Swift 字符串+集合(三)

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Strings and Characters 字符串和字符

String Literals 字符串字面量
用于为常量或变量提供初始值，可包含以下特殊字符
转义字符\0(空)、\\(反斜线)、\t(水平制表)、\n(换行)、\r(回车)、\"(双引号)、\'(单引号)
单字节Unicode ， 写成\xnn，nn为两位十六进制数
双字节Unicode ， 写成\unnnn，nnnn为四位十六进制数
四字节Unicode ， 写成\Unnnnnnnn，nnnnnnnn为八位十六进制数


Initializing an Empty String 初始化空字符串
[objc] view plain copy
  1. varemptyString=""//emptystringliteral
  2. varanotherEmptyString=String()//initializerSyntax
  3. //thesetwostringsarebothempty,andareequivalenttoeachother
通过检查isEmpty属性判断是否为空
    ifemptyString.isEmpty{ @H_301_82@ println("Nothingtoseehere")
  1. }
    2. @H_301_82@ //prints"Nothingtoseehere"

String Mutability 字符串的可变性
将字符串赋给变量来进行修改，或分配给常量来保证不被修改
    varvariableString="Horse" @H_301_82@ variableString+="andcarriage"
  1. //variableStringisnow"Horseandcarriage"
    2. @H_301_82@
  2. letconstantString="Highlander"
    3. @H_301_82@ constantString+="andanotherHighlander"
  3. //thisreportsacompile-timeerror-aconstantstringcannotbemodified

Strings Are Value Types 值类型
Swift的String是值类型，如果创建了一个新的字符串，当进行常量、变量赋值或在函数、方法中传递的时候都会进行值拷贝，In each case,a new copy of the existing String value is created,and the new copy is passed or assigned,not the original version.

Working with Characters 使用字符
String类型即Character字符的集合，每个字符代表一个Unicode字符，可用for-in循环来遍历字符串中的值
    forcharacterin"Dog!"{ @H_301_82@ println(character)
  1. //D
  2. //o
  3. //g
  4. //!
或者，通过标明一个Character的类型并进行赋值，可声明一个独立的字符常量或变量
    letyenSign:Character="¥"

Counting Characters 计算字符数
调用全局的countElements函数计算字符串的字符数量,(有几个表情我省略了，想知道是什么看原文)
    letunusualMenagerie="Koala,Snail,Penguin,Dromedary" @H_301_82@ println("unusualMenageriehas\(countElements(unusualMenagerie))characters")
  1. //prints"unusualMenageriehas40characters"

Concatenating Strings and Characters 连接字符串和字符
    letstring1="hello" @H_301_82@ letstring2="there"
  1. letcharacter1:Character="!"
    2. @H_301_82@ letcharacter2:Character="?"
    3. @H_301_82@ letstringPlusCharacter=string1+character1//equals"hello!"
  3. letstringPlusString=string1+string2//equals"hellothere"
    4. @H_301_82@ letcharacterPlusString=character1+string1//equals"!hello"
  4. letcharacterPlusCharacter=character1+character2//equals"!?"
    5. @H_301_82@ varinstruction="lookover"
  5. instruction+=string2
  6. //instructionnowequals"lookoverthere"
  7. varwelcome="goodmorning"
  8. welcome+=character1
  9. //welcomenowequals"goodmorning!"

String Interpolation 插值
写在括号中的表达式不能包含非转义双引号("")和反斜杠(\),回车和换行符
    letmultiplier=3 @H_301_82@ letmessage="\(multiplier)times2.5is\(Double(multiplier)*2.5)"
  1. //messageis"3times2.5is7.5"

Comparing Strings 字符串比较
String Equality 字符串相等，两个字符串完全相等，两者才相等
    letquotation="We'realotalike,youandI." @H_301_82@ letsameQuotation="We'realotalike,youandI."
  1. ifquotation==sameQuotation{
    2. @H_301_82@ println("Thesetwostringsareconsideredequal")
  2. //prints"Thesetwostringsareconsideredequal"
Prefix and Suffix Equality 前缀/后缀相等
    letromeoAndJuliet=[ @H_301_82@ "Act1Scene1:Verona,Apublicplace",
  1. "Act1Scene2:Capulet'smansion",
    2. @H_301_82@ "Act1Scene3:AroominCapulet'smansion",108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> "Act1Scene4:AstreetoutsideCapulet'smansion",248)"> "Act1Scene5:TheGreatHallinCapulet'smansion",108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> "Act2Scene1:OutsideCapulet'smansion",248)"> "Act2Scene2:Capulet'sorchard",108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> "Act2Scene3:OutsideFriarLawrence'scell",248)"> "Act2Scene4:AstreetinVerona",108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> "Act2Scene5:Capulet'smansion",248)"> "Act2Scene6:FriarLawrence'scell"
  2. ]
  3. varact1SceneCount=0
    4. @H_301_82@ forsceneinromeoAndJuliet{
  4. ifscene.hasPrefix("Act1"){
    5. @H_301_82@ ++act1SceneCount
  5. }
  6. println("Thereare\(act1SceneCount)scenesinAct1")
  7. //prints"Thereare5scenesinAct1"
  8. varmansionCount=0
  9. varcellCount=0
  10. ifscene.hasSuffix("Capulet'smansion"){
    11. @H_301_82@ ++mansionCount
  11. }elseifscene.hasSuffix("FriarLawrence'scell"){
    12. @H_301_82@ ++cellCount
  12. println("\(mansionCount)mansionscenes;\(cellCount)cellscenes")
  13. //prints"6mansionscenes;2cellscenes"

Uppercase and Lowercase Strings 大写和小写
    letnormal="Couldyouhelpme,please?" @H_301_82@ letshouty=normal.uppercaseString
  1. //shoutyisequalto"COULDYOUHELPME,PLEASE?"
    2. @H_301_82@ letwhispered=normal.lowercaseString
  2. //whisperedisequalto"couldyouhelpme,please?"




Collection Type 集合类型

Swift提供数组和字典两种集合类型来存储数据，数组按顺序存储，字典按键值对存储

Arrays 数组

创建数组
由一系列逗号分隔并由方括号包含，以下定义一个字符串类型数组，为String[]，由于Swift会自动判断所定义的变量的类型，所以String[] 也可以省略
    varshoppingList:String[]=["Eggs","Milk"]
  1. //shoppingListhasbeeninitializedwithtwoinitialitems
  2. //varshoppingList=["Eggs","Milk"]
  3. varsomeInts=Int[]()
    4. @H_301_82@ println("someIntsisoftypeInt[]with\(someInts.count)items.")
  4. //prints"someIntsisoftypeInt[]with0items."
  5. varthreeDoubles=Double[](count:3,repeatedValue:0.0)
  6. //threeDoublesisoftypeDouble[],andequals[0.0,0.0,0.0]
  7. varanotherThreeDoubles=Array(count:3,0); background-color:inherit">repeatedValue:2.5)
  8. //anotherThreeDoublesisinferredasDouble[],andequals[2.5,2.5,2.5]

访问和修改数组的值
可通过数组的方法和属性，或者下标来使用数组，等等等等，以下代码推荐使用在Xcode6下看一遍，加深体会
    println("Theshoppinglistcontains\(shoppingList.count)items.")
  1. //prints"Theshoppinglistcontains2items."
  2. ifshoppingList.isEmpty{
  3. println("Theshoppinglistisempty.")
    4. @H_301_82@ }else{
  4. println("Theshoppinglistisnotempty.")
  5. //prints"Theshoppinglistisnotempty."
  6. shoppingList.append("Flour")
  7. //shoppingListnowcontains3items,andsomeoneismakingpancakes
  8. shoppingList+="BakingPowder"
  9. //shoppingListnowcontains4items
  10. shoppingList+=["ChocolateSpread","Cheese","Butter"]
  11. //shoppingListnowcontains7items
  12. varfirstItem=shoppingList[0]
  13. //firstItemisequalto"Eggs"
  14. shoppingList[0]="Sixeggs"
  15. //thefirstiteminthelistisnowequalto"Sixeggs"ratherthan"Eggs"
  16. shoppingList[4...6]=["Bananas","Apples"]
  17. //shoppingListnowcontains6items
  18. shoppingList.insert("MapleSyrup",0); background-color:inherit">atIndex:0)
  19. //"MapleSyrup"isnowthefirstiteminthelist
  20. letmapleSyrup=shoppingList.removeAtIndex(0)
  21. //theitemthatwasatindex0hasjustbeenremoved
  22. //shoppingListnowcontains6items,andnoMapleSyrup
  23. //themapleSyrupconstantisnowequaltotheremoved"MapleSyrup"string
  24. firstItem=shoppingList[0]
  25. //firstItemisnowequalto"Sixeggs"
  26. letapples=shoppingList.removeLast()
  27. //thelastiteminthearrayhasjustbeenremoved
  28. //shoppingListnowcontains5items,andnocheese
  29. //theapplesconstantisnowequaltotheremoved"Apples"string
  30. varsixDoubles=threeDoubles+anotherThreeDoubles
  31. //sixDoublesisinferredasDouble[],2.5]

遍历数组
    foriteminshoppingList{ @H_301_82@ println(item)
  1. //Sixeggs
  2. //Milk
  3. //Flour
  4. //BakingPowder
  5. //Bananas
或者使用全局enumerate函数来对数组进行遍历，enumerate返回一个索引和一个数据值
    for(index,value)inenumerate(shoppingList){ @H_301_82@ println("Item\(index+1):\(value)")
  1. //Item1:Sixeggs
  2. //Item2:Milk
  3. //Item3:Flour
  4. //Item4:BakingPowder
  5. //Item5:Bananas

字典

字典中的数据是无须的，通过键来取数据，不同于OC中的NSDictionary 和 NSMutableDictionary可以用任意类型的对象来做键和值，Swift中必须提前声明

定义字典，airport定义为Dictionary<String,String>，意味着字典的键和值都是String类型的
    airports:Dictionary<String,String>=["TYO":"Tokyo","DUB":"Dublin"]
  1. //varairports=["TYO":"Tokyo","DUB":"Dublin"]
  2. varnamesOfIntegers=Dictionary<Int,String>()
  3. //namesOfIntegersisanemptyDictionary<Int,String>

对字典进行操作
通过字典的方法、属性和下标进行操作
    println("Thedictionaryofairportscontains\(airports.count)items.")
  1. //prints"Thedictionaryofairportscontains2items."
  2. airports["LHR"]="London"
  3. //theairportsdictionarynowcontains3items
  4. airports["LHR"]="LondonHeathrow"
  5. //thevaluefor"LHR"hasbeenchangedto"LondonHeathrow"
  6. ifletoldValue=airports.updateValue("DublinInternational",0); background-color:inherit">forKey:"DUB"){
  7. println("TheoldvalueforDUBwas\(oldValue).")
  8. //prints"TheoldvalueforDUBwasDublin."
  9. ifletairportName=airports["DUB"]{
    10. @H_301_82@ println("Thenameoftheairportis\(airportName).")
  10. else{
    11. @H_301_82@ println("Thatairportisnotintheairportsdictionary.")
  11. //prints"ThenameoftheairportisDublinInternational."
  12. airports["APL"]="AppleInternational"
  13. //"AppleInternational"isnottherealairportforAPL,sodeleteit
    14. @H_301_82@ airports["APL"]=nil
  14. //APLhasnowbeenremovedfromthedictionary
  15. ifletremovedValue=airports.removeValueForKey("DUB"){
    16. @H_301_82@ println("Theremovedairport'snameis\(removedValue).")
  16. println("TheairportsdictionarydoesnotcontainavalueforDUB.")
  17. //prints"Theremovedairport'snameisDublinInternational."


字典的遍历

    for(airportCode,airportName)inairports{ @H_301_82@ println("\(airportCode):\(airportName)")
  1. //TYO:Tokyo
  2. //LHR:LondonHeathrow
  3. forairportCodeinairports.keys{
    4. @H_301_82@ println("Airportcode:\(airportCode)")
  4. //Airportcode:TYO
  5. //Airportcode:LHR
  6. forairportNameinairports.values{
    7. @H_301_82@ println("Airportname:\(airportName)")
  7. //Airportname:Tokyo
  8. //Airportname:LondonHeathrow
  9. letairportCodes=Array(airports.keys)
  10. //airportCodesis["TYO","LHR"]
  11. letairportNames=Array(airports.values)
  12. //airportNamesis["Tokyo","LondonHeathrow"]

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