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POScala: Self types in Constructors for generic classes
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  1. POScala: Self types in Constructors for generic classes
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    copied!<p>Here's a taste of the C# code that I'm porting into Scala. No need to worry about the details.</p> <pre><code>public class GridBase&lt;HexT, SideT, UnitT, SegT&gt; : IGridBase where HexT : Hex where SideT : Side where UnitT : Unit where SegT : ISeg { public GridBase(Geometry&lt;HexT, SideT, UnitT, SegT&gt; geom, IGridBase orig) { this.geom = geom; } } public class Scen: Descrip&lt;HexC, SideC, UnitC&gt;, IListsGeom&lt;HexC, SideC, UnitC&gt; { public Geometry&lt;HexC, SideC, UnitC, ISegC&gt; geomC; public override IGeom iGeom { get { return geomC; } } public HexCList hexCs { get; private set; } public override HexList&lt;HexC&gt; hexs { get { return hexCs; } } public SideCList sideCs { get; private set; } public override SideList&lt;SideC&gt; sides { get { return sideCs; } } public UnitCList unitCs { get; private set; } public override KeyList&lt;UnitC&gt; units { get { return unitCs; } } } </code></pre> <p>As Martin Odersky has pointed out the problem with generics is that the number of type parameters references and their restraint references tend to explode. However for the GridBase class, I need to resolve the types via generics rather than by abstract types. So I want to be able to get multiple types out of one type parameter. So in Scala I create a trait for my types:</p> <pre><code>abstract class Hex(val num1: Int){} //These are declared in their own files abstract class Side {val sideString = "This is a side"} trait DescripTypes //separate file { type HexT &lt;: Hex type SideT &lt;: Side } class ScenTypes extends DescripTypes //separate file { //This is an ex of an implemntation of the above in a different package type HexT = HexC type SideT = SideC } </code></pre> <p>Then I create my Gridbase class using a self type</p> <pre><code>class GridBase[T &lt;: DescripTypes](val myHex: HexT) extends DescripTypes {//Compiler doesn't recognise the HexT type in the constructor other: DescripTypes =&gt; type other = T var testvar = 5 //The rest does nothing at useful at the moment var testvar2 = "" //just for testing def mymethod(var1: HexT) //Compiler recognises HexT { testvar += var1.num1 //This compiles fine } def method2(var1: SideT) //Compiler recognises SideT { testvar2 = var1.sideString //This compiles fine } </code></pre> <p>}</p> <p>For some reason I can't seem to use the type members of DescripTypes in the GridBase Class constructor, although I can use them fine inside the class body. Any help appreciated. But also is this the best way to get multiple types out of one type parameter?</p> <p>Clarification: All Classes are in separate files. No inner classes here.</p>
 

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