I have a list
w: List[Any] = List(A, B, C)
i want to dynamically create a variable
for (e <- w) {
//val $e = notebook.filter(s"Name='$e'").select("Location")
println(e)
}
so three variables A,B,C should be created with their corresponding location values.
Any help is appreciated thank you
You can create a list of variables
val List(e1, e2, e3) = w.map { e =>
println(e)
notebook.filter(s"Name='$e'").select("Location")
}
or
val es = w.map { e =>
println(e)
notebook.filter(s"Name='$e'").select("Location")
}
and use variables (vals) e1, e2, e3 or es(0), es(1), es(2).
i want the variable to have the same value as name. I would want to use tht variables in other part of the code
Then you can use a macro annotation
import scala.annotation.{StaticAnnotation, compileTimeOnly}
import scala.language.experimental.macros
import scala.reflect.macros.blackbox
@compileTimeOnly("enable macro annotations")
class generateVariables(names: String*) extends StaticAnnotation {
def macroTransform(annottees: Any*): Any = macro GenerateVariablesMacro.impl
}
object GenerateVariablesMacro {
def impl(c: blackbox.Context)(annottees: c.Tree*): c.Tree = {
import c.universe._
val names = c.prefix.tree match {
case q"new generateVariables(..$ns)" => ns
}
val variables = names.map { case q"${name: String}" =>
q"""val ${TermName(name)} = notebook.filter(${s"Name='$name'"}).select("Location")"""
}
annottees match {
case q"$mods object $tname extends { ..$earlydefns } with ..$parents { $self => ..$body }" :: Nil =>
q"""$mods object $tname extends { ..$earlydefns } with ..$parents { $self =>
..$variables
..$body
}"""
}
}
}
Usage:
@generateVariables("A", "B", "C")
object X
//scalac: object X extends scala.AnyRef {
// def <init>() = {
// super.<init>();
// ()
// };
// val A = notebook.filter("Name=\'A\'").select("Location");
// val B = notebook.filter("Name=\'B\'").select("Location");
// val C = notebook.filter("Name=\'C\'").select("Location")
//}
Now you can use variables X.A, X.B, X.C (or if you import X._ then just A, B, C).
