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February 17, 2016 15:44
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Util to do projection on case classes
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| object TestApp extends App { | |
| val temp = Temp("a", "b", List(1, 2, 3, 4)) | |
| val psetUtils: PsetUtils = new PsetUtils(classOf[Temp]) | |
| println("line 1: " + psetUtils.toMap(temp, List("a", "c"))) | |
| println("line 2: " + psetUtils.toMap(temp, List("a"))) | |
| println("line 3: " + psetUtils.toMap(temp, List("b"))) | |
| println("line 4: " + psetUtils.toMap(temp, List("c"))) | |
| println("line 5: " + psetUtils.toMap(temp, List("c", "a", "b"))) | |
| } | |
| /* | |
| OUTPUT: | |
| line 1: Map(a -> a, c -> List(1, 2, 3, 4)) | |
| line 2: Map(a -> a) | |
| line 3: Map(b -> b) | |
| line 4: Map(c -> List(1, 2, 3, 4)) | |
| line 5: Map(c -> List(1, 2, 3, 4), a -> a, b -> b) | |
| */ | |
| import scala.reflect.runtime.universe._ | |
| class PsetUtils(types: Class[_ <: Product]*) { | |
| private val mirror = runtimeMirror(getClass.getClassLoader) | |
| /** | |
| * extract the field name from the class type and store them in Map[String, Map[String, Int]] | |
| * the second Int is the index of the field in the Object. | |
| */ | |
| private val fieldsDeclaration = types.map(tg => tg.getSimpleName -> | |
| mirror.classSymbol(tg).toType.members | |
| .filter(_.isInstanceOf[MethodSymbol]) | |
| .filter(_.asInstanceOf[MethodSymbol].isCaseAccessor).map { | |
| case m: MethodSymbol => | |
| m.name.toString | |
| }.toList.reverse.zipWithIndex.toMap | |
| ).toMap | |
| /** | |
| * Convert the object to map with the fields you pass in. | |
| */ | |
| def toMap(obj: AnyRef, fields: List[String]): Map[String, Any] = { | |
| val className = obj.getClass.getSimpleName | |
| fieldsDeclaration.get(className) match { | |
| case None => Map.empty[String, Any] | |
| case Some(declaration) => { | |
| fields.map(name => { | |
| val fieldIndex = declaration(name) | |
| name -> obj.asInstanceOf[Product].productElement(fieldIndex) | |
| }).toMap | |
| } | |
| } | |
| } | |
| } | |
| case class Temp(a: String, b: String, c: List[Int]) | |
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can you add a bit of documentation internally to better explain your different steps?