How to use flatMap for flatten one component of a tuple

Question

I have a tuple like.. (a, list(b,c,d)). I want the output like

(a,b)
(a,c)
(a,d)

I am trying to use flatMap for this but not getting any success. Even map is not helping in this case.

Input Data :

Chap01:Spark is an emerging technology
Chap01:You can easily learn Spark
Chap02:Hadoop is a Bigdata technology
Chap02:You can easily learn Spark and Hadoop

Code:

val rawData = sc.textFile("C:\\wc_input.txt")

val chapters = rawData.map(line => (line.split(":")(0), line.split(":")(1)))

val chapWords = chapters.flatMap(a => (a._1, a._2.split(" ")))

val chapWords = chapters.flatMap { case(a, b) => b.split(" ").map(word => a -> word) }. The problem is that flatMap expects a collection but you are passing it a tuple, so you need to map the collection to create a collection of tuples. — Luis Miguel Mejía Suárez
@LuisMiguelMejíaSuárez : Thanks for quick resolution. It worked. — Neeraj Kumar

senjin.hajrulahovic senjin.hajrulahovic · Accepted Answer · 2019-04-10T07:04:09

You could map over the second element of the tuple:

val t = ('a', List('b','c','d'))
val res = t._2.map((t._1, _))

The snipped above resolves to:

res: List[(Char, Char)] = List((a,b), (a,c), (a,d))

How to use flatMap for flatten one component of a tuple

2 Answers