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ZIO

The mongo4cats-zio module defines type aliases and constructors which replace Cats Effect and FS2 with ZIO and ZIO-Streams, respectively. Similarly, mongo4cats-zio-embedded brings in embedded MongoDB runner implemented with ZIO effects. This provides more ergonomic way of integrating MongoDB with ZIO 2.

To get access to ZMongoClient, ZMongoDatabase and ZMongoCollection type aliases, the following dependency needs to be added:

libraryDependencies += "io.github.kirill5k" %% "mongo4cats-zio" % "<version>"

ZIO-compatible Embedded MongoDB can be brought in with:

libraryDependencies += "io.github.kirill5k" %% "mongo4cats-zio-embedded" % "<version>"

Next, all the essential classes will be available from:

import mongo4cats.zio._

Connecting to a database and accessing collections​

To establish a connection with a database, we need to create a ZMongoClient first. Once the client is built, this will give us access to its databases. Furthermore, with ZMongoDatabase we'll be able to browse document collections in the database.

import mongo4cats.zio._

val client = ZLayer.scoped[Any](ZMongoClient.fromConnectionString("mongodb://localhost:27017"))
val database = ZLayer.fromZIO(ZIO.serviceWithZIO[ZMongoClient](_.getDatabase("my-db")))
val collection = ZLayer.fromZIO(ZIO.serviceWithZIO[ZMongoDatabase](_.getCollection("docs")))

Embedded MongoDB​

ZIO-based embedded MongoDB is available from:

import mongo4cats.zio.embedded._

To use it in tests (or anywhere else), just extend EmbeddedMongo trait:

import mongo4cats.bson._
import mongo4cats.bson.syntax._
import mongo4cats.zio._
import mongo4cats.zio.embedded.EmbeddedMongo
import zio._
import zio.test._
import zio.test.Assertion._

object ZMongoCollectionSpec extends ZIOSpecDefault with EmbeddedMongo {
  override def spec = suite("A ZMongoCollection")(
    test("should store and retrieve documents") {
      withRunningEmbeddedMongo("localhost", 27017) {
        ZIO
          .serviceWithZIO[ZMongoDatabase] { db =>
            for {
              coll <- db.getCollection("coll")
              doc = Document("_id" := ObjectId.gen)
              insertResult <- coll.insertOne(doc)
              result <- coll.find.all
            } yield assert(result)(equalTo(List(doc)))
          }
          .provide(
            ZLayer.scoped(ZMongoClient.fromConnectionString(s"mongodb://localhost:27017")),
            ZLayer.fromZIO(ZIO.serviceWithZIO[ZMongoClient](_.getDatabase("my-db")))
          )
      }
    }
  )
}