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copied!<p>Have a look at <a href="http://www.scala-lang.org/api/rc/index.html#scala.util.Try" rel="nofollow">scala.util.Try</a>. It's available in Scala 2.10, which may or may not be available to you as an option, but the idea of it is perfect for your scenario.</p> <p>What you have in your code example is what I like calling the "pyramid" of nesting. The best solution to this is to use flat-mapping wherever you can. But obviously that's an issue when you have stuff like <code>Either[Exception, Result]</code> at every step. That's where <code>Try</code> comes in. <code>Try[T]</code> is essentially a replacement for <code>Either[Exception, T]</code>, and it comes with all of the <code>flatMap</code>-ing goodness that you need.</p> <p>Assuming you can either change the return type of those <code>webService</code> calls, or provide some implicit conversion from <code>Either[Exception, Result]</code> to <code>Try[Result]</code>, your code block would become something more like...</p> <pre><code>for { id <- dbService.insertIntoDb(someObject) r <- webService.callWebService1(id,someObject) context <- webService.callWebservice2(r,someObject) id2 <- dbService.insertContextIntoDb(context) response <- webService.callWebservice3(id,someObject).recoverWith { case e: Exception => webService.rollbackService3(); Failure(e) } } yield response </code></pre> <p>Lift has a similar mechanism in <a href="http://scala-tools.org/mvnsites/liftweb-2.4/#net.liftweb.common.Box" rel="nofollow">net.liftweb.common.Box</a>. It's like <code>Option</code>, but with a container for Exceptions too.</p> <p><strong>edit:</strong> It looks like you can use the <code>left</code> or <code>right</code> method of an <code>Either</code>, and it will let you use <code>flatMap</code>-ing almost exactly the way I described with <code>Try</code>. The only difference is that the end result is an <code>Either[Exception, Result]</code> instead of a <code>Try[Result]</code>. Check out <a href="http://www.scala-lang.org/api/current/index.html#scala.Either%24%24LeftProjection" rel="nofollow">LeftProjection</a> for details/examples.</p>

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