Guidance to a Scalaz newbie starting with Validation

[chrsan]

Hi!

I've been wanting to check out Scalaz for quite some time now but
never really had the chance to do so. Now I have a case where I need
some validation logic and thought that this must be a perfect
opportunity to scratch the surface of Scalaz. Sorry if this question
have been asked a 1000 times, but I need a jump start to get it going.

I've been using the query param logic in Unfiltered for validation and
will use this as an easy example to try to illustrate what I want to
do. Let's say I have a Map[String, String] and that I want to check
some keys and its values. I want to be able to do multiple validation
tests per value with errors accumulated. Like this:

case class Foobar(foo: Int, bar: Option[String])

val expected = for {
foo <- lookup("foo") is
required("is missing") is
nonempty("is empty") is
int(n => n + " is not an int") is
pred(n => n < 10, _ => "Number must be less than 10")
bar <- lookup("bar") is
is optional is trimmed
} yield Foobar(foo.get, bar.get)

expected(data) match {
case Right(foobar) => // Succesful validation
case Left(log) => // log = List of failures
}

In Unfiltered a validation tests short curcuit on first error. I.e.
for foo nonempty will not be done if required failed.

I would also be able to compose validations. Maybe I need to do the
check for foo in multiple contexts.

Thanks in advance,
Christer

[Diego Medina]

This is one of the best examples I have found so far showing validation
https://gist.github.com/970717

hope it helps

Diego

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Diego Medina
Lift/Scala Developer
di...@fmpwizard.com
http://www.fmpwizard.com

[Christer Sandberg]

Great! Thanks a lot. Will check it out right away.

/Christer