Getting Started summary
This page wraps up the Getting Started Guide.
To use sbt, there are a small number of concepts you must understand.
These have some learning curve, but on the positive side, there isn’t
much to sbt except these concepts. sbt uses a small core of powerful
concepts to do everything it does.
If you’ve read the whole Getting Started series, now you know what you
need to know.
sbt: The Core Concepts
- the basics of Scala. It’s undeniably helpful to be familiar with
Scala syntax. Programming in
Scala written
by the creator of Scala is a great introduction.
- .sbt build definition
- your build definition is one big list of
Setting objects, where a
Setting transforms the set of key-value pairs sbt uses to perform
tasks.
- to create a
Setting, call one of a few methods on a key: :=, +=, or
++=.
- there is no mutable state, only transformation; for example, a
Setting transforms sbt’s collection of key-value pairs into a new
collection. It doesn’t change anything in-place.
- each setting has a value of a particular type, determined by the
key.
- tasks are special settings where the computation to produce the
key’s value will be re-run each time you kick off a task. Non-tasks
compute the value once, when first loading the build definition.
- Scopes
- each key may have multiple values, in distinct scopes.
- scoping may use three axes: configuration, project, and task.
- scoping allows you to have different behaviors per-project,
per-task, or per-configuration.
- a configuration is a kind of build, such as the main one (
Compile)
or the test one (Test).
- the per-project axis also supports “entire build” scope.
- scopes fall back to or delegate to more general scopes.
- .sbt vs. .scala build definition
- put most of your configuration in
build.sbt, but use .scala build
definition files for defining classes and larger task
implementations.
- the build definition is an sbt project in its own right, rooted in
the project directory.
- Plugins are extensions to the build definition
- add plugins with the
addSbtPlugin method in project/plugins.sbt (NOT
build.sbt in the project’s base directory).
If any of this leaves you wondering rather than nodding, please
ask for help, go back and re-read, or try some
experiments in sbt’s interactive mode.
Good luck!
Advanced Notes
Since sbt is open source, don’t forget you can check out the
source code too!
