Swift循环语句和条件判断语句

for循环

Swift提供了两种for循环语句,一种是C语言的for循环:条件递增,这种方式在SWift3.0中遗弃了,现在Swift主要推荐for-in循环

//在for-in语句中,..<符号表示数组范围0~10之间,但是并不包含10,如果循环中包含10,可以使用...10
for index in 0..<10 {
    
    print("index:\(index)")
}


//循环遍历数组
let names = ["小明","小红"]

for index in names {
    
    print("name:\(index)")
}

//遍历元组
let yuanz = [(12,"age"),(13,"age")]
for index in yuanz {
    
    print("name:\(index.0)")
}

//遍历字典
var dic=["name":"小明","age":"12"]
for index in dic {
    
     print("index:\(index)")
}

while循环语句

Swift的while循环语句,和OC的while语句非常的相似,用于重复执行某个代码块

var index = 0

while index<5
{
    index+=1
    print("index:\(index)")
}

repeat-while循环语句(do-while语法一致)

var a=0
repeat
{
    a+=1
    print("a:\(a)")
}
while a<5

if条件判断语句

if(3<4){
    print("呵呵")
}

switch条件判断语句

let time = 10

switch time {
case 9:
     print("这是9")
case 10:
     print("这是10")
case 11,12,14:
     print("这是毛线")
    
    
default:
      print("这是毛线")
}

continue语句

for index in 0...10 {//打印的结果是没有3的
    
    if index==3 {
        
        continue
    }
    print("index:\(index)")
    
}

fallthrough语句

通过该语句，可以允许Swift代码在执行完一个case分支后,调到下一个case中

let age = 10

switch age {
case 9:
    print("这是9")
    fallthrough
case 10:
    print("这是10")
    fallthrough
case 11,12,14:
    print("这是毛线")
    
default:
    print("这是毛线")
}