Scala Map foreach

Solution 1:

I'm not sure about the error, but you can achieve what you want as follows:

m.foreach(p => println(">>> key=" + p._1 + ", value=" + p._2))

That is, foreach takes a function that takes a pair and returns Unit, not a function that takes two arguments: here, p has type (String, Int).

Another way to write it is:

m.foreach { case (key, value) => println(">>> key=" + key + ", value=" + value) }

In this case, the { case ... } block is a partial function.

Solution 2:

oops, read the doco wrong, map.foreach expects a function literal with a tuple argument!

so

m.foreach((e: (String, Int)) => println(e._1 + "=" + e._2))

works

Solution 3:

You need to patter-match on the Tuple2 argument to assign variables to its subparts key, value. You can do with very few changes:

m.foreach{ case (key: String, value: Int) => println(">>> key=" + key + ", value=" + value)} 

Solution 4:

The confusing error message is a compiler bug, which should be fixed in 2.9.2: