Swift Either for handling mock data from Remote Api

SomeController.swift

class SomeController {
      private func loadOfferSummaries() -> Void {
        api.fetchOfferSummaries( { either in
            switch either {
            case let .Failure(boxedError):
                NSLog("Failure fetching games, code --> \(boxedError.value.code)")
                // mock out test data
                self.offers = self.mockOfferSummaries()
                self.loadTable()
            case let .Success(boxed):
                self.offers = boxed.value
                NSLog("Fetched \(self.offers.count) offer summaries from server")
                self.loadTable()
            }
        })
    }
    
    private func mockOfferSummaries() -> OfferSummaries {
        let outDeal = AirOutSummary(id: 1, deal: "Better Seat?")
        let inDeal = AirInSummary(id: 2, deal: "Free Drinks?")
        let hotelDeal = HotelSummary(id: 3, deal: "Nicer Room?")
        return [outDeal, hotelDeal, inDeal]
    }
}