How to implement generic function that receives differents types scala

    import org.apache.spark.{ SparkConf, SparkContext }
    import org.apache.spark.rdd.RDD

    class BaseType(val a: String) extends Serializable {
     override def toString = "(" + a + ")"
    }
    class TypeA(a: String, val b: String) extends BaseType(a) {
     override def toString = "(" + a + "," + b + ")"
    }
    class TypeB(a: String, val b: String) extends BaseType(a) {
     override def toString = "(" + a + "," + b + ")"
    }

   object EntityInheritance {
    def main(args: Array[String]) = {

    val sparkConf = new SparkConf()
      .setMaster("local[*]")
      .setAppName("EntityInheritance Sample")

    val sc = new SparkContext(sparkConf)

    val text_file = sc.textFile("/dqa/sample_logs/tipologies/entityInheritance.txt")
    val items = text_file.flatMap(_.split("\n"))

        val itemsRDDa = items.map(newInstanceA(_))
        itemsRDDa.foreach { rdd => println(rdd) }
        val countAa = countersAttributeA[TypeA](itemsRDDa)

        val itemsRDDb = items.map(newInstanceB(_))
    itemsRDDb.foreach { rdd => println(rdd) }
        val countBa = countersAttributeA[TypeB](itemsRDDb)

    sc.stop()
  }

    def newInstanceA(str: String): TypeA = {
      val parts = str.split(" ")
      new TypeA(parts(0), parts(1))
    }

    def newInstanceB(str: String): TypeB = {
        val parts = str.split(" ")
        new TypeB(parts(0), parts(1))
    }

    // I want to implement a generic function that receives RDD[TypeA] or RDD[TypeB]
    // it's a simple example
     def countersAttributeA[A](rdd: org.apache.spark.rdd.RDD[A]) = {
       rdd
        .map(s => (s.a, 1))
        .reduceByKey(_ + _)
     }
   }

Hello, I have a problem but is possible that this idea is isn't good.

I trying to implement a generic function that receives different types. When create a different objects for example TypeA and TypeB I want to send to counterAttributeA -> count number of apparences of attribute 'a', but the console send this error:

[error] /src/main/scala/org/sparklambda/testing/EntityInheritance.scala:53: value a is not a member of type parameter A
[error]       .map(s => (s.a, 1))
[error]                    ^
[error] one error found

Anyone you can help me? Thank's for all.

Copyright Notice：Content Author:「Diego Sanz」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/44436433/how-to-implement-generic-function-that-receives-differents-types-scala