Swift_控制流
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for-in 循环
//for-in 循环
fileprivate func testForIn() {
//直接循环提取内部数据
//[1,5]
for index in 1...5 {
print("\(index) times 5 is \(index * 5)")
}
//不需要提取数据 只需要循环次数
let base = 2
let power = 3
var answer = 1
for _ in 1...power {
answer *= base
}
print("\(base) to the power of \(power) is \(answer)")
//array遍历
let array = ["XuBaoAiChiYu", "1045214799"]
for item in array {
print("array:\(item)!")
}
//Dictionary遍历
let dict = ["name":"XuBaoAiChiYu", "QQ":"1045214799"]
for (key, value) in dict {
print("key:\(key);value:\(value)")
}
/* print
1 times 5 is 5
2 times 5 is 10
3 times 5 is 15
4 times 5 is 20
5 times 5 is 25
2 to the power of 3 is 8
array:XuBaoAiChiYu!
array:1045214799!
key:name;value:XuBaoAiChiYu
key:QQ;value:1045214799
*/
}
while循环
//while循环
fileprivate func testWhile() {
//先执行while条件判断 后执行内部代码
let count = 4
var index = 0
while index < count {
index += 1
print("while:\(index)")
}
/* print
while:1
while:2
while:3
while:4
*/
}
repeat-while循环
//repeat-while循环
fileprivate func testRepeatWhile() {
//执行内部代码后判断条件
let count = 4
var index = 0
repeat {
index += 1
print("RepeatWhile:\(index)")
} while index < count
/* print
RepeatWhile:1
RepeatWhile:2
RepeatWhile:3
RepeatWhile:4
*/
}
if 判断
//if 判断
fileprivate func testIf() {
//一个条件一个条件的判断 当条件为真时 执行内部程序
let temp = 90
if temp <= 32 {
//不执行
} else if temp >= 86 {
print("执行")
} else {
//不执行
}
/* print
执行
*/
}
swich判断
//swich判断
fileprivate func testSwitch() {
//基本switch (case不会穿透)
let someCharacter: Character = "a"
switch someCharacter {
case "a":
print("1")
case "a", "b", "c":
print("2") //这里不会输出 case找到后 执行完毕就返回(如果需要穿透 加 fallthrough)
default:
print("未找到")
}
/* print
1
*/
}
switch范围选择
//switch范围选择
fileprivate func testSwitchIntervalMatching() {
//范围选择
let approximateCount = 2
switch approximateCount {
case 1..<5:
print("[1, 5)")
case 5..<10:
print("[5, 10)")
default:
print("未找到")
}
/* print
[1, 5)
*/
}
switch元组选择
//switch元组选择
fileprivate func testSwitchTuples() {
//元组选择 坐标轴测试
let random = arc4random()//随机数
let somePoint = (Int(random%3), Int(random%3))//随机数获取点
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")
}
/* print
(2, 2) is inside the box
*/
}
switch值选择
//switch值选择
fileprivate func testSwitchValueBindings() {
let random = arc4random()//随机数
//值绑定 如果设置未知数 当匹配成功时 执行此代码
let anotherPoint = (Int(random%3), Int(random%1))
switch anotherPoint {
case (let x, 0):
print("\(x)，x匹配")
case (0, let y):
print("\(y)，y匹配")
case let (x, y):
print("(\(x), \(y))，其他")
}
/* print
1，x匹配
*/
}
switch值绑定和where
//switch值绑定和where
fileprivate func testSwitchValueBindingsWhere() {
//使用where条件二次判断
let random = arc4random()//随机数
let yetAnotherPoint = (Int(random%3), Int(random%3))
switch yetAnotherPoint {
case let (x, y) where x < y:
print("\(x) < \(y)")
case let (x, y) where x > y:
print("\(x) > \(y)")
case let (x, y):
print("\(x) = \(y)")
}
/* print
1 = 1
*/
}
continue
//continue
fileprivate func testContinue() {
//跳过本次循环 继续执行下次循环
for index in 1...5 {
if index == 2 {
continue
}
print("continue:\(index)")
}
/* print
continue:1
continue:3
continue:4
continue:5
*/
}
break
//break
fileprivate func testBreak() {
// 跳过当前for或者switch 继续执行
for x in 1...5 {
if x == 2 {
break
}
print("break-x:\(x)")
}
print("break-for")
let z = 0
switch z {
case 0:
break;
default:
break;
}
print("break-switch")
/* print
break-x:1
break-for
break-switch
*/
}
fallthrough
//fallthrough
fileprivate func testFallthrough() {
//击穿：执行当前case内的代码 并执行下一个case内的代码
let x = Int(arc4random()%1)//0
switch x {
case 0:
print("0")
fallthrough
case 1:
print("1")
fallthrough
default:
break;
}
/* print
0
1
*/
}
标签
//标签
fileprivate func testLabeledStatements() {
//标签语句 可以直接跳到写标签行的代码
var b = false
go : while true {
print("go")
switch b {
case true:
print("true")
break go //跳过go标签的代码
case false:
print("false")
b = true
continue go //继续执行go标签的代码
}
}
/* print
go
false
go
true
*/
}
提前退出
//提前退出
fileprivate func testEarlyExit() {
//guard和if很像 当条件判断为假时 才执行else中的代码
func greet(_ person: [String: String]) {
guard let name = person["name"] else {
print("no name")
return
}
print("name: \(name)!")
}
greet([:])
greet(["name": "XU"])
/* print
no name
name: XU!
*/
}
检查API可用性
//检查API可用性
fileprivate func testCheckingAPIAvailability() {
if #available(iOS 9.1, OSX 10.10, *) {
print("iOS 9.1, OSX 10.10, *")
} else {
print("低版本")
}
/* print
iOS 9.1, OSX 10.10, *
*/
}
