Krzysztof Jeliński jelinski

ZIO-like dependency injection using implicit resolution

Daniel Ciocîrlan recently published a video showcasing a dependency-injection (DI) approach developed by Martin Odersky that uses Scala's implicit resolution to wire dependencies automatically. (See also his reddit post.)

The basic pattern for defining services in Odersky's approach is as follows:

class Service(using Provider[(Dep1, Dep2, Dep3)])

This is a little trick to turn an executable Java jar.

It works on all unixy like systems including Linux, MacOS, Cygwin, and Windows Linux subsystem.

Step 1 Start with an all-in-one jar (with entry point and all deps within)

$ ls 
hello.jar

	scala> import shapeless._, syntax.singleton._, record._
	import shapeless._
	import syntax.singleton._
	import record._

	scala> object ->> {
	\| def unapply[K, V](f: FieldType[K, V])(implicit k: Witness.Aux[K]) = Option((k.value, f: V))
	\| }
	defined module $minus$greater$greater