如何访问返回Option对象的方法

Question

我必须调用返回Option[List[Obj]]的方法。

调用后，我需要迭代List并打印Obj属性。

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 ?
}
}

完整样品

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

Answer 1

使用scala打开值的最具标志性的方法是使用模式匹配来打开值。

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")
}