medium_post_002

SomeSignInService.swift

class SomeSignInService: SignInService {

    init() {
        // do whatever the provider needs to be set up
    }

    func signIn(_ completion: @escaping (String?) -> Void) {
        // call the sign in service and receive a token
        completion(token)
    }

    func signOut() { /* ... call the provider's sign out */ }
}