Should a DI framework be handling which implementa...

# android-architecture

[dave08]

Should a DI framework be handling which implementation to give for each platform, or should that always be delegated to a factory method?

[Colton Idle]

platform as in... api level? or platform as in kotlin multiplatform, platform?

[dave08]

I have a bunch of criteria, one is api level, versions of other related apps... Webview version... On one hand the DI IS a type of factory, on the other it doesn't seem too SRP to let it decode these things. Where should the line be drawn?

[K Merle]

Can't DI function returning an object be a factory method? It's not mutually exclusive.

[dave08]

Yeah, the thing is that DI frameworks aren't so testable, so when there's a bit more logic... but then what's the point of DIs?

[gildor]

I believe all this logic should be encapsulated to a factory and DI could just call this factory to create an instance, so you will be able to test this logic

[gildor]

So it’s like Merle suggested, but instead of injecting factory, you inject actual instance

[dave08]

Oooh, I missed that, using the DI to pass the FACTORY METHOD... I thought he meant the DI's method IS the factory method... and your point @gildor, is a good one, you win the best of both worlds...

I once thought it was taboo to actually run something in DI, that it's only to passively create valid objects, and running a factory is also running something, but I guess you're right they probably complete each other in this case.

Thanks!

[gildor]

Using a factory from DI looks exactly the same for me as using constructor from DI

[dave08]

So you really only use DI to rig things together but NOT to RESOLVE which implementations to give?

[dave08]

Or are there exceptions?

[gildor]

I personally do not have such cases when I need to provide different implementation on runtime, usually it's solved on compile time for me (different apps/components require different implementation and it encoded on level of DI, so resolved on compile time (with dagger)), but if I would have such case I would extract it to some factory as suggested above

[gildor]

running a factory is also running something

It's also true for constructor, you run init of this method, factory is like a "constructor" for an interface
Also you can use another class as a facade for other implementation and just delegate to those platform specific implementation, if you don't want to have explicit factory

[dave08]

Interesting, thanks!