Day07:For - in循环

• For - in循环

1. 使用for - in 循环遍历序列，比如一个范围的数字，数组中的元素或者字符串中的字符。

• For - in循环遍历字典

1. 当字典遍历时，每一个元素都返回一个（key,value）元组，你可以在for-in循环中使用显式命名常量来分解（key,value）元组成员。
2. 如果不需要序列的每一个值，你可以使用下划线来取代遍历名以忽略值。

• For-in 分段区间

1. 使用stride（from：to：by）函数来跳过不想要的标记（开区间）。

• 闭区间也同样使用，使用stride（from:through:by）即可。 
• Repeat - while 循环（Object-C do-while）。 

• 【代码演示】 

import UIKit//1、for in 遍历区间
for index in 0...3{
print(index)//结果：0、1、2、3
}//2、for in 遍历字符
for c in "hellow" {print(c)//结果：h、e、l、l、o、w
}
//3、for in 遍历数组
let names = ["mary","jack","yoke"]
for name in names {print(name)//结果：mary、jack、yoke
}//4、for in 遍历字典let dicValue = ["city_1":"shanghai","city_2":"xian","city_3":"beijing"]for dict in dicValue {print("key is \(dict.key) value is \(dict.value)")/** 结果：key is city_2 value is xiankey is city_1 value is shanghaikey is city_3 value is beijing*/
}for (key,value) in dicValue{print("key is \(key) value is \(value)")/** 结果：key is city_2 value is xiankey is city_1 value is shanghaikey is city_3 value is beijing*/
}//5、for in 区间for i in stride(from: 0, to: 6, by: 2){
print(i)//结果 0 2 4
}for i in stride(from: 0, through: 6, by: 2){
print(i)//结果 0 2 4 6
}