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POAlternative to doing lots of calculations in constructor - scala
 

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    <p>I'm learning scala for a new project, aiming for immutability and functional style wherever possible. </p> <p>One of the objects I'm creating takes a number of inputs in its constructor, then repeatedly applies a large number of calculations to generate the relevant outputs, which are stored as fields on the object.</p> <p>While the calculations are performed and their results added to a mutable <code>ListBuffer</code> internally, everything else about the object is immutable - once created you can't change any of the input values and running the calculations again would obviously produce the same result.</p> <p>However, it doesn't seem right to me to have so many calculations in the constructor. The only way around it I can see is to have the calculated values be <code>var</code>s and provide a <code>run</code> method which performs the calculations - but then this method could be called multiple times, which would be pointless. </p> <p>Is it actually OK style to do a lot in a scala constructor? There's no calls to the DB for example, just internal calculations. Or is there some pattern for this?</p> <p>Here's the basic idea in very very simple form:</p> <pre><code>class Foo(val x:Int, val y:Int, calculations:List[Calculation]) { val xHistory = new collection.mutable.ListBuffer[Int]() val yHistory = new collection.mutable.ListBuffer[Int]() calculations.map { calc =&gt; calc.perform(this) }.foreach { result =&gt; xHistory += result.x yHistory += result.y } } </code></pre> <p>Basically I want the inputs wrapped in a handy instance of a <code>Foo</code> object so I can pass it to the various calculation strategies (each of which may need a different combination of inputs).</p>
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