003 Swift3 0之字串型別

一、空字串

var emptystring1 = ""

var emptystring2 =string()
//判斷是否為空
ifemptystring1.isempty

二、字串可變性

1.常量字串(let宣告的字串)完成賦值之後不可變

2.變數字串(var宣告的字串)可變

var varstring = "

hello
"varstring += "
, frank
"let letstring = "
highlander"//
letstring += "frank" (報錯，不可變)

三、字串的值型別

在swift中，字串的賦值和傳值都是進行重新拷貝乙份，因此它是值型別，僅僅只是拷貝值而已，是獨立存在的

四、字串&字元

1.屬性：characters

var string1 = "

hello, frank
"for character in
string1.characters

2.字元的宣告

注意：字元的宣告必須顯式宣告，否則系統會誤認為是string型別

let c1: character = "!"

var c2: character = "
h"

3.字元轉化為字串

①通過字串初始化函式

let character: character = "s"

let characterarray: [character] = ["
f", "
r", "
a", "
n", "
k", "
c", "
o", "
m", "
e", "
o", "
n", "!"
]let str1 = string(character); //
字元轉字串
let str2 = string(characterarray) //
字符集轉字串

②通過連線運算子

let s1 = "

hello
"let s2 = "
frank
"var s3 = s1 +s2
let s4 = "
welcome
"var s5 = "
to huanggang
"s5 += s4

let cc: character = "!"

let ss = "hg"
var ss1 = "
welcome to huanggang
"

④任意基本資料型別通過\()轉化為字串

let ccc: character = "m"

let nnn = 27
let mmm = 169.10
let sss = "
frank
"let s = "
\(ccc)y name is \(sss), i'm \(nnn) years old! my height is \(mmm) cm.
"

五、字串的字元數量

let sss1 = "

koala 
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