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PODifference between object with main() and extends App in scala
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  1. PODifference between object with main() and extends App in scala
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    copied!<p>I'm working through ScalaInAction (book is still a MEAP, but code is public on github) Right now I'm in chapter 2 looking at this restClient: : <a href="https://github.com/nraychaudhuri/scalainaction/blob/master/chap02/RestClient.scala" rel="nofollow">https://github.com/nraychaudhuri/scalainaction/blob/master/chap02/RestClient.scala</a></p> <p>First, I setup intelliJ with scala extensions and created a HelloWorld with <code>main()</code>:</p> <pre><code>&lt;ALL the imports&gt; object HelloWorld { def main(args: Array[String]) { &lt;ALL the rest code from RestClient.scala&gt; } } </code></pre> <p>I get the following error when compiling:</p> <pre><code>scala: forward reference extends over defintion of value command val httppost = new HttpPost(url) ^ </code></pre> <p>I can fix this by moving the following lines around until the ordering is correct with relation to the <code>def</code>'s</p> <pre><code>require( args.size &gt;= 2, "You need at least two arguments to make a get, post, or delete request") val command = args.head val params = parseArgs(args) val url = args.last command match { case "post" =&gt; handlePostRequest case "get" =&gt; handleGetRequest case "delete" =&gt; handleDeleteRequest case "options" =&gt; handleOptionsRequest } </code></pre> <p>While browsing the github page, I found this: <a href="https://github.com/nraychaudhuri/scalainaction/tree/master/chap02/restclient" rel="nofollow">https://github.com/nraychaudhuri/scalainaction/tree/master/chap02/restclient</a></p> <p>Which uses implements RestClient.scala using <code>extends App</code> instead of a <code>main()</code> method:</p> <pre><code>&lt;All the imports&gt; object RestClient extends App { &lt;All the rest of the code from RestClient.scala&gt; } </code></pre> <p>I then changed my <code>object HelloWorld</code> to just use <code>extends App</code> instead of implementing a <code>main()</code> method and it works without errors</p> <p>Why does the <code>main()</code> method way of doing this generate the error but the <code>extends App</code> does not? </p>
 

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