Looping through a list of tuples in Scala - scala

Question

I have a sample List as below
List[(String, Object)]
How can I loop through this list using for?
I want to do something like
for(str <- strlist)
but for the 2d list above. What would be placeholder for str?

Answer 1

Here it is,
scala> val fruits: List[(Int, String)] = List((1, "apple"), (2, "orange"))
fruits: List[(Int, String)] = List((1,apple), (2,orange))
scala>
scala> fruits.foreach {
| case (id, name) => {
| println(s"$id is $name")
| }
| }
1 is apple
2 is orange
Note: The expected type requires a one-argument function accepting a 2-Tuple.
Consider a pattern matching anonymous function, { case (id, name) => ... }
Easy to copy code:
val fruits: List[(Int, String)] = List((1, "apple"), (2, "orange"))
fruits.foreach {
case (id, name) => {
println(s"$id is $name")
}
}

Answer 2

With for you can extract the elements of the tuple,
for ( (s,o) <- list ) yield f(s,o)

Answer 3

I will suggest using map, filter,fold or foreach(whatever suits your need) rather than iterating over a collection using loop.
Edit 1:
e.g
if you want to apply some func foo(tuple) on each element
val newList=oldList.map(tuple=>foo(tuple))
val tupleStrings=tupleList.map(tuple=>tuple._1) //in your situation
if you want to filter according to some boolean condition
val newList=oldList.filter(tuple=>someCondition(tuple))
or simply if you want to print your List
oldList.foreach(tuple=>println(tuple)) //assuming tuple is printable
you can find example and similar functions here https://twitter.github.io/scala_school/collections.html

Answer 4

If you just want to get the strings you could map over your list of tuples like this:
// Just some example object
case class MyObj(i: Int = 0)
// Create a list of tuples like you have
val tuples = Seq(("a", new MyObj), ("b", new MyObj), ("c", new MyObj))
// Get the strings from the tuples
val strings = tuples.map(_._1)
// Output: Seq[String] = List(a, b, c)
Note: Tuple members are accessed using the underscore notation (which
is indexed from 1, not 0)