參考書：
The Swift Programming Language
The Swift Programming Language 中文版
軟件版本：
OS X Yosemite 10.10.3
Xcode 6.3.2
Swift 1.2
標簽：
Swift 編程學習筆記

字符串和字符(Strings and Characters)

字符串字面量(String Literals)

1. 特殊字符
   1.1 空字符：\0
   1.2反斜杠：\
   1.3 水平制表符：\t
   1.4 換行符：\n
   1.5 回車符：\r
   1.6 雙引號："
   1.7 單引號：'
   1.8 Unicode標量：\u{n}，n為任意的一到八位十六進制數

println("\0")
println("\\")
println("\t")
println("a\n")
println("a\r")
println("\"")
println("\'")
println("\u{1F496}") //1F496，即一個十六進制數

代碼示例

初始化空字符串(Initializing an Empty String)

1. 給變量附上空值

var emptyString = ""

2. 初始化一個String實例

var anotherEmptyString = String()

3. String類中，有isEmpty屬性，可以判斷字符串是否為空，isEmpty為Boolean類型

字符串可變性(String Mutability)

字符串是值類型(Strings Are Value Types)

使用字符(Working with Characters)

1. 聲明時標注一個Character類型，可以建立一個獨立的字符常量或者變量

let yenSign:Character = "￥"

計算字符數量(Counting Characters)

1.調用全局count() 函數

let unusualMenagerie = "Koala ??, Snail ??, Penguin ??, Dromedary ??"
println("unusualMenagerie has \(count(unusualMenagerie)) characters")

計算 unusualMenagerie 中的字符數量

連接字符串和字符(Concatenating Strings and Characters)

1. 用+運算對字符串進行拼接

let string1 = "Hello"
let string2 = " there"
var welcome = string1 + string2

2. 用+=將一個字符串添加到一個已經存在的字符串變量上

var instruction = "look over"
instruction += string2

3. 用append()方法將一個字符添加到字符串變量的尾部

let exclamationMark:Character = "!"
welcome.append(exclamationMark)

比較字符串(Comparing Strings)

1. 字符串相等，==直接判斷

let quotation = "我們是一樣一樣滴."
let sameQuotation = "我們是一樣一樣滴."
if quotation == sameQuotation {
    println("這兩個字符串被認為是相同的")
}

2. 前綴/后綴相等，調用字符串的hasPrefix()或者hasSuffix()方法

let romeoAndJuliet = [
    "Act 1 Scene 1: Verona, A public place",
    "Act 1 Scene 2: Capulet's mansion",
    "Act 1 Scene 3: A room in Capulet's mansion",
    "Act 1 Scene 4: A street outside Capulet's mansion",
    "Act 1 Scene 5: The Great Hall in Capulet's mansion",
    "Act 2 Scene 1: Outside Capulet's mansion",
    "Act 2 Scene 2: Capulet's orchard",
    "Act 2 Scene 3: Outside Friar Lawrence's cell",
    "Act 2 Scene 4: A street in Verona",
    "Act 2 Scene 5: Capulet's mansion",
    "Act 2 Scene 6: Friar Lawrence's cell"
]
var act1SceneCount = 0
for scene in romeoAndJuliet {
    if scene.hasPrefix("Act 1 ") {
        ++act1SceneCount
    }
}
println("There are \(act1SceneCount) scenes in Act 1")
var mansionCount = 0
var cellCount = 0
for scene in romeoAndJuliet {
    if scene.hasSuffix("Capulet's mansion") {
        ++mansionCount
    } else if scene.hasSuffix("Friar Lawrence's cell") {
        ++cellCount
    }
}

大寫和小寫字符串(Uppercase and Lowercase Strings)

1. 調用字符串的uppercaseString或者lowercaseString屬性實現

import Foundation
let normal = "Could you help me, please?"
let shouty = normal.uppercaseString
let whispered = normal.lowercaseString

Unicode

Unicode 中每一個字符都可以被解釋為一個或多個 unicode 標量。 字符的 unicode 標量是一個唯一的21位數字(和名稱)，例如U+0061表示小寫的拉丁字母A ("a")，U+1F425表示小雞表情 ("??")

Swift能夠以三種(?)Unicode兼容的方式訪問字符串的值：

1. UTF-8

for codeUnit in dogString.utf8 {
    print("\(codeUnit) ")
}
print("\n")

2. UTF-16

for codeUnit in dogString.utf16 {
    print("\(codeUnit) ")
}
print("\n")
// 68 111 103 33 55357 56374

3. Unicode 標量 (Unicode Scalars)

for scalar in dogString.unicodeScalars {
    print("\(scalar.value) ")
}
print("\n")