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本篇內(nèi)容介紹了“如何理解swift錯(cuò)誤處理”的有關(guān)知識(shí),在實(shí)際案例的操作過(guò)程中,不少人都會(huì)遇到這樣的困境,接下來(lái)就讓小編帶領(lǐng)大家學(xué)習(xí)一下如何處理這些情況吧!希望大家仔細(xì)閱讀,能夠?qū)W有所成!
//錯(cuò)誤處理 enum VendingMachineError: Error { case invalidSelection case insufficientFunds(coinsNeeded: Int) case outOfStock } struct Item { var price: Int var count: Int } class VendingMachine { var inventery = [ "Candy Bar": Item(price: 12, count: 7), "Chips": Item(price: 10, count: 4), "Pretzels": Item(price: 7, count: 11) ] var coinsDeposited = 0 func vend(itemNeed name: String) throws { guard let item = inventery[name] else { throw VendingMachineError.invalidSelection } guard item.count > 0 else { throw VendingMachineError.outOfStock } guard item.price <= coinsDeposited else { throw VendingMachineError.insufficientFunds(coinsNeeded: item.price - coinsDeposited) } coinsDeposited -= item.price var newItem = item newItem.count -= 1 inventery[name] = newItem print("show \(name)") } } let favoriteSnacks = [ "Alice": "Chips", "Bob": "Licorice", "Eve": "Pretzels" ] func buyFavoriteSnack(person: String, vendingMachine: VendingMachine) throws { let snackName = favoriteSnacks[person] ?? "" try vendingMachine.vend(itemNeed: snackName) } //使用Do-Catch做錯(cuò)誤處理 var vendingMachine = VendingMachine() vendingMachine.coinsDeposited = 8 for p in favoriteSnacks { do { try buyFavoriteSnack(person: p.key, vendingMachine: vendingMachine) print("\(p.key) success!") } catch VendingMachineError.invalidSelection { print("\(p.key) Invalid Selection") } catch VendingMachineError.outOfStock { print("\(p.key) Out of stock") } catch VendingMachineError.insufficientFunds(let coinsNeeded) { print("\(p.key) need insert an additional \(coinsNeeded) coins.") } catch { print("Unexpected error:\(error).") } }
//try? 如果拋出錯(cuò)誤,程序不會(huì)崩潰,會(huì)返回nil func someThrowingFunction() throws -> Int { // return 1 } let x = try? someThrowingFunction() //等價(jià) let y: Int? do { y = try someThrowingFunction() } catch { y = nil }
如果錯(cuò)誤真的發(fā)生,會(huì)得到運(yùn)行時(shí)錯(cuò)誤
//try! 中斷錯(cuò)誤傳播,如果錯(cuò)誤真的發(fā)生,會(huì)得到運(yùn)行時(shí)錯(cuò)誤 let photo = try! someThrowingFunction()
//指定退出前的清理動(dòng)作 defer 關(guān)鍵字 func processFile(filename: String) throws { if exists(filename) { let file = open(filename) defer { close(file) } while let line = try file.readline() { // } // } }
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