How to delete key from Map in Option Scala - scala

Question

Say i have case classes like this.
case class someClass0(content: someClass1)
case class someClass1(someContent: Option[Map[String, someClass2]])
case class someClass2(someKey: Array[Int])
I need to delete items in Map(which is immutable) by values.
This values i get through iteration.
val keys_to_remove = new ListBuffer[String]()
val keys_to_keep: List[Int] = List(100, 200)
for (x <- keys_to_keep) {
content.someContent.get.foreach {
case (key: String, value: someClass2) => {
if (!value.someKey.contains(x)) {
keys_to_remove.append(key)
}
}
}
}
So, how to keep all the structure, and delete only needed items by key?
I was trying to change type of Map like
content.someContent.map(_.to(collection.mutable.Map))
But content.someContent.get.remove(key) is not working.
What am i doing wrong?

Answer 1

You don't need mutability for that.
val keys_to_keep: List[String] = List("a", "b")
val res = content.someContent.map(
_.filterKeys(k => !keys_to_keep.contains(k))
)
filterKeys filters a Map by testing each entries' key against a condition.
Of course, it is important to remember that you can't test contains on a List[Int] against Strings, as the result will always be false.
Furthermore, try looking up style-guides for Scala:
Classes are usually named in upper camel case
Values and variables are usually named in lower camel case
Try it out

Answer 2

You can do it using - operator and foldLeft on keys to remove.
you are using get for get value, if you want do it safety, you need to use:
content.someContent.map(immutableMap =>
keys_to_remove.foldLeft(immutableMap){
(map, key) =>
map - key
}).getOrElse(Map.empty[String, SomeClass2])
this works like in this example:
import scala.collection.mutable.ListBuffer
val immutableMap = Map("a" -> 1, "b" -> 2, "c" -> 3, "d" -> 4)
val keys_to_remove: ListBuffer[String] = ListBuffer("b", "d")
println(immutableMap) // Map(a -> 1, b -> 2, c -> 3, d -> 4)
val mapWithoutKeys = keys_to_remove.foldLeft(immutableMap){
(map, key) =>
map - key
}
println(mapWithoutKeys) //Map(a -> 1, c -> 3)

Answer 3

Here's how you can do it:
val optionalMap = someClass0.content.someContent.map {
contentMap => contentMap - keyToBeRemoved
}
val originalStructure = someClass0.copy(content = SomeClass1(optionalMap))
Here's the Scastie

Answer 4

This will remove all keys and keep structure
val someClass0_copy = someClass0.copy(content = Content(someContent = someClass0.content. someContent.map(_.removedAll(keysToRemove)))