Hacker News new | ask | show | jobs
by fmorel 1486 days ago
Because all of our projects use Microsoft.Extensions.DependencyInjection, I make all our service classes internal

The way other projects can access these services is by using the project's helper to register them all in the DI container by their interface. That way I can be sure no one is directly using the classes and make breaking changes to the constructors (like swapping loggers or api clients), but still access them from tests.
1 comments
feoren 1485 days ago
And if you have two different DLLs that offer this pattern, but they overlap in the interfaces they register? The downstream consumer has no way of saying "I want my IFoo to be a FooA from assembly A, and my IBar to be a BarB from assembly B". And this may depend on a configuration setting! Real example: we have a bunch of useful Azure functionality in one DLL and a bunch of general useful web functionality in another; they implement many common interfaces and are alternative services you can pick depending on your deployment. But it's not as simple as "when on Azure, pick all the Azure stuff" -- it depends on which Azure services you've configured for that individual project.

If they overwrite each other, you might be able to get away with calling the god-registration-functions in the correct order (which you can determine only by reading the source code of the two functions, which are probably in different solutions), but if you really have a well mixed set of needs from A and B, this is probably not possible.

So you say: "okay, well, in this case maybe those concrete services should be public instead of internal. Obviously in this case we'd go back and do that." So your logic is: use "internal", except when it turns out we shouldn't have used it, then don't. So what purpose was it serving to begin with? None. The last lesson is that if you find yourself saying "in this case", you're actually talking about every case. That is to say: "special cases" are a symptom of a weak mental model. Good models don't have special cases.

So indeed we've identified several ways to improve, all stemming from the fact that you are using the "internal" keyword!

link