03-流程控制

//流程控制1-20
//1. if 后的条件可以省略小括号 且条件只能是Bool  let age = 4 if age {} 这样是错的
let age = 4
if age >= 22 {
    print("married")
} else if age >= 18 {
    print("being adault")
} else if age >= 7 {
    print("go to school")
} else {
    print("just a child")
}

//2. while
var num0 = 5
while num0 > 0 {
    print(num0)
    num0 -= 1 //不用 num-- swift去掉了++ --可读性差
}

//3.repeat-while 相当于 do-while
var num1 = -1
repeat {
    print(num1)
} while num1 > 0 //打印1次

//4.for 闭区间运算符 a...b  a<= 取值 <=b

let names = ["aa", "bb", "cc", "dd"]
for i in 0...3 {
    print(names[i])
}

let range = 1...3
for i in range {
    print(names[i])
}

//i默认是let 如有需要可以声明为var
for var i in 1...3 {
    i += 5
    print(i)
}

//i 没用到可以忽略
for _ in 1...3 {
    print("for" )
}

let a = 1
var b = 2
for i in a...b {
    print(names[i])
}

for i in a...3 {
    print(names[i])
}

//5.半开区间运算符 a..<b  a<=取值<b
for i in 1..<5 {
    print(i)
}

//for区间运算符用在数组上
for name in names[0...3] {
    print(name)
}

//6.单侧区间:让区间朝一个方向尽可能的远
for name in names[2...] {//实际是2...3 即>=2
    print("-\(name)") //-cc -dd
}

for name in names[...2] {//实际是0...2 即<=2
    print(name)
}

for name in names[..<2] {//实际是0..<2 即<2
    print("*\(name)")
}

let range0 = ...5
range0.contains(7)
range0.contains(-3)

//7.区间类型
let range1:ClosedRange<Int> = 1...3
let range2:Range<Int> = 1..<3
let range3:PartialRangeThrough<Int> = ...5
//8.字符、字符串也能使用区间运算符，但默认不能用在for-in中
let stringRange1 = "cc"..."ff" //ClosedRange<String> cc cd ce cf dc dd de df ec ed ee ef fc fd fe ff
stringRange1.contains("cb")//f
stringRange1.contains("dz")//t
stringRange1.contains("fg")//f

let stringRange2 = "a"..."f"
stringRange2.contains("d")//t
stringRange2.contains("h")//f
//\0-~囊括了所有可能用到的ASCII字符 说明Character 否则默认是字符串
let characterRange:ClosedRange<Character> = "\0"..."~"
characterRange.contains("G")//t

//9.带间隔的区间值
let hours = 11
let hourInterval = 2
//t取值: 从4开始，累加2，不超过11 从几到几间隔几
for t in stride(from: 4, through: hours, by: hourInterval) {
    print(t)//4 6 8 10
}


//10.case default 后不能写大括号
var number0 = 1
switch number0 {
case 1:
    print("number is 1")
    break
case 2:
    print("number is 2")
    break
default:       //必须保证处理所有情况 如果去掉default会报错
    print("number is other")
    break
}

//11.如果保证已处理所有情况，也可不必使用default
enum Answer {case right,wrong}
let answer = Answer.right
switch answer {
case Answer.right:
    print("right")
case Answer.wrong:
    print("wrong")
}
//12.由于已确定answer是Answer类型，因此可以省略Answer
switch answer {
case .right:
    print("right")
case .wrong:
    print("wrong")
}


//13.默认可以不写break，并不会贯串到后边的条件,使用fallthrough可以贯串
var number1 = 1
switch number1 {
case 1:
    print("number is 1")
    fallthrough
case 2:
    print("number is 2")
default: //case Default 后边至少要有一条语句，如果不想做任何事情加个break即可
    break
} //number is 1  number is 2




//14.复合条件 switch 也支持Character String类型
let string = "Jack"
switch string {
case "Jack":
    fallthrough
case "Rose":
    print("right person")
default:
    break
}
//也可以
switch string {
case "Jack", "Rose":
    print("Right person")
default:
    break
}
//15.注意字符串 字符声明区别
let character:Character = "a"
switch character {
case "a", "A":
    print(" a A ")
default:
    print("not a or A ")
}

//16.区间匹配、元组匹配
let count = 62
switch count {
case 0:
    print("none")
case 1..<5:
    print("few")
case 5..<12:
    print("several")
case 12..<100:
    print("dozens of")
case 100..<1000:
    print("handreds of")
default:
    print("many")
}//dozens of

//_忽略值 case匹配属于模式匹配
let point = (1,1)
switch point {
case (0,0):
    print("the origin")
case (_,0):
    print("on the x")
case (0,_):
    print("on the y")
case (-2...2,-2...2):
    print("inside the box")
default:
    print("outside the box")
}//inside the box

//17.值绑定
let point1 = (2,0) //也可var
switch point1 {
case (let x, 0):
    print("on the x with an x value of \(x)")
case (0, let y):
    print("on the y with a y value of \(y)")
case let (x, y):
    print("some where else at (\(x), \(y)")
}//on the x with an x value of 2
 
//18. where 用于switch
let point2 = (1, -1)
switch point2 {
case let (x, y) where x == y:
    print("on the line x == y")
case let (x, y) where x == -y:
    print("on the line x == -y")
case let (x, y):
    print("(\(x), \(y)) is just some arbitrary point")
}//on the line x == -y

//19.使用where是来过滤num 是continue 不是 break,将所有正数加起来
var numbers = [10, 20, -10, -20, 30, -30]
var sum = 0
for num2 in numbers where num2 > 0 {
    sum += num2
}
print(sum)//60

//20.标签语句:说白了就是标志结束哪个循环
outer: for i in 1...4 {
    for k in 1...4 {
        if k == 3 {
            continue outer
        }
        if i == 3 {
            break outer
        }
        print("i == \(i), k == \(k)")
    }
}
/*
 i == 1, k == 1
 i == 1, k == 2
 i == 2, k == 1
 i == 2, k == 2
 */