一.遍历字符串

for s in str.characters {

     print(s)

}

二.characters的数量

let str =  “你若安好"

printf(str.characters.count) = 4

let count = str.lengthOfBytesUsingEncoding(NSUTF8StringEncoding) = 12

str.utf8.count = 12

三.字符串拼接

加号拼接:let str2 = str + “便是晴天"

“\(变量名)”:print(“\(str)便是晴天")

定制字符串的拼接:

let h = 2

let m = 10

let s = 20

let strTime = String(format:”%02d:%02d:%02d”,arguments:[h,m,s]) ==> 02:23:08

四.NSString与String区别:

OC中的NSString是对象,swift中的String是结构体;

String和NSString不同,不相互兼容;

二者可以灵活转换:str as NSString转换为NSString,就任意调用OC中的方法了;

五.字符串截取:

OC方法:

let subStr = (str as NSStirng).substringWithRange(NSMakeRange())

Swift方法:

"呃呃呃饿”只是占位符,表示几个字符

letstartIndex ="呃呃呃饿".endIndex(表示4个字符)

letendIndex ="你若安好便".endIndex(表示5个字符)

//你若安好便是晴天

letswiftSubString = str2.substringWithRange(startIndex..