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POcase class copy 'method' with superclass
 

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    <p>I want to do something like this:</p> <pre class="lang-scala prettyprint-override"><code>sealed abstract class Base(val myparam:String) case class Foo(override val myparam:String) extends Base(myparam) case class Bar(override val myparam:String) extends Base(myparam) def getIt( a:Base ) = a.copy(myparam="changed") </code></pre> <p>I can't, because in the context of getIt, I haven't told the compiler that every Base has a 'copy' method, but copy isn't really a method either so I don't think there's a trait or abstract method I can put in Base to make this work properly. Or, is there?</p> <p>If I try to define Base as <code>abstract class Base{ def copy(myparam:String):Base }</code>, then <code>case class Foo(myparam:String) extends Base</code> results in <code>class Foo needs to be abstract, since method copy in class Base of type (myparam: String)Base is not defined</code></p> <p>Is there some other way to tell the compiler that all <code>Base</code> classes will be case classes in their implementation? Some trait that means "has the properties of a case class"?</p> <p>I could make Base be a case class, but then I get compiler warnings saying that inheritance from case classes is deprecated?</p> <p>I know I can also:</p> <pre class="lang-scala prettyprint-override"><code>def getIt(f:Base)={ (f.getClass.getConstructors.head).newInstance("yeah").asInstanceOf[Base] } </code></pre> <p>but... that seems very ugly.</p> <p>Thoughts? Is my whole approach just "wrong" ?</p> <p><strong>UPDATE</strong> I changed the base class to contain the attribute, and made the case classes use the "override" keyword. This better reflects the actual problem and makes the problem more realistic in consideration of Edmondo1984's response.</p>
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    1. COcan you please explain what do you want to obtain by overriding a val in a case class?
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    2. COwell, it won't have a value in the abstract super class. Maybe seeing the actual program would help this question make more sense, in the actual code the "Base" class is the abstract sealed "Piece" class defined in this file: https://github.com/nairbv/scalachess/blob/master/src/main/scala/BoardState.scala ... as a temporary hack, I threw in the ugly cast I mentioned as a possibility in the original question.
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