如何调用 Scala 中的方法

Question

I have written some code in scala and created one method inside that now i want to call this method in another program but I'm not not getting any result after calling this method.

First Program

object helper_class {
  def driver {
    def main(args: Array[String]) {
      val sparksession = SparkSession.builder().appName("app").enableHiveSupport().getOrCreate();
      val filepath: String = args(0)
      val d1 = spark.sql(s"load data inpath '${args(0)}'  into table databasename.tablename")
      //some more reusable code
    }
  }
}

second Program

import  Packagename.helper_class.driver
object child_program {
  def main(args: Array[String]) {
    driver //I want to call this method from  helper_class
  }
}

if I'm removing def main(args: Array[String]) from 1st code its giving error near args(0) as args(0) not found args(0) I am planning to pass as spark-submit can someone please help me how should i Implement this.

Answer 1

The main method is your entry point to run a program. It can't be wrapped within another method. Thus, you can't wrap it within another method.

I think what you are trying to do, is to load some Spark setup code and then use that "driver" to do something else... This is my best guess on how that could work

object ChildProgram {
  def main(args: Array[String]): Unit = {
    val driver = Helper.driver(args)
    // do something with the driver
  }
}



object Helper {
    def driver(args: Array[String]) = {
      val sparksession = SparkSession.builder().appName("app").enableHiveSupport().getOrCreate()
      val filepath: String = args(0)
      val d1 = spark.sql(s"load data inpath '${args(0)}'  into table databasename.tablename")
      //some more reusable code

      // I am assuming you are going to return the driver here
    }
}

That said, I would highly recommend reading a bit on Scala before attempting to go down that route, because you are likely to face even more obstacles. If I am to recommend a resource, you can try the awesome book "Scala for the Impatient" which should get you up and running very quickly.