1.For-in循环中...
for index in 1...5 {
print("(index) times 5 is (index * 5)")
}
for _ in 1...5 {
可以用下划线忽略当前值
}
2.字典通过元祖返回
3.do while循环变成repeat
repeat {
statements
} while condition
4.switch不需要break
let someCharacter: Character = "z"
switch someCharacter {
case "a":
print("The first letter of the alphabet")
case "z":
print("The last letter of the alphabet")
default:
print("Some other character")
}
5.switch case的body不能为空
6.case可以带区间
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"
}
print("There are (naturalCount) (countedThings).")
7.case的元祖表示
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")
}
8.case加额外条件
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")
}
9.case fallthrough贯穿
fallthrough关键字不会检查它下一个将会落入执行的 case 中的匹配条件。fallthrough简单地使代码继续连接到下一个 case 中的代码
10.while加标签
gameLoop: while square != finalSquare {
diceRoll += 1
if diceRoll == 7 { diceRoll = 1 }
switch square + diceRoll {
case finalSquare:
// diceRoll will move us to the final square, so the game is over
break gameLoop
case let newSquare where newSquare > finalSquare:
// diceRoll will move us beyond the final square, so roll again
continue gameLoop
default:
// this is a valid move, so find out its effect
square += diceRoll
square += board[square]
}
}
print("Game over!")
11.guard与if的区别
像if语句一样，guard的执行取决于一个表达式的布尔值。我们可以使用guard语句来要求条件必须为真时，以执行guard语句后的代码。不同于if语句，一个guard语句总是有一个else从句，如果条件不为真则执行else从句中的代码。
guard let name = person["name"] else {
return
}
12.检测 API 可用性
Swift内置支持检查 API 可用性，这可以确保我们不会在当前部署机器上，不小心地使用了不可用的API。
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
}
在它一般的形式中，可用性条件使用了一个平台名字和版本的列表。平台名字可以是iOS，macOS，watchOS和tvOS——请访问声明属性来获取完整列表。除了指定像 iOS 8的主板本号，我们可以指定像iOS 8.3 以及 macOS 10.10.3的子版本号。