Automatic Dependency Injection in Scala - Just the Type System!
GitHub: https://github.com/scala/scala3/blob/...
Learn ZIO: https://rockthejvm.com/p/zio
In this video we will demonstrate a technique for automatic dependency injection in pure Scala with no other libraries or frameworks. Here, instances are passed automatically just by the structure of the types in question, without relying on macros, annotations, reflection or any runtime behavior. The technique is based on an example from Martin Odersky after an informal discussion (shared with his permission).
We'll cover
a scenario where dependency injection is useful
how explicit dependency injection is done
how the ZIO library manages dependency injection with ZLayers
how we can use givens, match types and a minimum of type-level programming to make the compiler automatically infer which instances need to be injected in which place
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