参考书：
The Swift Programming Language
The Swift Programming Language 中文版
软件版本：
OS X Yosemite 10.10.3
Xcode 6.3.2
Swift 1.2
标签：
Swift 编程学习笔记

字符串和字符(Strings and Characters)

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字符串字面量(String Literals)

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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 换行符：\n
   1.5 回车符：\r
   1.6 双引号："
   1.7 单引号：'
   1.8 Unicode标量：\u{n}，n为任意的一到八位十六进制数

println("\0")
println("\\")
println("\t")
println("a\n")
println("a\r")
println("\"")
println("\'")
println("\u{1F496}") //1F496，即一个十六进制数

代码示例

初始化空字符串(Initializing an Empty String)

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1. 给变量附上空值

var emptyString = ""

2. 初始化一个String实例

var anotherEmptyString = String()

3. String类中，有isEmpty属性，可以判断字符串是否为空，isEmpty为Boolean类型

字符串可变性(String Mutability)

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字符串是值类型(Strings Are Value Types)

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使用字符(Working with Characters)

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1. 声明时标注一个Character类型，可以建立一个独立的字符常量或者变量

let yenSign:Character = "¥"

计算字符数量(Counting Characters)

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1.调用全局count() 函数

let unusualMenagerie = "Koala 🐨, Snail 🐌, Penguin 🐧, Dromedary 🐪"
println("unusualMenagerie has \(count(unusualMenagerie)) characters")

计算 unusualMenagerie 中的字符数量

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

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1. 用+运算对字符串进行拼接

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

2. 用+=将一个字符串添加到一个已经存在的字符串变量上

var instruction = "look over"
instruction += string2

3. 用append()方法将一个字符添加到字符串变量的尾部

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

比较字符串(Comparing Strings)

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1. 字符串相等，==直接判断

let quotation = "我们是一样一样滴."
let sameQuotation = "我们是一样一样滴."
if quotation == sameQuotation {
    println("这两个字符串被认为是相同的")
}

2. 前缀/后缀相等，调用字符串的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
    }
}

大写和小写字符串(Uppercase and Lowercase Strings)

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1. 调用字符串的uppercaseString或者lowercaseString属性实现

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

Unicode

Unicode 中每一个字符都可以被解释为一个或多个 unicode 标量。 字符的 unicode 标量是一个唯一的21位数字(和名称)，例如U+0061表示小写的拉丁字母A ("a")，U+1F425表示小鸡表情 ("🐥")

Swift能够以三种(?)Unicode兼容的方式访问字符串的值：

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 标量 (Unicode Scalars)

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