Vfrdtyky

Suppose I have a normalized database model for a generic type that comes in like this:

case class BaseModel(id: String, 

                     createdBy: String,

                     attr1: Option[String] = None,

                     attr2: Option[Int] = None, 

                     attr3: Option[LocalDate] = None)

Given a sequence of BaseModel, if all the fields of a certain Option attribute are not populated, can shapeless create a reduced model for me?

For example suppose that all the attr1 fields are empty. Without me having to specify the object before hand can shapeless create a generic object that looks like this?

case class BaseModel(id: String, 

                     createdBy: String,

                     attr2: Option[Int] = None, 

                     attr3: Option[LocalDate] = None)

What Shapeless can do is, given two case classes, create an object of one of them from an object of another.

import java.time.LocalDate

import shapeless.LabelledGeneric

import shapeless.record._



case class BaseModel(id: String,

                     createdBy: String,

                     attr1: Option[String] = None,

                     attr2: Option[Int] = None,

                     attr3: Option[LocalDate] = None)



case class BaseModel1(id: String,

                      createdBy: String,

                      attr2: Option[Int] = None,

                      attr3: Option[LocalDate] = None)



val bm = BaseModel(

  id = "cff4545gvgf", 

  createdBy = "John Doe", 

  attr2 = Some(42), 

  attr3 = Some(LocalDate.parse("2018-11-03"))

)  // BaseModel(cff4545gvgf,John Doe,None,Some(42),Some(2018-11-03))

val hlist = LabelledGeneric[BaseModel].to(bm)

val hlist1 = hlist - 'attr1

val bm1 = LabelledGeneric[BaseModel1].from(hlist1)    

   // BaseModel1(cff4545gvgf,John Doe,Some(42),Some(2018-11-03))

But Shapeless can't create a new case class. If you need a new case class to be created automatically you can write a macro.