Nested sequence iteration in scala, zip

Question

I have the following case classes

case class Outer(outerId: Integer, outerName: String, innerSeq:Seq[Inner]) case class Inner(innerName:String, innerAge: Integer, innerId: Integer)

I created the following instances

val innerSeq1 = Seq(Inner("in10",10, 0),Inner("in11",11, 1), Inner("in12",12, 2)) val innerSeq2 = Seq(Inner("in20",10, 0),Inner("in21",11, 1), Inner("in22",12, 2)) val outerSeq = Seq(Outer(1, "out1", innerSeq1), Outer(2, "out2", innerSeq2 ))

My intent is to create 3 element 3-tuples like this, I am not sure if I can use Zip or what to elegantly do this(I know a map then a map can do the iteration but I am not clear how will I get the below kind of output)

I want a 3-tuple in the following format (name of outer, name of inner, id of inner) Seq( (out1, in10, 0), (out1, in11, 1), (out1, in12, 2), (out2, in20, 0), (out2, in21, 1), (out2, in22, 2) ) Basically I want to while iterating over outersequence, want the triplets to be formed and get this flattened three tuplet output

So, you want one item for each outer, each one containing the triple of every inner, am I interpreting this correctly? — stefanobaghino
– stefanobaghino, Commented Jan 22, 2018 at 18:08
curiousengineer, I wonder if there is something wrong with my updated answer. If there is - could you point out what works not as you wanted? — SergGr
– SergGr, Commented Jan 22, 2018 at 18:43
@curiousengineer, I've also added a for-comprehension-based way in case you prefer that. — SergGr
– SergGr, Commented Jan 22, 2018 at 18:55

SergGr · Accepted Answer · 2018-01-22 18:54:48Z

2

Originally I misread your question. What you really want can be achieve with flatMap and inner map like this:

outerSeq.flatMap(o => o.innerSeq.map(i => (o.outerName, i.innerName, i.innerId)))

If you prefer for-comprehension it might be even easier:

val res = for (o <- outerSeq; i <- o.innerSeq) yield (o.outerName, i.innerName, i.innerId)

edited Jan 22, 2018 at 18:54

answered Jan 22, 2018 at 18:06

SergGr

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2 Comments

curiousengineer Over a year ago

thanks. Which is more functional :)? I remember, internally, one gets compiled into another though!

SergGr Over a year ago

@curiousengineer, yes as the linked article says for-comprehension is compiled to exactly the same code. As to which is more functional, I think it is a question of taste. I think for-comprehension in this specific case produces a simpler code with a more clear intent. However others are entitled to different opinion.

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