How to add an additional json item per object in scala - json

Question

I'm writing a simple scala application that opens a flat file of json data, parses it and finally prints it out to the screen.
The next step will require that I stop at each object and add another item (string) to the front of it. My question is how can I add a new string per object in this list?
The following is my JSON implementation (credit goes to the init author here)
import scala.util.parsing.combinator._
class JSON extends JavaTokenParsers {
def obj: Parser[Map[String, Any]] =
"{"~> repsep(member, ",") <~"}" ^^ (Map() ++ _)
def arr: Parser[List[Any]] =
"["~> repsep(value, ",") <~"]"
def member: Parser[(String, Any)] =
stringLiteral~":"~value ^^
{ case name~":"~value => (name, value) }
def value: Parser[Any] = (
obj
| arr
| stringLiteral
| floatingPointNumber ^^ (_.toInt)
| "null" ^^ (x => null)
| "true" ^^ (x => true)
| "false" ^^ (x => false)
)
}
Next I call this w/ a flat file like so
import java.io.FileReader
import scala23.JSON
class JSONTest extends JSON {
def main(args: String) {
val reader = new FileReader(args)
println(parseAll(value, reader))
}
}
Then I get a valid println of the json contents. Instead I would like to pass this parse method a String and have it append it or create a new json object that has the string at the front of each object inside
Update
My current attempt looks something like the below
class JSONTest extends JSON {
def main(args: String) {
val reader = new FileReader(args)
val header = ("abc", "def")
// println(parseAll(value, reader).map(addHeader(_, header)))
println(parseAll(value, reader).map(addHeader(_.asInstanceOf[Map[String, Any]], header)))
}
def addHeader(xyz:Map[String, Any], header:(String, Any)):Map[String, Any] = {
xyz.map {
case (k, m:Map[String, Any]) => (k, addHeader(m))
case e => e
} + header
}
}
But I'm currently getting a few errors in Intellij
error: missing parameter type for expanded function ((x$1) => x$1.asInstanceOf[Map[String, Any]])
println(parseAll(value, reader).map(addHeader(_.asInstanceOf[Map[String, Any]], header)))
AND
error: not enough arguments for method addHeader: (xyz: Map[String,Any],header: (String, Any))Map[String,Any].
Unspecified value parameter header.
case (k, m:Map[String, Any]) => (k, addHeader(m))
Any help would be much appreciated (thank you in advance!)

Answer 1

Have you tried using map on the parser output instead.
Edit: this compiles on my machine
import java.io.FileReader
import scala23.JSON
class JSONTest extends JSON {
def main(args: String) {
val reader = new FileReader(args)
val header = ("abc", "def")
// println(parseAll(value, reader).map(addHeader(_, header)))
println(parseAll(value, reader).map(addHeader(_, header)))
}
def addHeader(xyz:Any, header:(String, Any)):Any = xyz match {
case obj:Map[String, Any] => obj.map {
case (k, m:Map[String, Any]) => (k, addHeader(m, header))
case e => e
} + header
case arr:List[Any] => arr.map(addHeader(_, header))
case e => e
}
}
It should be handling the varied output of the parse better.