From dependency injection to dependency rejection

on YouTube ↗55m

" summary

Argues that partial application in F# is equivalent to constructor injection (it compiles to a class with three fields and a constructor) but that pattern is not pure functional because it makes the whole dependency graph impure; demonstrates with a restaurant-reservation API refactor from OO MatreD + repository into F# functions and a Haskell port. Replaces indirect input/output by returning a decision (reservation option) and composing impure I/O at the edges — an impure–pure–impure sandwich — using partial application = constructor injection at IL level and separate decision (pure) from effect (impure).

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" chapters (8)

1. 0:00Introduction and setup
2. 3:44Dependency injection recap
3. 14:33Partial application in F#
4. 28:09What is a pure function?
5. 37:59Why DI isn't functional
6. 40:02Refactoring to pure functions
7. 50:32Impure pure impure sandwich
8. 53:43Summary and conclusion

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