biaoma-ty / scala-sbt-tutorial

Playground/sandbox to explore SBT capabilities and features

SBT Playground

I am using this repo to document some of my experiments to understand SBT better.

Some important key concepts are (obviously) ...

• Sub-Projects
• Settings, Tasks, ...
• Scopes
  • Project, Configuration, Task ...

I am (almost exclusively) use Build.scala, because it exposes the full power (and flexibility) of SBT. I am only using *.sbt to define the version (so that you have something to play around with to see how the *.sbt-files fit into it). In general I recommend to use Build.scala as much as possible, because sooner or later you will run into configuration issues, that will require you to use Build.scala and by then you want to know, how to use it.

Getting started

• Just run > sbt to compile ./project/Build.scala
• At the prompt run ...

  inspect show-time inspect hello-world show show-time show hell-world

• Edit Build.scala to play around with the settings
• Either restart sbt or run > reload to reload/recompile Build.scala

Getting into it

0.0.2

• Explore the difference between the configuration Compile and the task compile
• Explore if and how the build settings will override project settings
  • e.g. if there is a setting for ThisBuild in configuration Compile, then how will that become visible in sub-projects?
• Run > inspect hello-world and try to guess what the following commands will display

  show sub-project1/:hello-world show sub-project1/compile:hello-world show sub-project1/compile:compile::hello-world show sub-project2/compile:compile::hello-world show sub-project1/:compile::hello-world show sub-project2/*:compile::hello-world

0.0.3

• Create a dependency between show-timer and show-timer-upper
• And apply .toUpperCase to show-timer-upper

0.0.4

• Make sbt-assembly work
• This shows a lot of good stuff, e.g. ...
  • How to make one task depend on another (with <<=)
  • The difference between compile, package and publish
  • How to use Artifacts (for publishing something)
• To make it work you can run > sbt clean publish-local and can then run the jar files from the commandline (they are self-contained): > java -jar ./sub1/target/scala-2.9.2/sub-project1_2.9.2-0.0.1-assembly.jar and > java -jar ./sub2/target/scala-2.9.2/sub-project2_2.9.2-0.0.2-assembly.jar