Scala Print Map in Order

Question

I have a Map[String,String] and I would like to print it in a particular order depending on the keys. For example I would like to print the value of id, name, address. So I would like to match my keys to "id","name", "address" and then print the values at each of these keys. I have the following code but it doesn't work:

articlesmap.keys match{
    case ("id") => println(articlesmap.get("id"))
        case ("name") => println(articlesmap.get("name"))
        case ("address") => println(articlesmap.get("address"))
 }

why pattern matching? why not just the println statements? — Karthik T
– Karthik T, Commented Feb 8, 2013 at 5:28
I find really useful what @nimda pointed out. Regardless of alternative solutions, you're trying to match on the keys of the map, which is a Iterator[String]; that is the exact reason you're not getting the expected result. — pagoda_5b
– pagoda_5b, Commented Feb 8, 2013 at 7:33

Faiz · Accepted Answer · 2013-02-08 11:25:30Z

7

You could use for:

for { 
  k <- Seq("id", "name", "address") // the keys in the order you want to print them.
  v <- articlesmap.get(k) 
} println (k+ " is " + v)

If you just want to print values, collect will do fine:

Seq("id", "name", "address") collect articlesmap foreach println

collect is better than map id you can't be certain that a key is actually in the map.

edited Feb 8, 2013 at 11:25

answered Feb 8, 2013 at 5:42

Faiz

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Comments

Sergey Passichenko · Accepted Answer · 2013-02-08 06:14:27Z

3

here is the simplest solution as I know:

scala>  val keys = Seq("id", "name", "address") 
keys: Seq[java.lang.String] = List(id, name, address)

scala>  val articlesmap = Map("id" -> 1, "name" -> "john", "address" -> "some address")
articlesmap: scala.collection.immutable.Map[java.lang.String,Any] = Map(id -> 1, name -> john, address -> some address)

scala>  keys map articlesmap foreach println
1
john
some address

scala>  val keys = Seq("name", "id", "address")
keys: Seq[java.lang.String] = List(name, id, address)

scala>  keys map articlesmap foreach println
john
1
some address

answered Feb 8, 2013 at 6:14

Sergey Passichenko

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Comments

nimda · Accepted Answer · 2013-02-08 05:41:15Z

2

Variable articlesmap.keys is of type Iterable[String], but your case matches are matching on type String. Try this instead:

def mapTest(map: Map[String, String]) {
    map.keys.foreach {
      case ("id") => println(map.get("id"))
      case ("name") => println(map.get("name"))
      case ("address") => println(map.get("address"))
    }
  }                                            

  val mapper = Map("id" -> "123", "name" -> "Bob", "address" -> "123 Fake Street")

  mapTest(mapper)

  // => Some(123)
  //    Some(Bob)
  //    Some(123 Fake Street)

answered Feb 8, 2013 at 5:41

nimda

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1 Comment

princess of persia Over a year ago

The order is not what I want, the order is what is in the map hence the purpose is defeated, I would like to print it in the order I want.

Randall Schulz · Accepted Answer · 2013-02-08 05:47:12Z

2

You could create an OrderedMap or you could sort the keys and process the result of that sort.

answered Feb 8, 2013 at 5:47

Randall Schulz

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