swift基礎3-字符串

（1）遍歷

（2）長度

（3）拼接

（4）插值

（5）大小寫

（6）trim

（7）split

……等等

var a = "你好"
var b = String()

a.isEmpty
b = "xxxxxyyyyy"
b.isEmpty

//遍歷
for c in b {
    println(c)
}

//計算長度
countElements(b)

//拼接
a += b

//插值
var strss = "a: \(a), b: \(b)"

//比較
let str_a = "abc"
let str_b = "abc"
str_a == str_b

//字典序比較
let str_c = "abd"
str_b < str_c

//前後綴
str_b.hasPrefix("a")
str_b.hasSuffix("c")

//大小寫轉換
str_b.uppercaseString
str_b.lowercaseString

//每個單詞首字母大寫
let str_d = "i am a good person"
str_d.capitalizedString

//trim操作

var s1 = "  xx  xx "
s1.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceCharacterSet())
s1.stringByTrimmingCharactersInSet(NSCharacterSet(charactersInString:" "))

//split操作

var s2 = "i am a good boy"
s2.componentsSeparatedByString(" ")
s2.componentsSeparatedByCharactersInSet(NSCharacterSet(charactersInString: "a "))