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POConfiguration data in Scala -- should I use the Reader monad?
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copied!<p>How do I create a properly functional configurable object in Scala? I have watched Tony Morris' video on the <code>Reader</code> monad and I'm still unable to connect the dots. </p> <p>I have a hard-coded list of <code>Client</code> objects: </p> <pre><code>class Client(name : String, age : Int){ /* etc */} object Client{ //Horrible! val clients = List(Client("Bob", 20), Client("Cindy", 30)) } </code></pre> <p>I want <code>Client.clients</code> to be determined at runtime, with the flexibility of either reading it from a properties file or from a database. In the Java world I'd define an interface, implement the two types of source, and use DI to assign a class variable:</p> <pre><code>trait ConfigSource { def clients : List[Client] } object ConfigFileSource extends ConfigSource { override def clients = buildClientsFromProperties(Properties("clients.properties")) //...etc, read properties files } object DatabaseSource extends ConfigSource { /* etc */ } object Client { @Resource("configuration_source") private var config : ConfigSource = _ //Inject it at runtime val clients = config.clients } </code></pre> <p>This seems like a pretty clean solution to me (not a lot of code, clear intent), but that <code>var</code> <em>does</em> jump out (OTOH, it doesn't seem to me <em>really</em> troublesome, since I know it <em>will</em> be injected once-and-only-once). </p> <p>What would the <code>Reader</code> monad look like in this situation and, explain it to me like I'm 5, what are its advantages? </p>

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