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Scalaz TryOps

In this post we’ll look at TryOps and the goodies it provides to work with scala.util.Try. To recap, here’s what Try does:

The Try type represents a computation that may either result in an exception, or return a successfully computed value. It’s similar to, but semantically different from the scala.util.Either type.

Converting to a Disjunction

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@ import scalaz._
import scalaz._
@ import Scalaz._
import Scalaz._
@ import scala.util.Try
import scala.util.Try
// an operation that may potentially throw an exception
@ val t1 = Try { "1".toInt }
t1: Try[Int] = Success(1)
// converting to a Scalaz disjunction
@ val disjunction = t1 toDisjunction
disjunction: Throwable \/ Int = \/-(1)

The result of a Try is either a Success or a Failure. This can very easily be translated to a Scalaz disjunction. A Success produces a right disjunction whereas a Failure produces a left disjunction.

Converting to a Validation

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@ val validation = t1 toValidation
validation: Validation[Throwable, Int] = Success(1)

Similarly, if this Try were a part of validating your data like checking values in a JSON object, you can convert this to a Scalaz Validation.

Converting to a ValidationNel

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@ val nel = t1 toValidationNel
nel: ValidationNel[Throwable, Int] = Success(1)

ValidationNel is useful for accumulating errors. We’ll cover all of this in coming posts.

Conclusion

This brings us to the end of the post on TryOps. In coming posts we’ll look at Validation type which lets us represent, as you might have guessed, the result of validating an input. Similarly, if we want to accumulate all the results of validating inputs, we use ValidationNel. Both of these are subjects of coming posts.