Allow using Optional dependencies about swinjectautoregistration

[paulz]

Here is how we solved injecting optionals on our project:

import Swinject
import SwinjectAutoregistration

protocol WrappingProtocol {
    associatedtype Unwrapped
    init(_ some: Unwrapped)
}

extension ImplicitlyUnwrappedOptional : WrappingProtocol {
    typealias Unwrapped = Wrapped
}

extension Optional : WrappingProtocol {
    typealias Unwrapped = Wrapped
}

postfix func ~> <Service: WrappingProtocol>(r: Resolver) -> Service {
    return Service(r ~> Service.Unwrapped.self)
}

It allow us to injection optionals, for example:

        container.storyboardInitCompleted(AccountViewController.self) { r, c in
            c.account = r~>
            c.accountManager = r~>
            c.accountUpdater = r~>
        }

[tkohout]

Hello @paulz , thanks for taking an interest in the library.

Unfortunately, it is not possible to achieve registering optional or unwrapped dependencies technically. If you look at the source you can see there are generated autoregister functions for up to 20 dependencies.

For your example with PersonOwner following function is used:

public func autoregister<Service, A, B>(_ service: Service.Type, name: String? = nil, initializer: @escaping (A, B) -> Service)

To be able to use it with optional service and unwrap it, you would also have to have

initializer: (A, B?) -> Service

But also

initializer: (A?, B) -> Service

and

initializer: (A?, B?) -> Service

This leads to large number of permutations for 20 dependencies (20!) both for Optional and ImplicitlyUnwrapped dependencies.

I also tried to cast and unwrap the dependencies in the existing functions but because we are working with types and not instances I think it is not currently possible.

[paulz]

And thank you for such an awesome pod, I've been using it on the last 3 project with the great success!

[tkohout]

I am not a big fan of adding new conformance to the native optional type. I would rather prefer solution in the Swinject itself. You can upvote this issue if you would like to have this functionality.

[paulz]

Maybe as an optional module like
SwinjectResolveOptionals

[jakubvano]

As of Swinject 2.3.0 resolution of the optional dependencies shoud work as described here, i.e

container.autoregister(PersonOwner.self, initializer: PersonOwner.init)
// or
container.register(PersonOwner.self) {  PersonOwner(name: $0~>, pet: $0~> }

Will resolve pet to an instance if there is a registration for Animal.self, or to nil if there isn't one.

This should work transparently with current vesion of SwinjectAutoregistration (provided you update the Swinject version)