Yeah, I find DI really scary. It practically shifts the complexity elsewhere, out of the programming language and program, and into configuration and classloading magic, that you may eventually discover at runtime.
I think I would prefer languages to embark proper abstractions for that. Scala has implicits which are not as refined as some DI frameworks I’m sure, but do the job in practice. In general, there should be a way for programs to delineate portions of code that expose/depend on certain capabilities (use a database, or more generally run asynchronous, frees its own memory, is a pure calculation), and this is an avenue being researched in capabilities-based languages.
I hear your concerns about DI frameworks and I agree it would be preferable if their config could somehow be validated at compile time instead of runtime. That being said, in my experience, runtime issues are fairly rare. Some DI frameworks even provide a simple method you can call at runtime to validate config at startup. Furthermore, you can use the DI pattern without a framework— design your classes accordingly, then create and inject the dependencies yourself instead. The point is to program against abstractions to make your code more testable, and while a framework can automate away some of the bookkeeping, you can dispense with using a framework for any of a number of valid reasons.
So, what would you do instead in this case, use a DI framework to pass the
Databasecapability around?(Edit: I do realize the answer is likely to be language dependent)
That would be a good solution most of the time, yes
Yeah, I find DI really scary. It practically shifts the complexity elsewhere, out of the programming language and program, and into configuration and classloading magic, that you may eventually discover at runtime.
I think I would prefer languages to embark proper abstractions for that. Scala has implicits which are not as refined as some DI frameworks I’m sure, but do the job in practice. In general, there should be a way for programs to delineate portions of code that expose/depend on certain capabilities (use a database, or more generally run asynchronous, frees its own memory, is a pure calculation), and this is an avenue being researched in capabilities-based languages.
I hear your concerns about DI frameworks and I agree it would be preferable if their config could somehow be validated at compile time instead of runtime. That being said, in my experience, runtime issues are fairly rare. Some DI frameworks even provide a simple method you can call at runtime to validate config at startup. Furthermore, you can use the DI pattern without a framework— design your classes accordingly, then create and inject the dependencies yourself instead. The point is to program against abstractions to make your code more testable, and while a framework can automate away some of the bookkeeping, you can dispense with using a framework for any of a number of valid reasons.
Yes, that’s pretty much always the correct answer for passing dependencies.