Scala - encapsulating data in objects

Question

Motivations

This question is about working with Lists of data in Scala, and about resorting to either tuples or class objects for holding data. Perhaps some of my assumptions are wrong, so there it goes.

My current approach

As I understand, tuples do not afford the possibility of elegantly addressing their elements beyond the provided ._1, ._2, etc. I can use them, but code will be a bit unpleasant wherever data is extracted far from the lines of code that had defined it.

Also, as I understand, a Scala Map can only use a single type declaration for its values, so it can't diversify the value type of its values except for the case of type inheritance. (to the later point, considering the use of a type hierarchy for Map values "diversity" - may seem to be very artificial unless a class hierarchy fits any "model" intuition to begin with).

So, when I need to have lists where each element contains two or more named data entities, e.g. as below one of type String and one of type List, each accessible through an intelligible name, I resort to:

case class Foo (name1: String, name2: List[String]) 
val foos: List[Foo] = ...

Then I can later access instances of the list using .name1 and .name2.

Shortcomings and problems I see here

When the list is very large, should I assume this is less performant or more memory consuming than using a tuple as the List's type? alternatively, is there a different elegant way of accomplishing struct semantics in Scala?

Wilfred Springer · Accepted Answer · 2014-09-28 15:50:40Z

2

In terms of performance, I don't think there is going to be any distinction between a tuple and an instance of a cases class. In fact, a tuple is an instance of a case class.

Secondly, if you're looking for another, more readable way to get the data out of the tuple, I suggest you consider pattern matching:

val (name1, name2) = ("first", List("second", "third"))

edited Sep 28, 2014 at 15:50

answered Sep 27, 2014 at 15:32

Wilfred Springer

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4 Comments

matanox Over a year ago

Yes, I know of this de-structuring syntax (excuse the Clojure jargon) but still appreciate it. The thing about this is that when you have a list of these, and you pass it all around and access it all over, the point is you do not want to remember the semantics of each field there, you want the compiler to know it for you... and the source code to tell it to the other guy/gal who will read it later on...

matanox Over a year ago

Thanks for digging the tuple class! I wonder where tuples of more than two elements are hiding there in scala core...

tuxdna Over a year ago

When the number of data members in your Tuple or Case class grows, you need to consider the 22 members limit that Scala has. It also impacts function parameters. Check this: issues.scala-lang.org/browse/SI-7296

Wilfred Springer Over a year ago

With Scala 2.11, that limit no longer applies for case classes.

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Scala - encapsulating data in objects

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