Create complex data from Strings in Scala

Question

I have defined a number of case classes such as

  abstract class Foo
  case class Bar(s: String) extends Foo
  case class Baz(f: Foo) extends Foo
  case class FooBar(l: Foo, r:Foo)

that allow me to create complex data, e.g.,

  val x = FooBar(Bar("1"), Baz(Bar("2")))

I want to read these type of data from a string, such as

  val x = what_to_do_here?("FooBar(Bar("1"), Baz(Bar("2")))")

~~In a dynamic language I would just call eval.~~ (Edit: I really do not want to call something like eval in scala)

The solution I came up with in scala was to write a parser. Is there a simpler way to do that?

Related: stackoverflow.com/questions/1183645/eval-in-scala

Arjan Blokzijl
– Arjan Blokzijl

2011-09-27 05:10:06 +00:00
Commented Sep 27, 2011 at 5:10 — Arjan Blokzijl
– Arjan Blokzijl, Commented Sep 27, 2011 at 5:10

Tomer Gabel · Accepted Answer · 2011-09-27 10:24:11Z

2

You are assuming that there's a construct that's symmetric with toString. I'm pretty sure there isn't one.

Since what you're discussing is a classic serialization/deserialization scenario, you may want to look into a serialization library (one possibility that comes to mind is lift-json, which with I've had considerable success, but there are certainly alternatives). Either that, or I've completely missed your usage scenario :-)

answered Sep 27, 2011 at 10:24

Tomer Gabel

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2 Comments

Joe Lehmann Over a year ago

It is indeed a deserialization szenario. However, I cannot control the output of the serialization (because I do not own the code) so using a library isn't an option. I think I'll have to write a little parser

Tomer Gabel Over a year ago

You could, as you suggest, mock it by integrating the Scala REPL, but I wouldn't recommend it. A simple parser would be much simpler to implement and less error-prone (assuming a reasonable set of classes).

Kim Stebel · Accepted Answer · 2011-09-27 04:43:01Z

1

You can use the scala interpreter to write your own eval function. Since the interpreter is actually a compiler, I don't think this will be very fast.

answered Sep 27, 2011 at 4:43

Kim Stebel

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