如何将案例类作为变量传递到ScalaReflection [英] How to pass case class as a variable into ScalaReflection

问题描述

我试图将案例类作为变量传递给ScalaReflection以获取架构.

I am trying to pass a case class as a variable to ScalaReflection to get the schema.

我能够使用案例类名称成功运行代码，就像将案例类分配给变量并将其传递给ScalaReflection一样，我遇到了错误.

I am able to run the code successfully with case class name where as when I assign the case class to a variable and pass that to ScalaReflection I am getting error.

这是我的代码

import org.apache.spark.sql.catalyst.ScalaReflection
import org.apache.spark.sql.types.StructType

case class Emp (empId: Integer, empName: String)
val myschema = ScalaReflection.schemaFor[Emp].dataType.asInstanceOf[StructType]
println(myschema)

val empModel = Emp
val myschema2 = ScalaReflection.schemaFor[empModel].dataType.asInstanceOf[StructType]

Error: error: not found: type empModel
val myschema2 = ScalaReflection.schemaFor[empModel].dataType.asInstanceOf[StructType]

任何建议都是有帮助的！

Any suggestion is helpful!

推荐答案

类型同义词(=别名)应使用关键字 type

Type synonyms (= aliases) should be introduced with a keyword type

type empModel = Emp
val myschema2 = ScalaReflection.schemaFor[empModel].dataType.asInstanceOf[StructType]

在Scala中，值和类型构成不同的名称空间.

In Scala values and types make different namespaces.

具有 type (和 val )的顶级定义，因此它们必须位于某个对象之内

Top definitions with type (and val) are not allowed in Scala 2, so they have to be inside some object

object App {
  type empModel = Emp
  val myschema2 = ScalaReflection.schemaFor[empModel].dataType.asInstanceOf[StructType]
}

这篇关于如何将案例类作为变量传递到ScalaReflection的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！