本篇内容介绍了“如何理解swift错误处理”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！
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//错误处理
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做错误处理
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? 如果抛出错误，程序不会崩溃，会返回nil
func someThrowingFunction() throws -> Int {
//
return 1
}
let x = try? someThrowingFunction()
//等价
let y: Int?
do {
y = try someThrowingFunction()
} catch {
y = nil
}如果错误真的发生，会得到运行时错误
//try! 中断错误传播，如果错误真的发生，会得到运行时错误 let photo = try! someThrowingFunction()
//指定退出前的清理动作 defer 关键字
func processFile(filename: String) throws {
if exists(filename) {
let file = open(filename)
defer {
close(file)
}
while let line = try file.readline() {
//
}
//
}
}“如何理解swift错误处理”的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识可以关注创新互联网站，小编将为大家输出更多高质量的实用文章！
