Scala beginner on compiling and running scala programs on multiple files

Question

I am working through the examples in ScalaInAction and I am having trouble running examples which spread across multiple files and a placed in a single package.

Here is the code.

mongoclient.scala

package com.scalainaction.mongo
import com.mongodb._

class MongoClient(val host:String, val port:Int) {
    require(host != null, "You have to provide a host name")
    val underlying = new com.scalainaction.mongo.Mongo
    def this() = this("127.0.0.1", 27017)
    def version = underlying.getVersion
    def dropDB(name:String) = underlying.dropDatabase(name) 
    def createDB(name:String) = DB(underlying.getDB(name)) 
    def db(name:String) = DB(underlying.getDB(name))
}

DB.scala

package com.scalainaction.mongo
import com.mongodb.{DB => MongoDB}
import scala.collection.convert.Wrappers._

class DB private(val underlying: MongoDB) {
    private def collection(name: String) = underlying.getCollection(name)
    def readOnlyCollection(name: String) = new DBCollection(collection(name)) 

    def administrableCollection(name: String) = new
        DBCollection(collection(name)) with Administrable

    def updatableCollection(name: String) = new
        DBCollection(collection(name)) with Updatable

    def collectionNames = for(name 

DBCollection.scala

package com.scalainaction.mongo
import com.mongodb.{DBCollection => MongoDBCollection } 
import com.mongodb.DBObject

class DBCollection(override val underlying: MongoDBCollection) extends ReadOnly

trait ReadOnly {
  val underlying: MongoDBCollection
  def name = underlying.getName
  def fullName = underlying.getFullName
  def find(doc: DBObject) = underlying.find(doc)
  def findOne(doc: DBObject) = underlying.findOne(doc)
  def findOne = underlying.findOne
  def getCount(doc: DBObject) = underlying.getCount(doc)
}

trait Administrable extends ReadOnly {
  def drop: Unit = underlying.drop
  def dropIndexes: Unit = underlying.dropIndexes
}

trait Updatable extends ReadOnly {
  def -=(doc: DBObject): Unit = underlying.remove(doc)
  def +=(doc: DBObject): Unit = underlying.save(doc)
}

All the programs are placed inside the same package com.scalainaction.mongo.

I don't use an IDE so I compile these files by running

scalac mongoclient.scala DB.scala DBCollection.scala

My $CLASSPATH includes the mongodb.jar file and also points to com.scalainaction.mongo folder in my application directory

And now I intend to run a program which uses the package by running scala quickTour.scala -cp $CLASSPATH`

import com.scalainaction.mongo._
import com.mongodb.BasicDBObject

def client = new MongoClient("127.0.0.1", 27017)
def db = client.db("mydb")

for(name 

But my application is unable to find the MongoClient class and I get this error

quickTour.scala:1: error: object scalainaction is not a member of package com
import com.scalainaction.mongo._
           ^
/Users/sid/scala_apps/quickTour.scala:4: error: MongoClient does not have a constructor
def client = new MongoClient("127.0.0.1", 27017)
             ^
two errors found

I don't follow why it doesn't find the constructor. I have defined an overloaded constructor with the def this method

Why can't it find com.scalanation.mongo?

I would appreciate any help on this

** UPDATE **

Files in my com/scalainaction/mongo folder are

Administrable$class.class       DB$.class               ReadOnly$class.class
Administrable.class         DB.class                ReadOnly.class
DB$$anon$1.class            DBCollection.class          Updatable$class.class
DB$$anon$2.class            MongoClient$$anonfun$1.class        Updatable.class
DB$$anonfun$collectionNames$1.class MongoClient.class

Answer 1

The problem is that your folder com and/or com/scalainaction is empty. Put some classes there and it should work.