CODEWITHSUNDEEP
scala
KingFish
KingFish

Reputation: 9183

Creating a Map of a Map

I'm very new to Scala so I apologize for asking stupid questions. I'm coming from scripting languages such as python, perl, etc. that let you get away w/ a lot.

How do I create a map which contains a map? In Python, I can create the following:

{ 'key': { 'data': 'value' }}

...or in perl

%hash = ( 'key' => ( 'data' => 'value' ));

Also, what is the difference between Map and scala.collection.mutable/immutable.Map, or is there a difference?

Upvotes: 1

Views: 177

Answers (2)

Kim Stebel
Kim Stebel

Reputation: 42045

A slightly more simple way to create a map of maps:

Map("german"  -> Map(1 -> "eins", 2 -> "two"),
    "english" -> Map(1 -> "one",  2 -> "two"))

This way you do not have to specify the type explicitly. Regarding the difference between immutable and mutable: Once you have created an immutable map, you cannot change it. You can only create a new map based on the old one with some of the elements changed.

Upvotes: 3

tgr
tgr

Reputation: 3608

In scala you can create a Map, if you want to fill it at creation, this way:

val mapa = Map(key1 -> value1, key2 -> value2)

Another way would be:

var mapb = Map[Key, Value]()
mapb += key1 -> value1

A map of maps could be created this way:

var mapOfMaps = Map[String, Map[Int, String]]()
mapOfMaps += ("english" -> Map(1 -> "one", 2 -> "two"))
mapOfMaps += ("french" -> Map(1 -> "un", 2 -> "deux"))
mapOfMaps += ("german" -> Map(1 -> "eins", 2 -> "zwei"))

Note that the inner Map is immutable in this example.

Upvotes: 1

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