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Swift中的字符串和集合

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字符串和字符

表现形式

var dollarSign: Character = "$"
var myFirstSwiftString: String = "mo' money"
var mySecondSwiftString: String = "mo' problems"
var concatenatedString = myFirstSwiftString + ", " + mySecondSwiftString

//显示其类型
concatenatedString.dynamicType

遍历字符串中的字符数组

var password = "Meet me in St. Louis"
for character in password.characters {
if character == "e" {
    print("found an e!")
} else {
}
}

字符串中取值字符

尾字符

var lastLetter = word.removeAtIndex(word.endIndex.predecessor())

首字符

var firstLetter = word.removeAtIndex(word.startIndex)

将字符串转成数组，取出第一个

var word = "tan"
var firstLetter = Array(word.characters)[0]

字符串

表现形式

纯字符串

var s:Character = "美"
var quote1 = "\'"
var quote2 = "\u{22}"

带变量的字符串

print("quote1的值为:\(quote1),quote2的值为:\(quote2)")

带表达式的字符串

var lbsPerDay = 0.75
var daysPerMonth:Double = 30.0
doggyDiet = "\(dogName) eats \(lbsPerDay * daysPerMonth)lbs of dog food per month"

Swift中的字符串是结构体，而NSString中的字符串是Class.Swift中的字符串也可以使用NSString方法

let newPassword = password.stringByReplacingOccurrencesOfString("e", withString: "3")
  1. 单个字符来指定字符常量，如“A”，“9”
  2. 转义字符表示特殊字符常量，如”\n”,”\t”
  3. 使用\u{n}的Unicode形式，n代表一个1~8位的十六进制
  4. 必须用双引号包起来
  5. Swift中的每一个字符代表了一个可扩展字母集

字符串创建

方法1：直接赋值

var str1 = "Jike"

方法2：构造函数

var str2 = String()

//创建多个重复字符的字符串
var str3 = String(count:4,repeatedValue:Character("a"))
var strRep = String(count:4,repeatedValue:UnicodeScalar("xxxxx")) //使用unicode
print(strRep)

初始化空字符串

// Here's one way to initialize an empty Swift string
var characterPoorString = ""

// And here's another 
let potentialRichString = String()
characterPoorString.characters

字符串是否为空

print(str3.isEmpty)

字符串拼接

方式1.用 “+”

var str4 = str1 + "College"
str1 += "Hello"
print(str4)

方式2.用append

let char:Character = "!"
str1.append(char)
print(str1)

字符数量

Swift1.x

print("str3 has \(countElements(str3)) characters")

Swift2.x

print("str3 has \(str4.characters.count) characters")

这两种的输出结果不一样

var nWithTilde = "\u{006E}\u{0303}"
nWithTilde.unicodeScalars.count
nWithTilde.characters.count  //通常用这个
  1. Swift中的Unicode16Count函数所获得的值，才是和NSString中的length一样。因为SWIFT的count是基于Unicode，而OC的length是基于UTF-16
  2. Swift中的字符串是否可以修改仅通过定义的是变量还是常量来决定,也就是var or let

字符串比较

let quotation = "We are the same"
let sameQuotation = "We are the same"
if quotation == sameQuotation {
print("These are the same")
}

字符串是否有特定的前缀后缀

var food = ["Fruits:apple",
"Fruits : orange",
"Fruits : banana",
"Vegetables: tomato",
"Vegetables: potato"]

for fry in food{
if fry.hasPrefix("Fruits"){
   print(fry)
}

if fry.hasSuffix("o"){
   print(fry)
}
}

字符串是否包含某子字符串

let word = "fortunate"
if word.rangeOfString("tuna") != nil {
print("yes")
}

替换子字符串

let lottaLikes = "If like, you wanna learn Swift, like, you should build lots of small apps, cuz it's like, a good way to practice."

let noLikes = lottaLikes.stringByReplacingOccurrencesOfString("like, ", withString: "")

字符串转为整形

Swift 1.x

let myString: String = "256"
let myInt: Int? = myString.toInt()

Swift 2.x

let myString: String = "256"
let myInt: Int? = Int(myString)

字符串大小写转换

let didYouKnowString = "Did you know that the Swift String class comes with lots of useful methods?"
let whisperString = "psst" + ", " + didYouKnowString.lowercaseString

集合

1

数组

数组的创建

方式1

var numbers = Array<Double>() //Array<Double>.init 后面省略了init方法

方式2

var moreNumbers = [Double]()
moreNumbers = [85.0, 90.0, 95.0]

方式3

let differentNumbers = [97.5, 98.5, 99.0]

数组合并

moreNumbers = moreNumbers + differentNumbers

数组可持有任何类型对象

var circuit = [livingRoomSwitch, kitchenSwitch, bathroomSwitch]

数组尾部添加

var roadTripMusic = ["Neil Young","Kendrick Lamar","Flo Rida", "Nirvana"]
roadTripMusic.append("Rae Sremmurd")

数组插入

roadTripMusic.insert("Dej Loaf", atIndex: 2)

数组删除

roadTripMusic.removeAtIndex(3)

数组计数

roadTripMusic.count

数组取值

let musician = roadTripMusic[2]

数组替换

food[0...2] = ["a","b"]
//从第一个到第三个元素进行替换，但只有两个元素，第三个将被删除，被“没有”所替换

数组删除最后一项

food.removeLast()

数组删除所有

food.removeAll(keepCapacity:false)

字典

字典创建

方式1

var groupsDict = [String:String]()

方式2

var animalGroupsDict = ["whales":"pod", "geese":"flock", "lions": "pride"]

var averageLifeSpanDict = [String:Range<Int>]()
var lifeSpanDict = ["African Grey Parrot": 50...70, "Tiger Salamander": 12...15, "Bottlenose Dolphin": 20...30]

空字典

var emptyDic:[String:Double] = [:] 
print(emptyDic.isEmpty)

字典添加

animalGroupsDict["crows"] = "murder"
animalGroupsDict["monkeys"] = "troop"

字典计数

animalGroupsDict.count

字典删除

animalGroupsDict["crows"] = nil

移除单个值

person.removeValueForKey("name")

移除所有值

person.removeAll(keepCapacity:false)

字典更新

方式1

animalGroupsDict["monkeys"] = "barrel"

方式2:返回值为optional类型，如果该key存在，则赋新值，返回old value,如果key不存在，则赋值，同时返回nil

var group = animalGroupsDict.updateValue("gaggle", forKey: "geese")

字典取值

字典取值所返回的是optional，因为很可能没有该key，所以使用前需要用if let unwrap

let groupOfWhales = animalGroupsDict["whales"]

if let groupOfWhales = animalGroupsDict["whales"] {
print("We saw a \(groupOfWhales) of whales from the boat.")
} else {
print("No value found for that key.")
}

字典键和值的取出

let keysArr = [String](person.keys)
let valueArr = [String](person.values)
print(valuesArr)

字典的遍历

字典的遍历后，返回时元组类型

for (key,value) in person{
 print("\(key):\(value)")
}

字典的使用

这种的声明是不严谨的，因为值的类型都不是一样的，系统会推断它是NSObject类型

字典的key or value 通常最好是同一类型，否则强制解析时会出错

var person = ["age":18,"name":"Tom","身高":178]

这样会报错，因为是将NSObject转为int

var height:Int? = person["身高"]  
if height != nil {
   print(height!)
}

以下才正确

var person = ["age":"18","name":"Tom","身高":"178"]

var height:String? = person["身高"]  
if height != nil {
   print(height!)
}

print(person["age"])

Set - 无序且不能有相同的元素

集合创建

方式1

var utensils = Set<String>()
var trees = Set<Character>()
var flowers:Set<Character> = ["🌷","🌹","🌸"]

方式2

var cutlery: Set = ["fork", "knife", "spoon"]

集合的操作

trees.insert("🌲")
trees.insert("🌳")
trees.insert("🌵")
trees.remove("🌵")
trees.count

AnyObject and Any

Swift中有两种特殊的object:

  1. Any:表示任何数据类型
  2. AnyObject:表示任何对象
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3
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    //因为数组里的数据不一样，这里的数组默认是AnyObject类型，因为他们都不一样
    var shoppingList = ["Eggs",123,true] 
    for item in shoppingList {
      print(item)
}
for fruit in food{
fruit = "good" //error, fruit默认是let类型
}