How can I access a method which return Option object?

问题

I have to call method which returns Option[List[Obj]].

After I call I need to iterate the List and print the Obj attributes.

object Tester{
  def main(args:Array[String]) {
    val ymlFilename ="some.yml";
  val entities: Option[QueryEntities] =  InputYamlProcessor.process(ymlFilename)

        for( e: QueryEntities  <- entities ){
          /// this is not working
           //How to access the columnFamily, fromData and toDate ?
        }
  }

Complete sample

https://gist.github.com/shatestest/fdeaba767d78e171bb6c08b359fbd1bf

回答1:

The most iconic way ot do it is to unwrap values with scala is to use pattern matching to unwrap the value.

entities match {
    case Some(queryEntities: QueryEntities) => 
      queryEntities.entities.foreach { case e =>
        println(e.columnFamily)
        println(e.fromDate.getOrElse("defaultFromDateHere")
        println(e.toDate.getOrElse("defaultToDateHere"))
      }
    case None => println("No value")
}

来源：https://stackoverflow.com/questions/53152042/how-can-i-access-a-method-which-return-option-object