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    <p><a href="http://www.scala-lang.org/node/112" rel="nofollow noreferrer">Extractors</a> which allow you to replace messy <code>if-elseif-else</code> style code with patterns. I know that these are not exactly <em>hidden</em> but I've been using Scala for a few months without really understanding the power of them. For (a long) example I can replace:</p> <pre><code>val code: String = ... val ps: ProductService = ... var p: Product = null if (code.endsWith("=")) { p = ps.findCash(code.substring(0, 3)) //e.g. USD=, GBP= etc } else if (code.endsWith(".FWD")) { //e.g. GBP20090625.FWD p = ps.findForward(code.substring(0,3), code.substring(3, 9)) } else { p = ps.lookupProductByRic(code) } </code></pre> <p>With this, which is <strong>much</strong> clearer in my opinion</p> <pre><code>implicit val ps: ProductService = ... val p = code match { case SyntheticCodes.Cash(c) =&gt; c case SyntheticCodes.Forward(f) =&gt; f case _ =&gt; ps.lookupProductByRic(code) } </code></pre> <p>I have to do a bit of legwork in the background...</p> <pre><code>object SyntheticCodes { // Synthetic Code for a CashProduct object Cash extends (CashProduct =&gt; String) { def apply(p: CashProduct) = p.currency.name + "=" //EXTRACTOR def unapply(s: String)(implicit ps: ProductService): Option[CashProduct] = { if (s.endsWith("=") Some(ps.findCash(s.substring(0,3))) else None } } //Synthetic Code for a ForwardProduct object Forward extends (ForwardProduct =&gt; String) { def apply(p: ForwardProduct) = p.currency.name + p.date.toString + ".FWD" //EXTRACTOR def unapply(s: String)(implicit ps: ProductService): Option[ForwardProduct] = { if (s.endsWith(".FWD") Some(ps.findForward(s.substring(0,3), s.substring(3, 9)) else None } } </code></pre> <p>But the legwork is worth it for the fact that it separates a piece of business logic into a sensible place. I can implement my <code>Product.getCode</code> methods as follows..</p> <pre><code>class CashProduct { def getCode = SyntheticCodes.Cash(this) } class ForwardProduct { def getCode = SyntheticCodes.Forward(this) } </code></pre>
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    1. COisn't this like a switch? maybe this could be refactored more.
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    2. COPatterns are like turbo-charged switches: much more powerful and clear
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    3. CONice, but I don't like that you have to use implicit because its scope reaches further than the match { }. You could also just add a method to ProductService that looks up a Product by code. You would wrap your refactored snippet in a method anyway to be able to use it everywhere.
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