Are you a Scala first-timer who find yourself fighting with the build system for even the simplest of tasks? Then this guide is for you. If you are a Scala veteran that just never bothers to remember the syntax, then this is for you as well.
Also, remember that this guide assumes SBT 0.13.x.
Let's go back to basic! This is how to prepare a project's base directory:
mkdir hello-world # your project dir
cd hello-world
touch build.sbt # sbt build definition file
mkdir -p src/main/scala # .scala files goes here
touch src/main/scala/Main.scala # your hello world program
Contents of build.sbt:
name := "hello-world" // you can change to any name
scalaVersion := "2.11.8" // and pick any scala version you want
Main.scala might look like:
object Main {
// let's do a bare minimum, working example
def main(args: Array[String]): Unit = println("hello world!")
}
If you are using Git, add the following directories to .gitignore. They are auto generated and you don't want them:
./project
./target
Now, try to run it from the base directory, hello-world. Remember, you must run it from the base directory.
sbt run
[info] Set current project to hello-world (in build file:/Users/lolski/Project/sbt-cheatsheet/01-initialization/)
[info] Updating {file:/Users/lolski/Project/sbt-cheatsheet/01-initialization/}root-01-initialization...
[info] Resolving jline#jline;2.12.1 ...
[info] Done updating.
[info] Compiling 1 Scala source to /Users/lolski/Project/sbt-cheatsheet/01-initialization/target/scala-2.11/classes...
[info] Running Main
hello world!
[success] Total time: 4 s, completed Jun 4, 2016 3:24:16 PM
Horray!
Specifying multiple dependencies one by one in build.sbt:
name := "hello-world"
scalaVersion := "2.11.8"
libraryDependencies += "org.apache.commons" % "commons-lang3" % "3.4"
libraryDependencies += "org.apache.commons" % "commons-io" % "1.3.2"
Alternatively, you can also specify them as a Seq
name := "hello-world"
scalaVersion := "2.11.8"
libraryDependencies ++= {
Seq(
"org.apache.commons" % "commons-lang3" % "3.4",
"org.apache.commons" % "commons-io" % "1.3.2"
)
}
SBT commands that are most likely to be used on a daily basis
sbt run # runs your program
sbt sbtVersion # displays sbt version
sbt console # opens REPL console
sbt compile # compiles project
sbt clean # clean
sbt "test-only org.yourcompany.YourTestSpec" # runs a single test
sbt test # runs every tests
sbt ";clean ;compile; run" # combines multiple commands in a single invocation