Swift--基礎(二)元組 斷言 錯誤處理

元組（tuples）

把多個值組合成一個複合值。元組內的值能夠是任意類型，並不要求是相同類型

let http404Error = (404, "Not Found")

let (statusCode, statusMessage) = http404Error

print("The status code is \(statusCode)")

print("The status message is \(statusMessage)")

忽略後面的值

let (justTheStatusCode, _) = http404Error 

print("The status code is \(justTheStatusCode)")

經過下標來訪問元組中的單個元素

print("The status code is \(http404Error.0)")

能夠在定義元組的時候給單個元素命名

let http200Status = (statusCode: 200, description: "OK")

print("The status code is \(http200Status.statusCode)")

斷言

let age = -3

assert(age >= 0, "A person's age cannot be less than zero")

會致使程序的終止

錯誤處理

func makeASandwich() throws {

    // ...

}

do {

    try makeASandwich()

    eatASandwich()

} catch SandwichError.outOfCleanDishes {

    washDishes()

} catch SandwichError.missingIngredients(let ingredients) {

    buyGroceries(ingredients)

}