How to iterate scala map?

Question

I have scala map:

attrs: Map[String , String] 

When I try to iterate over map like;

attrs.foreach { key, value =>     } 

the above does not work. In each iteration I must know what is the key and what is the value. What is the proper way to iterate over scala map using scala syntactic sugar?

Answer 1

Three options:

attrs.foreach( kv => ... )          // kv._1 is the key, kv._2 is the value attrs.foreach{ case (k,v) => ... }  // k is the key, v is the value for ((k,v) <- attrs) { ... }        // k is the key, v is the value 

The trick is that iteration gives you key-value pairs, which you can't split up into a key and value identifier name without either using case or for.

Answer 2

foreach method receives Tuple2[String, String] as argument, not 2 arguments. So you can either use it like tuple:

attrs.foreach {keyVal => println(keyVal._1 + "=" + keyVal._2)} 

or you can make pattern match:

attrs.foreach {case(key, value) => ...}