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June 23, 2020 13:46
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| // | |
| // WalletInteractor.swift | |
| // | |
| // Tries to use an Interactor to fashion off work | |
| // against the Wallet model via delegates | |
| // | |
| // Tries to be single responsibility (?) | |
| // | |
| // Created by AD on 21/06/2020. | |
| // Copyright © 2020 AD. All rights reserved. | |
| // | |
| import Foundation | |
| // Wallet model ------------------------ | |
| struct Wallet { | |
| var cash: Int | |
| init(_ cash: Int = 0) { | |
| self.cash = cash | |
| } | |
| } | |
| // WalletInteractor code --------------- | |
| protocol WalletUseCase { | |
| var wallet: Wallet { get } | |
| var balance: Int { get } | |
| var creditDelegate: CreditUseCase? { get } | |
| var debitDelegate: DebitUseCase? { get } | |
| } | |
| protocol CreditUseCase { | |
| func credit(amount: Int) throws | |
| } | |
| protocol DebitUseCase { | |
| func debit(amount: Int) throws | |
| } | |
| protocol WalletCreditUseCase { | |
| func credit(walletHandler: WalletUseCase, amount: Int) throws | |
| } | |
| protocol WalletDebitUseCase { | |
| func debit(walletHandler: WalletUseCase, amount: Int) throws | |
| } | |
| /* | |
| * Protocol that defines the Interactor's use case. | |
| */ | |
| protocol WalletInteractorInput: class, CreditUseCase, DebitUseCase { | |
| var walletHandler: WalletUseCase? { get } | |
| var creditHandler: WalletCreditUseCase? { get } | |
| var debitHandler: WalletDebitUseCase? { get } | |
| var balance: Int { get } | |
| } | |
| class WalletHandler : WalletUseCase { | |
| private(set) internal var wallet: Wallet | |
| private(set) var creditDelegate: CreditUseCase? | |
| private(set) var debitDelegate: DebitUseCase? | |
| var balance: Int { | |
| return self.wallet.cash | |
| } | |
| init(wallet: Wallet) { | |
| self.wallet = wallet | |
| self.creditDelegate = self | |
| self.debitDelegate = self | |
| } | |
| } | |
| extension WalletHandler : CreditUseCase { | |
| func credit(amount: Int) { | |
| self.wallet.cash += amount | |
| } | |
| } | |
| extension WalletHandler : DebitUseCase { | |
| func debit(amount: Int) { | |
| self.wallet.cash -= amount | |
| } | |
| } | |
| /* | |
| * The Interactor responsible for implementing | |
| * the business logic of the module. | |
| */ | |
| class WalletInteractor : WalletInteractorInput { | |
| internal var walletHandler: WalletUseCase? | |
| internal var creditHandler: WalletCreditUseCase? | |
| internal var debitHandler: WalletDebitUseCase? | |
| var balance: Int { | |
| return walletHandler?.balance ?? 0 | |
| } | |
| init(walletHandler: WalletUseCase) { | |
| self.walletHandler = walletHandler | |
| self.creditHandler = CreditUseCaseHandler() | |
| self.debitHandler = DebitUseCaseHandler() | |
| } | |
| func credit(amount: Int) throws { | |
| guard let handler = self.walletHandler else { | |
| return | |
| } | |
| guard let creditHandler = creditHandler else { | |
| return | |
| } | |
| do { | |
| try creditHandler.credit(walletHandler: handler, amount: amount) | |
| } catch { | |
| throw error | |
| } | |
| } | |
| func debit(amount: Int) throws { | |
| guard let handler = self.walletHandler else { | |
| return | |
| } | |
| guard let debitHandler = debitHandler else { | |
| return | |
| } | |
| do { | |
| try debitHandler.debit(walletHandler: handler, amount: amount) | |
| } | |
| catch { | |
| throw error | |
| } | |
| } | |
| } | |
| // Credit Handler | |
| class CreditUseCaseHandler : WalletCreditUseCase { | |
| func credit(walletHandler: WalletUseCase, amount: Int) throws { | |
| do { | |
| if try canCredit(walletHandler: walletHandler, amount: amount) { | |
| try walletHandler.creditDelegate?.credit(amount: amount) | |
| } | |
| } | |
| catch { | |
| throw error | |
| } | |
| } | |
| func canCredit(walletHandler: WalletUseCase, amount: Int) throws -> Bool { | |
| guard amount.isPositive else { | |
| throw SpendingError.mustBePositive(amount) | |
| } | |
| return true | |
| } | |
| } | |
| // Debit Handler | |
| class DebitUseCaseHandler : WalletDebitUseCase { | |
| func debit(walletHandler: WalletUseCase, amount: Int) throws { | |
| do { | |
| if try canDebit(walletHandler: walletHandler, amount: amount) { | |
| try walletHandler.debitDelegate?.debit(amount: amount) | |
| } | |
| } | |
| catch { | |
| throw error | |
| } | |
| } | |
| func canDebit(walletHandler: WalletUseCase, amount: Int) throws -> Bool { | |
| guard amount.isPositive else { | |
| throw SpendingError.mustBePositive(amount) | |
| } | |
| let balance = walletHandler.balance | |
| guard ((balance - amount) >= 0) else { | |
| throw SpendingError.cannotSpend(amount) | |
| } | |
| return true | |
| } | |
| } |
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