Dependencies

Add a Managed Library Dependency

libraryDependency is the SettingKey that handles ‘managed’ library dependencies, which are dependencies that are automatically downloaded, matching the supplied versions. To add a single dependency:

libraryDependencies += "com.typesafe.slick" %% "slick" % "3.2.0-M1"

The first part, "com.typesafe.slick", indicates the library package. The second part, "slick", is the library in question. The final part, "3.2.0-M1", is the version. Because the library is joined by %% the version of Scala supplied by the scalaVersion setting key will be utilized.

You can add multiple libraries at once using ++=:

libraryDependencies ++= Seq(
  "com.typesafe.slick" %% "slick" % "3.2.0-M1" % "compile",
  "com.typesafe.slick" %% "slick-hikaricp" % "3.2.0-M1",
  "mysql" % "mysql-connector-java" % "latest.release"
)

Remember Scala’s functional nature, allowing you to compute dependencies. Just remember to return a Seq:

libraryDependencies ++= {
  lazy val liftVersion = "3.0-RC3" //Version of a library being used
  lazy val liftEdition = liftVersion.substring(0,3) //Compute a value
  Seq(
    "net.liftweb" %% "lift-webkit" % liftVersion % "compile",  // Use var in Seq
    "net.liftmodules" %% ("ng_" + liftEdition) % "0.9.2" % "compile",  // Use computed var in Seq
  )  // Because this is the last statement, the Seq is returned and appended to libraryDependencies
}

Add a Repository

A repository is a place that SBT looks for libraryDependencies. If the build complains about not finding a dependency, it can be lacking the correct repository. Within SBT, the repositories are listed in the resolvers SettingKey:

resolvers += "Flyway" at "https://flywaydb.org/repo"

This follows the syntax of ‘Repository name’ at ‘url location’.

Pin Library to Project Version of Scala

If your project has this:

scalaVersion := 2.11  // Replace '2.11' with the version of Scala your project is running on

Then you can use %% to automatically get the version of the library compiled against the version of Scala the project is using:

libraryDependencies += "com.typesafe.slick" %% "slick" % "3.2.0-M1"

Note that having the above two lines is equivalent to having this one line:

libraryDependencies += "com.typesafe.slick" % "slick_2.11" % "3.2.0-M1"

Pin Library to Specific Version of Scala

A library can be ‘pinned’ to a specific version of Scala using the % operator between the groupId and the artifactId (the first two strings in a library dependency). In this example, we pin the library with the artifactId of slick to Scala version 2.10:

 libraryDependencies += "com.typesafe.slick" % "slick_2.10" % "3.2.0-M1"