Flink Scala API "not enough arguments"

Question

I'm having troubles using Apache Flink Scala API

For example, even when I take the examples from the official documentation, the scala compiler gives me tons of compilation errors.

Code:

object TestFlink {

  def main(args: Array[String]) {
    val env = ExecutionEnvironment.getExecutionEnvironment
    val text = env.fromElements(
      "Who's there?",
      "I think I hear them. Stand, ho! Who's there?")

    val counts = text.flatMap { _.toLowerCase.split("\\W+") filter { _.nonEmpty } }
      .map { (_, 1) }
      .groupBy(0)
      .sum(1)

    counts.print()

    env.execute("Scala WordCount Example")
  }
}

Scala IDE outputs the following for the line val text = env.fromElements

Multiple markers at this line
  - not enough arguments for method fromElements: (implicit evidence$14: scala.reflect.ClassTag[String], implicit evidence$15: 
   org.apache.flink.api.common.typeinfo.TypeInformation[String])org.apache.flink.api.scala.DataSet[String]. Unspecified value parameter evidence$15.
  - could not find implicit value for evidence parameter of type org.apache.flink.api.common.typeinfo.TypeInformation[String]
  - could not find implicit value for evidence parameter of type org.apache.flink.api.common.typeinfo.TypeInformation[String]
  - not enough arguments for method fromElements: (implicit evidence$14: scala.reflect.ClassTag[String], implicit evidence$15: 
   org.apache.flink.api.common.typeinfo.TypeInformation[String])org.apache.flink.api.scala.DataSet[String]. Unspecified value parameter evidence$15.

It's not just fromElements method: even if I read from a file and then try to do something as simple as ds.map(r => r), I get something very similar

Multiple markers at this line
    - not enough arguments for method map: (implicit evidence$4: org.apache.flink.api.common.typeinfo.TypeInformation[K], implicit 
     evidence$5: scala.reflect.ClassTag[K])org.apache.flink.api.scala.DataSet[K]. Unspecified value parameters evidence$4, evidence$5.
    - could not find implicit value for evidence parameter of type org.apache.flink.api.common.typeinfo.TypeInformation[K]
    - could not find implicit value for evidence parameter of type org.apache.flink.api.common.typeinfo.TypeInformation[K]
    - not enough arguments for method map: (implicit evidence$4: org.apache.flink.api.common.typeinfo.TypeInformation[K], implicit 
     evidence$5: scala.reflect.ClassTag[K])org.apache.flink.api.scala.DataSet[K]. Unspecified value parameters evidence$4, evidence$5.

I tried two versions of Flink: 0.8.1 from Maven Central and the most fresh one from the github repository.

I'm running Windows 7, scala 2.10.4, jdk 1.7.0_25, Scala IDE version is 3.0.3-20140327-1716-Typesafe on top of Eclipse 4.3.0

What am I doing wrong?

Answer 1

You need to add the following import to your code:

import org.apache.flink.api.scala._ 

Then the example works.