Mongo casbah: cannot resolve "++"

Question

Casbah version: 2.8.0

Following example here: http://api.mongodb.com/scala/casbah/2.0/tutorial.html#combining-multiple-dbobjects

I'm using below as import statements.

import com.mongodb.casbah.AggregationOutput
import com.mongodb.casbah.Imports._
import com.mongodb.casbah.TypeImports._
import com.mongodb.casbah.commons.{MongoDBList, MongoDBObject}

And below ++ got Cannot resolve symbol ++ error.

val basic = MongoDBObject(
  "id" -> "123",
  "project" -> "pp123"
)

val createdTime = MongoDBObject(
  "createdTime" -> MongoDBObject(
    "$exists" -> false
  )
)

val query = basic ++ createdTime

I tried to Google but didn't find much, the official documentation didn't help either...

I guess I'm just missing an import statement for ++, but I don't know which one to import.

score 1 · Accepted Answer · answered Jul 23 '16 at 01:57

A quick grep of the source reveals two ++ methods on the MongoDBObject class:

> grep -r "def ++" .
./casbah-commons/src/main/scala/MongoDBObject.scala:  def ++(pairs: (String, Any)*): DBObject = {
./casbah-commons/src/main/scala/MongoDBObject.scala:  def ++[A <% DBObject](other: A): DBObject = {

The second one looks relevant here. <% denotes a view bound, so you need an implicit conversion from MongoDBObject to DBObject.

> grep -r "implicit .*: DBObject =" .
./casbah-commons/src/main/scala/Implicits.scala:  implicit def map2MongoDBObject(map: scala.collection.Map[String, Any]): DBObject =
./casbah-commons/src/main/scala/Implicits.scala:  implicit def unwrapDBObj(in: MongoDBObject): DBObject = in.underlying

It looks like you can import com.mongodb.casbah.Implicits._ to get this.

Mongo casbah: cannot resolve "++"

1 Answers1