1 for in
for in 可用來遍歷 Array Dictionary Set Range String
for index in 1...5 {
}
for _ in 1...5 {
}
for v in [1,2,3] {
}
let numberOfLegs = ["spider": 8, "ant": 6, "cat": 4]
for (animalName, legCount) in numberOfLegs {
}
let countrys:Set = ["China", "USA", "Japan"]
for country in countrys {
}
for s in "andyron" {
}
2 while
var i = 1
while i > 10 {
// ...
i += 1
}
// repeat-while 類似其他語言的 do-while
repeat {
// ...
i += 1
} while i > 10
3 if
var temperatureInFahrenheit = 30
if temperatureInFahrenheit <= 32 {
print("It's very cold. Consider wearing a scarf.")
} else if temperatureInFahrenheit >= 86 {
print("It's really warm. Don't forget to wear sunscreen.")
} else {
print("It's not that cold. Wear a t-shirt.")
}
4 switch
不存在隱式的貫穿(No Implicit Fallthrough)，不需要break
let anotherCharacter: Character = "a"
switch anotherCharacter {
case "a", "A":
print("The letter A")
default:
print("Not the letter A")
}
// 區(qū)間匹配
let approximateCount = 62
let countedThings = "moons orbiting Saturn"
var naturalCount: String
switch approximateCount {
case 0:
naturalCount = "no"
case 1..<5:
naturalCount = "a few"
case 5..<12:
naturalCount = "several"
case 12..<100:
naturalCount = "dozens of"
case 100..<1000:
naturalCount = "hundreds of"
default:
naturalCount = "many"
}
// 元組匹配
let somePoint = (1, 1)
switch somePoint {
case (0, 0):
print("(0, 0) is at the origin")
case (_, 0):
print("(\(somePoint.0), 0) is on the x-axis")
case (0, _):
print("(0, \(somePoint.1)) is on the y-axis")
case (-2...2, -2...2):
print("(\(somePoint.0), \(somePoint.1)) is inside the box")
default:
print("(\(somePoint.0), \(somePoint.1)) is outside of the box")
}
// 值綁定(Value Bindings)
let anotherPoint = (2, 0)
switch anotherPoint {
case (let x, 0):
print("on the x-axis with an x value of \(x)")
case (0, let y):
print("on the y-axis with a y value of \(y)")
case let (x, y):
print("somewhere else at (\(x), \(y))")
}
// case分句中使用where
let yetAnotherPoint = (1, -1)
switch yetAnotherPoint {
case let (x, y) where x == y:
print("(\(x), \(y)) is on the line x == y")
case let (x, y) where x == -y:
print("(\(x), \(y)) is on the line x == -y")
case let (x, y):
print("(\(x), \(y)) is just some arbitrary point")
}
// 復合匹配
// 當多個條件可以使用同一種方法來處理時薄坏，可以將這幾種可能放在同一個case后面择浊，并且用逗號隔開。
let stillAnotherPoint = (9, 0)
switch stillAnotherPoint {
case (let distance, 0), (0, let distance):
print("On an axis, \(distance) from the origin")
default:
print("Not on an axis")
}
5 控制轉移語句(Control Transfer Statements): continue break fallthrough return throw
貫穿(Fallthrough) 執(zhí)行完一個case后刹碾，繼續(xù)向下執(zhí)行
let integerToDescribe = 5
var description = "The number \(integerToDescribe) is"
switch integerToDescribe {
case 2, 3, 5, 7, 11, 13, 17, 19:
description += " a prime number, and also"
fallthrough
default:
description += " an integer."
}
6 guard 與 if
功能類似。區(qū)別：1 guard減少嵌套座柱，會簡潔 2 解包時迷帜，guard的結果作用域不限于本身。
// greet(person: ["name": "Jane", "location": "Cupertino"])
func greet(person: [String: String]) {
if let name = person["name"] {
print("Hello \(name)!")
if let location = person["location"] {
print("I hope the weather is nice in \(location).")
} else {
print("I hope the weather is nice near you.")
}
} else {
print("Hello stranger!")
}
// print(name) //name的作用于只限于if中
}
func greet2(person: [String: String]) {
guard let name = person["name"] else {
print("Hello stranger!")
return
}
print("Hello \(name)!")
guard let location = person["location"] else {
print("I hope the weather is nice near you.")
return
}
print("I hope the weather is nice in \(location).")
}
7 檢測 API 可用性
if #available(iOS 10, macOS 10.12, *) {
// 在 iOS 使用 iOS 10 的 API, 在 macOS 使用 macOS 10.12 的 API
} else {
// 使用先前版本的 iOS 和 macOS 的 API
}
playground文件在andyRon/LearnSwift
