit.value.name -> typ.describe)
}
implicit def caseClass[T, G](implicit
lg: LabelledGeneric.Aux[T, G],
rest: GetFieldTypes[G]
) = new GetFieldTypes[T] {
def getFieldTypes = rest.getFieldTypes
}
}
Sample use:
scala> case class Sample(id: String, date: LocalDate)
scala> expectedMetadata[Sample]
res1: Map[String,String] = Map(date -> LocalDate, id -> String)
answered Nov 22 '18 at 22:25
AlecAlec
24.6k44589
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
I could be wrong that Shapeless would have nothing to do with this sort of introspection, using the answer from Get field names list from case class and refining it, your answer would be:
import scala.reflect.runtime.universe._
def expectedMetadata[T](implicit t:TypeTag[T]):Map[String, String] =
t.tpe.members
.collect { case m:MethodSymbol if m.isCaseAccessor => m }
.map(x => x.name.toString -> x.returnType.toString)
.toMap
Where, expectedMetadata[Sample] will return Map[String,String] = Map(date -> java.time.LocalDate, id -> String)
answered Nov 22 '18 at 16:56
Daniel HinojosaDaniel Hinojosa
85458
add a comment |
I could be wrong that Shapeless would have nothing to do with this sort of introspection, using the answer from Get field names list from case class and refining it, your answer would be:
import scala.reflect.runtime.universe._
def expectedMetadata[T](implicit t:TypeTag[T]):Map[String, String] =
t.tpe.members
.collect { case m:MethodSymbol if m.isCaseAccessor => m }
.map(x => x.name.toString -> x.returnType.toString)
.toMap
Where, expectedMetadata[Sample] will return Map[String,String] = Map(date -> java.time.LocalDate, id -> String)
answered Nov 22 '18 at 16:56
Daniel HinojosaDaniel Hinojosa
85458
add a comment |
I could be wrong that Shapeless would have nothing to do with this sort of introspection, using the answer from Get field names list from case class and refining it, your answer would be:
import scala.reflect.runtime.universe._
def expectedMetadata[T](implicit t:TypeTag[T]):Map[String, String] =
t.tpe.members
.collect { case m:MethodSymbol if m.isCaseAccessor => m }
.map(x => x.name.toString -> x.returnType.toString)
.toMap
Where, expectedMetadata[Sample] will return Map[String,String] = Map(date -> java.time.LocalDate, id -> String)
answered Nov 22 '18 at 16:56
Daniel HinojosaDaniel Hinojosa
85458
I could be wrong that Shapeless would have nothing to do with this sort of introspection, using the answer from Get field names list from case class and refining it, your answer would be:
import scala.reflect.runtime.universe._
def expectedMetadata[T](implicit t:TypeTag[T]):Map[String, String] =
t.tpe.members
.collect { case m:MethodSymbol if m.isCaseAccessor => m }
.map(x => x.name.toString -> x.returnType.toString)
.toMap
Where, expectedMetadata[Sample] will return Map[String,String] = Map(date -> java.time.LocalDate, id -> String)
answered Nov 22 '18 at 16:56
Daniel HinojosaDaniel Hinojosa
85458
answered Nov 22 '18 at 16:56
Daniel HinojosaDaniel Hinojosa
85458
answered Nov 22 '18 at 16:56
Daniel HinojosaDaniel Hinojosa
85458
answered Nov 22 '18 at 16:56
Daniel HinojosaDaniel Hinojosa
85458
85458
add a comment |
add a comment |
Did you have something like this in mind?
import shapeless._
import shapeless.record._
import shapeless.labelled._
object expectedMetadata {
def apply[T](implicit g: GetFieldTypes[T]): Map[String, String] = g.getFieldTypes
sealed trait GetFieldTypes[T] {
def getFieldTypes: Map[String,String]
}
implicit val hnil = new GetFieldTypes[HNil] {
def getFieldTypes = Map.empty
}
implicit def hcons[K <: Symbol, V, T <: HList](implicit
wit: Witness.Aux[K],
typ: Typeable[V],
rest: GetFieldTypes[T]
) = new GetFieldTypes[FieldType[K, V] :: T] {
def getFieldTypes = rest.getFieldTypes + (wit.value.name -> typ.describe)
}
implicit def caseClass[T, G](implicit
lg: LabelledGeneric.Aux[T, G],
rest: GetFieldTypes[G]
) = new GetFieldTypes[T] {
def getFieldTypes = rest.getFieldTypes
}
}
Sample use:
scala> case class Sample(id: String, date: LocalDate)
scala> expectedMetadata[Sample]
res1: Map[String,String] = Map(date -> LocalDate, id -> String)
answered Nov 22 '18 at 22:25
AlecAlec
24.6k44589
add a comment |
Did you have something like this in mind?
import shapeless._
import shapeless.record._
import shapeless.labelled._
object expectedMetadata {
def apply[T](implicit g: GetFieldTypes[T]): Map[String, String] = g.getFieldTypes
sealed trait GetFieldTypes[T] {
def getFieldTypes: Map[String,String]
}
implicit val hnil = new GetFieldTypes[HNil] {
def getFieldTypes = Map.empty
}
implicit def hcons[K <: Symbol, V, T <: HList](implicit
wit: Witness.Aux[K],
typ: Typeable[V],
rest: GetFieldTypes[T]
) = new GetFieldTypes[FieldType[K, V] :: T] {
def getFieldTypes = rest.getFieldTypes + (wit.value.name -> typ.describe)
}
implicit def caseClass[T, G](implicit
lg: LabelledGeneric.Aux[T, G],
rest: GetFieldTypes[G]
) = new GetFieldTypes[T] {
def getFieldTypes = rest.getFieldTypes
}
}
Sample use:
scala> case class Sample(id: String, date: LocalDate)
scala> expectedMetadata[Sample]
res1: Map[String,String] = Map(date -> LocalDate, id -> String)
answered Nov 22 '18 at 22:25
AlecAlec
24.6k44589
add a comment |
Did you have something like this in mind?
import shapeless._
import shapeless.record._
import shapeless.labelled._
object expectedMetadata {
def apply[T](implicit g: GetFieldTypes[T]): Map[String, String] = g.getFieldTypes
sealed trait GetFieldTypes[T] {
def getFieldTypes: Map[String,String]
}
implicit val hnil = new GetFieldTypes[HNil] {
def getFieldTypes = Map.empty
}
implicit def hcons[K <: Symbol, V, T <: HList](implicit
wit: Witness.Aux[K],
typ: Typeable[V],
rest: GetFieldTypes[T]
) = new GetFieldTypes[FieldType[K, V] :: T] {
def getFieldTypes = rest.getFieldTypes + (wit.value.name -> typ.describe)
}
implicit def caseClass[T, G](implicit
lg: LabelledGeneric.Aux[T, G],
rest: GetFieldTypes[G]
) = new GetFieldTypes[T] {
def getFieldTypes = rest.getFieldTypes
}
}
Sample use:
scala> case class Sample(id: String, date: LocalDate)
scala> expectedMetadata[Sample]
res1: Map[String,String] = Map(date -> LocalDate, id -> String)
answered Nov 22 '18 at 22:25
AlecAlec
24.6k44589
Did you have something like this in mind?
import shapeless._
import shapeless.record._
import shapeless.labelled._
object expectedMetadata {
def apply[T](implicit g: GetFieldTypes[T]): Map[String, String] = g.getFieldTypes
sealed trait GetFieldTypes[T] {
def getFieldTypes: Map[String,String]
}
implicit val hnil = new GetFieldTypes[HNil] {
def getFieldTypes = Map.empty
}
implicit def hcons[K <: Symbol, V, T <: HList](implicit
wit: Witness.Aux[K],
typ: Typeable[V],
rest: GetFieldTypes[T]
) = new GetFieldTypes[FieldType[K, V] :: T] {
def getFieldTypes = rest.getFieldTypes + (wit.value.name -> typ.describe)
}
implicit def caseClass[T, G](implicit
lg: LabelledGeneric.Aux[T, G],
rest: GetFieldTypes[G]
) = new GetFieldTypes[T] {
def getFieldTypes = rest.getFieldTypes
}
}
Sample use:
scala> case class Sample(id: String, date: LocalDate)
scala> expectedMetadata[Sample]
res1: Map[String,String] = Map(date -> LocalDate, id -> String)
answered Nov 22 '18 at 22:25
AlecAlec
24.6k44589
answered Nov 22 '18 at 22:25
AlecAlec
24.6k44589
answered Nov 22 '18 at 22:25
AlecAlec
24.6k44589
answered Nov 22 '18 at 22:25
AlecAlec
24.6k44589
24.6k44589
add a comment |
add a comment |
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