Scala merge list of maps - scala

Question

Input =
val data = List(
Map("id" -> "123", "name" -> "raju",
"sub" -> List(Map("id" -> "english", "status" -> 2))),
Map("id" -> "123", "name" -> "raju",
"sub" -> List(Map("id" -> "english", "status" -> 0),
Map("id" -> "hindi", "status" -> 0))))
Expected Output:
val data = List(
Map("id" -> "123", "name" -> "raju",
"sub" -> List(Map("id" -> "english", "status" -> 2),
Map("id" -> "hindi", "status" -> 1),
Map("id" -> "english", "status" -> 0),
Map("id" -> "hindi", "status" -> 0))))
I'm trying to merge the "sub" key values into a list without removing the old keys but I couldn't able to get it. can anyone please help with this using scala.

Answer 1

Start by creating some case classes. It is much easier to work with these than with maps.
case class Person(id: String, name: String, sub: List[Language])
case class Language(id: String, status: Int)
Now, create a list of Person:
val data = List(
Person("123", "raju", List(Language("english", 2))),
Person("123", "raju", List(Language("english", 0), Language("hindi", 0))))
I don't know what your merging logic is, but let's say you just want to concatenate the sub-lists for persons with the same ID. You could do it this way:
// Gets a map from ID to the list of persons with that ID
data.groupBy(_.id)
// Gets a List[List[Person]] (the values of the map)
.values
// Makes a new Person out of the inner list of persons, concatenating all the languages of that person.
.map(persons => Person(
persons.head.id,
persons.head.name,
persons.flatMap(_.sub)))

Answer 2

Here is example that works on pure Maps/Lists like in your example.
val data = List(
Map("id" -> "123", "name" -> "raju",
"sub" -> List(Map("id" -> "english", "status" -> 2))),
Map("id" -> "123", "name" -> "raju",
"sub" -> List(Map("id" -> "english", "status" -> 0),
Map("id" -> "hindi", "status" -> 0))))
val expected = List(
Map("id" -> "123", "name" -> "raju",
"sub" -> List(Map("id" -> "english", "status" -> 2),
Map("id" -> "hindi", "status" -> 1),
Map("id" -> "english", "status" -> 0),
Map("id" -> "hindi", "status" -> 0))))
val res = data.groupBy(x => (x.get("id"), x.get("name"))).collect { case (_, items) =>
items.reduceLeft { (l, r) =>
l.updated("sub", l("sub").asInstanceOf[List[_]] ++ r("sub").asInstanceOf[List[_]])
}
}
println(res)
https://scalafiddle.io/sf/FBj4Mvi/0
PS: To be honest creating typed structure (as proposed by others) is probably still better sollution.