005-Swift3.0之控制语句

一、循环语句

1.for-in循环

1）遍历区间操作符

for index in 1...5 {
    let value = index * 5
    print("\(index) * 5 = \(value)")
}

2）使用下划线忽略每一项的值

let a = 3
let n = 10
var sum = 0
for _ in 1...n {
    sum += a
}

3）遍历数组

let names = ["Frank0", "Frank1", "Frank2", "Frank3", "Frank4", "Frank5",]
for name in names {
    print(name)
}

4）遍历字典

let students = ["0": "Frank0", "1": "Frank1", "2": "Frank2", "3": "Frank3"]
for (id, name) in students {
    print("学号：\(id)，姓名：\(name)")
}

2.while循环

var p = 0
while p < 3 {
    print(p)
    p += 1
}

3.repeat-while

var q = 0
repeat {
    print(q)
    q += 1
} while q < 3

 

二、条件判断语句

1.if语句

let x = 10
let y = 2
if x < y {
    print("x < y")
} else if x == y {
    print("x = y")
} else {
    print("x > y")
}

2.switch语句

1）case匹配多个值

let someCharacter: Character = "c"
switch someCharacter {
case "a":
    print("The first letter of the alphabet")
case "b", "c", "d":
    print(someCharacter)
case "z":
    print("The last letter of the alphabet")
default:
    print("Some other character")
}

2）case匹配区间

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"
}

3）case匹配元祖

let somePoint = (1, 1)
switch somePoint {
case (0, 0):
    print("somePoint在坐标原点上")
case (_, 0):
    print("somePoint在x轴上")
case (0, _):
    print("somePoint在y轴上")
case (-2...2, -2...2):
    print("somePoint在以坐标原点为圆心，上下左右延伸2个坐标范围内")
default:
    print("somePoint在其他区域")
}

4）case匹配值绑定

let anotherPoint = (2, 0)
switch anotherPoint {
case (let x, 0):
    print("anotherPoint在x轴上，x = \(x)")
case (0, let y):
    print("anotherPoint在y轴上，y = \(y)")
case let (x, y):
    print("anotherPoint在象限内，x = \(x)，y = \(y)")
}

5）case中使用关键字where添加额外判断条件

let yetAnotherPoint = (1, -1)
switch yetAnotherPoint {
case let (x, y) where x == y:
    print("yetAnotherPoint在直线y=x上，x = \(x)，y = \(y)")
case let (x, y) where x == -y:
    print("yetAnotherPoint在直线y=-x上，x = \(x)，y = \(y)")
case let (x, y):
    print("yetAnotherPoint在其他直线上，x = \(x)，y = \(y)")
}

 

三、控制转移语句

1.continue 退出本次循环

2.break  退出循环

3.fallthrough 贯穿

let scroe = 90
switch scroe {
case 0...59:
    print("不及格")
case 60...100:
    print("及格")
    fallthrough    // 匹配到当前case后，会继续往下匹配
case 80...100:
    print("高分")
default:
    print("其他")
}

4.return 提前退出

5.throw