4 ms·

I'd like to see a language with baked in support for dependency injections, so that my functions can take two types of parameters: its "real" parameters, which

I'd like to see a language with baked in support for dependency injections, so that my functions can take two types of parameters: its "real" parameters, which it needs to perform its function, and "dependencies", that are passed implicitly by the runtime. Basically, a formalization of Dagger/Guice into a language.

keybored 4y ago
People have written drafts of a design for this for Rust. Calling it capabilities.
- dymk 4y ago
  As a part of the language standard / standard library, or as a third party crate? I'm confused how this would work, as as far as I'm aware, making this a language-level feature would require significant changes to the ethos of the language. There are some examples, e.g. the Bevy ECS doing more or less dependency injection for you (and ensuring against things like aliased mutable references), which is pretty neat.
  - keybored 4y ago
    Part of the language https://tmandry.gitlab.io/blog/posts/2021-12-21-context-capabilities/ https://tmandry.gitlab.io/blog/posts/2021-12-21-context-capa...
    - dymk 4y ago
      Fascinating. Not sure what my opinion is of it yet. Reminds me of implicit parameters in Scala - https://docs.scala-lang.org/tour/implicit-parameters.html https://docs.scala-lang.org/tour/implicit-parameters.html Edit: I think I like it. It doesn't solve dependency injection like e.g. Guice but the examples given, e.g. providing implementations for traits defined in external crates that take arbitrary state, is compelling.
fabianhjr 4y ago
Monadic functional languages have native support for dependency injection and typeclasses/interfaces provide interoperability and easy mocking or alternative implementations with type-checking / propagation of which dependency they are using. (As to avoid mismatching between mocks and a real implementation for example) https://itnext.io/hmock-first-rate-mocks-in-haskell-e59d7c3b066c https://itnext.io/hmock-first-rate-mocks-in-haskell-e59d7c3b...
- hota_mazi 4y ago
  This article is just about mocks and doesn't really touch on dependency injection at all, and Haskell simply doesn't have the mechanisms to supply the kind of implicit passing that useful DI requires.
  - jose_zap 4y ago
    Sounds like you are taking about ReaderT, which is a common way of implicitly passing more data to functions. There are many other ways, though.
    - hota_mazi 4y ago
      `Reader` and `ReaderT` are not implicit at all, they still need to pass parameters explicitly. What other ways do you have in mind? I am not aware of any Haskell functionality or compiler flag that enables implicit parameter passing, like Java, Kotlin, and Rust allow.
      - jose_zap 4y ago
        https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/implicit_parameters.html https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/impl...
sparkie 4y ago
You can do dependency injection with dynamic binding. See another post in this thread: https://news.ycombinator.com/item?id=32085346 https://news.ycombinator.com/item?id=32085346 An approach to do it statically is with implicit parameters. Scala has them, for example.

keybored 4y ago

People have written drafts of a design for this for Rust. Calling it capabilities.

dymk 4y ago
As a part of the language standard / standard library, or as a third party crate? I'm confused how this would work, as as far as I'm aware, making this a language-level feature would require significant changes to the ethos of the language. There are some examples, e.g. the Bevy ECS doing more or less dependency injection for you (and ensuring against things like aliased mutable references), which is pretty neat.
- keybored 4y ago
  Part of the language https://tmandry.gitlab.io/blog/posts/2021-12-21-context-capabilities/ https://tmandry.gitlab.io/blog/posts/2021-12-21-context-capa...
  - dymk 4y ago
    Fascinating. Not sure what my opinion is of it yet. Reminds me of implicit parameters in Scala - https://docs.scala-lang.org/tour/implicit-parameters.html https://docs.scala-lang.org/tour/implicit-parameters.html Edit: I think I like it. It doesn't solve dependency injection like e.g. Guice but the examples given, e.g. providing implementations for traits defined in external crates that take arbitrary state, is compelling.

fabianhjr 4y ago

Monadic functional languages have native support for dependency injection and typeclasses/interfaces provide interoperability and easy mocking or alternative implementations with type-checking / propagation of which dependency they are using. (As to avoid mismatching between mocks and a real implementation for example) https://itnext.io/hmock-first-rate-mocks-in-haskell-e59d7c3b066c https://itnext.io/hmock-first-rate-mocks-in-haskell-e59d7c3b...

hota_mazi 4y ago
This article is just about mocks and doesn't really touch on dependency injection at all, and Haskell simply doesn't have the mechanisms to supply the kind of implicit passing that useful DI requires.
- jose_zap 4y ago
  Sounds like you are taking about ReaderT, which is a common way of implicitly passing more data to functions. There are many other ways, though.
  - hota_mazi 4y ago
    `Reader` and `ReaderT` are not implicit at all, they still need to pass parameters explicitly. What other ways do you have in mind? I am not aware of any Haskell functionality or compiler flag that enables implicit parameter passing, like Java, Kotlin, and Rust allow.
    - jose_zap 4y ago
      https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/implicit_parameters.html https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/impl...

sparkie 4y ago

You can do dependency injection with dynamic binding. See another post in this thread: https://news.ycombinator.com/item?id=32085346 https://news.ycombinator.com/item?id=32085346 An approach to do it statically is with implicit parameters. Scala has them, for example.