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POUsing Either to process failures in Scala code
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  1. POUsing Either to process failures in Scala code
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    copied!<p><code>Option</code> monad is a great expressive way to deal with something-or-nothing things in Scala. But what if one needs to log a message when "nothing" occurs? According to the Scala API documentation,</p> <blockquote> <p>The Either type is often used as an alternative to scala.Option where Left represents failure (by convention) and Right is akin to Some.</p> </blockquote> <p>However, I had no luck to find best practices using Either or good real-world examples involving Either for processing failures. Finally I've come up with the following code for my own project:</p> <pre><code> def logs: Array[String] = { def props: Option[Map[String, Any]] = configAdmin.map{ ca =&gt; val config = ca.getConfiguration(PID, null) config.properties getOrElse immutable.Map.empty } def checkType(any: Any): Option[Array[String]] = any match { case a: Array[String] =&gt; Some(a) case _ =&gt; None } def lookup: Either[(Symbol, String), Array[String]] = for {val properties &lt;- props.toRight('warning -&gt; "ConfigurationAdmin service not bound").right val logsParam &lt;- properties.get("logs").toRight('debug -&gt; "'logs' not defined in the configuration").right val array &lt;- checkType(logsParam).toRight('warning -&gt; "unknown type of 'logs' confguration parameter").right} yield array lookup.fold(failure =&gt; { failure match { case ('warning, msg) =&gt; log(LogService.WARNING, msg) case ('debug, msg) =&gt; log(LogService.DEBUG, msg) case _ =&gt; }; new Array[String](0) }, success =&gt; success) } </code></pre> <p>(Please note this is a snippet from a real project, so it will not compile on its own)</p> <p>I'd be grateful to know how you are using <code>Either</code> in your code and/or better ideas on refactoring the above code.</p>
 

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