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)

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 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)

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)

字符串是值类型(Strings Are Value Types)

使用字符(Working with Characters)

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)

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)

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)

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)

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")