How to import several implicit at once?

Question

I have several implicit context for my application. like

 import scala.collection.JavaConversions._    
  import HadoopConversion._   
etc

Right now I have to copy paste all those imports at each file. Is it possible to combine them in one file and make only one import?

Answer 1

A good technique that some libraries provide by default is bundling up implicits into a trait. This way you can compose sets of implicits by defining a trait that extends other implicit bundling traits. And then you can use it at the top of your scala file with the following.

import MyBundleOfImplicits._

Or be more selective by mixing it in only where you need it.

object Main extends App with MyBundleOfImplicits {
   // ...
}

Unfortunately with something like JavaConversions, to use this method you will need to redefine all the implicits you want to use inside a trait.

trait JavaConversionsImplicits {
  import java.{lang => jl}
  import java.{util => ju}
  import scala.collection.JavaConversions  
  implicit def asJavaIterable[A](i : Iterable[A]): jl.Iterable[A] = JavaConversions.asJavaIterable(i)
  implicit def asJavaIterator[A](i : Iterator[A]): ju.Iterator[A] = JavaConversions.asJavaIterator(i)
}

trait MyBundleOfImplicits extends JavaConversionsImplicits with OtherImplicits

Answer 2

Scala does not have first-class imports. So the answer to your question is no. But there is an exception for the scala REPL. You can put all your imports in a file and then just tell the REPL where it is located. See this question.