how to access key values within nested map in Scala - scala

Question

I have a List of Maps. One of the maps has another map inside it (2 level deep). I need to access some of keys from the inner most map and finally change the values. The issue I'm facing is to retrieve the keys from the inner most map. I'm very new to Scala and tried different things without luck.
I have flatten the List to Map and then tried to retrieve the key, values. The thing is, I can print the entire inner map, but not sure how to iterate thru that.
Below is the code: at a very basic, I would like to retrieve the values corresponding to keys from innermost map; say for the keys "isStudentLoankRequested", "schoolStructure".
object ListToMaps {
def main(args: Array[String]) {
val dataInputKeysListvar = List(Map("identityKeyName" -> "MY_ID", "identityKeyValue" -> "abcd-1234-xyz"),
Map("identityKeyName" -> "OUR_ID", "identityKeyValue" -> "1234567890",
"identityInformation" -> Map("writeFrequency" -> "NEVER", "studentStatus" -> "SEP", "annualValue" -> 0,
"schoolStructure" -> "OTHER", "studentType" -> "FTS", "occupationDescription" -> "other",
"studentAccountBalanceRange" -> "string", "isStudentLoankRequested" -> "N", "schoolName" -> "myschool",
"parentsIncome" -> 100)),
Map("identityKeyName" -> "FINAL_DECISION_KEY", "identityKeyValue" -> "0000-ABCD-4567-IJKL"))
val x = dataInputKeysListvar.flatten.toMap
val y = x("identityInformation")
if (x.contains("identityInformation")){
println("value of y is" + y)
}
}
}
As you can see from the print stmt, I can print the entire map of the inner most map, but need help in terms of iterating thru that.

Answer 1

If you know at compile time which fields and values you need to change.
You can hard code the logic, like this:
def fixData(data: List[Map[String, Any]]): List[Map[String, Any]] =
data.map { outerMap =>
outerMap.get("identityInformation") match {
case Some(innerMap) =>
// Put as many key pairs you want to change.
// Note: if the key does not exists it will be added!
val updatedInnerMap = innerMap.asInstanceOf[Map[String, String]] ++ Map(
"isStudentLoankRequested" -> "No"
)
outerMap + ("identityInformation" -> updatedInnerMap)
case None =>
outerMap
}
}
If the key-values to change are dynamic, and / or some inner keys may not exists, or if the level of nesting can go on.
You can do something like this:
def updateMap(map: Map[String, Any], updates: Map[String, Any]): Map[String, Any] =
map.map {
case (key, value: Map[_, _]) =>
updates.get(key) match {
case Some(innerUpdates : Map[_, _]) =>
key -> updateMap(
map = value.asInstanceOf[Map[String, Any]],
updates = innerUpdates.asInstanceOf[Map[String, Any]]
)
case Some(newValue) =>
key -> newValue
case None =>
key -> value
}
case (key, value) =>
key -> updates.getOrElse(key, default = value)
}
def fixData(data: List[Map[String, Any]], updates: Map[String, Any]): List[Map[String, Any]] =
data.map(outerMap => updateMap(outerMap, updates))
Note: The above snippets use "unsafe" techniques like asInstanceOf because we lost type safety the moment you got a Map[String, Any]. Always that I see such structure, I think of JSON. I would suggest you to use an appropriate library for managing such kind of data, like circe, instead of writing code as the above.