Scala Cookbook

18.6. Creating a Project with Subprojects

Problem

You want to configure SBT to work with a main project that depends on other subprojects you’re developing.

Solution

Create your subproject as a regular SBT project, but without a project subdirectory. Then, in your main project, define a project/Build.scala file that defines the dependencies between the main project and subprojects.

This is demonstrated in the following example, which I created based on the SBT Multi-Project documentation:

import sbt._
import Keys._

/**
 * based on http://www.scala-sbt.org/release/docs/Getting-Started/Multi-Project
 */
object HelloBuild extends Build {

  // aggregate: running a task on the aggregate project will also run it
  // on the aggregated projects.
  // dependsOn: a project depends on code in another project.
  // without dependsOn, you'll get a compiler error: "object bar is not a
  // member of package com.alvinalexander".
  lazy val root = Project(id = "hello",
                        base = file(".")) aggregate(foo, bar) dependsOn(foo, bar)

  // sub-project in the Foo subdirectory
  lazy val foo = Project(id = "hello-foo",
                         base = file("Foo"))

  // sub-project in the Bar subdirectory
  lazy val bar = Project(id = "hello-bar",
                         base = file("Bar"))
}

To create your own example, you can either follow the instructions in the SBT Multi-Project documentation to create a main project with subprojects, or clone my SBT Subproject Example on GitHub, which I created to help you get started quickly.

Discussion

Creating a main project with subprojects ...