Scala how to convert Array[Map[String,String]] to Map[String, Map[String,String]]

Question

I have string of columns and they are grouped by they purpose etc address cols and personal info cols. val columns="address:addressLine,address:city,address:state,address:zipCode,person:firstName,person:lastName,person:middleName"

I wanted them to be arranged like that:

lastName->person,zipCode->address

So every pair like lastName->person would be a Map. I wanted these Maps to be placed inside another Map, like that:

columnSchema -> {
lastName->person,
zipCode->address
}

So it would be Map[String,Map[String,String]]

I started by doing it like that:

columns.split(",").map(_.split(":")).map(x=>Map(x(1)->x(0)))

What I got is:

Array[scala.collection.immutable.Map[String,String]] = Array(Map(addressLine -> address), Map(city -> address), Map(state -> address), Map(zipCode -> address), Map(firstName -> person), Map(lastName -> person), Map(middleName -> person))

So I got an Array[Map[String,String]]. How could I make it a Map[String,Map[String,String]]? I tried to do it like:

Map("columnSchema" -> columns.split(",").map(_.split(":")).map(x=>Map(x(1)->x(0))))

However it still returns an array of Maps:

scala.collection.immutable.Map[String,Array[scala.collection.immutable.Map[String,String]]]

How to get rid of an Array? Thanks!

Brian · Accepted Answer · 2021-04-29 23:01:00Z

2

Similar to what you have except add in toMap to convert the Array of tuples to a Map

Map("columnSchema" -> columns.split(",").map(_.split(":")).map(as => as(1) -> as(0)).toMap)

Returns:

Map[String, Map[String, String]] = 
Map(columnSchema -> 
  HashMap(city -> address,
          middleName -> person,
          state -> address,
          addressLine -> address,
          zipCode -> address,
          lastName -> person,
          firstName -> person)
)

answered Apr 29, 2021 at 23:01

Brian

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The fourth bird · Accepted Answer · 2021-04-29 23:59:57Z

Another option could be splitting on : or , using a character class [,:] and then group the result in collections of 2 and map using a partial function.

val res: Map[String, Map[String, String]] = Map(
  "columnSchema" -> 
    columns.split("[,:]").grouped(2)
    .map { case Array(k, v) => v -> k }.toMap
)

Output

Map(
columnSchema -> Map(
    city -> address,
    middleName -> person,
    state -> address,
    addressLine -> address,
    zipCode -> address,
    lastName -> person,
    firstName -> person
    )
)

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