Swift学习之基础类型

September 20, 2015 6 分钟阅读

整型-Int
浮点数-Double
布尔-Bool
字符-Character
字符串-String
元组
集合类型-Array
集合类型-Set
集合类型-Dictionary

整型-Int

Int与UInt，其中Int是默认且推荐类型，具体长度根据编译器决定 Int8与UInt8，Int16与UInt16，Int32与UInt32，Int64与UInt64

17 //类型为Int
UInt(17) //类型为UInt
0b10001 //二进制，类型为Int
0o21  //八进制，类型为Int
0x11  //十六进制，类型为Int
Int8.max //Int8类型属性max，最大值127
Int8.min //Int8类型属性min，最小值-128

浮点数-Double

0  //类型为Double
Float(125.0)  //类型为Float
25e2 //1.25x(10^2)，Double
25e-2 //1.25x(10^-2)，Double

布尔-Bool

注意：值为true和fasle，在if和while语句判断中只能传入Bool类型

字符-Character

let aChar:Character = "a"
var bChar:Character = "\u{E9}"  //é
//疑问1，如果let aChar = "a"，那么aChar是String类型?
//疑问2，是否可写成let aChar = Character("a")

字符串-String

注意：字符串是值类型，由于uniCode码,没有确切索引位置，需要具体属性方法来索引

var empty = ""  //空字符串
var empty2 = String() //空字符串
empty.isEmpty  //属性isEmpty，是否为空字符串
var welcome = "hello"
welcome += ",world"  //此时welcome为"hello,world"
let char1:Character = "!"
welcome += char1  //此时welcome为"hello,world!"
welcome.characters //疑问：暂且认为该属性为字符数组形式
welcome.characters.count //字符数量，12
welcome[welcome.startIndex] //起始索引，"h"
welcome[welcome.startIndex.successor()] //"e"
welcome[advance(welcome.startIndex,5)] //","
welcome[welcom.endIndex] //运行时错误
welcome[welcome.endIndex.predecessor()] //末尾索引，"d"
welcome.insert(_:atIndex:)  //指定索引插入字符
welcome.splice(_:atIndex:)  //指定索引插入字符串
welcome.removeAtIndex(_:)  //指定索引删除字符
welcome.removeRange(_:)  //指定索引范围删除字符串
"abc" == "ab"  //字符串比较，返回false
"abc" != "ab"  //true
let mul = 3
let message = "\(mul) times 2.5 is \(Double(mul)*2.5)"
//"3 times 2.5 is 7.5"

for char in welcome.characters{...} //遍历各个字符

元组

1.多值复合，不要求同类型，用.0、.1访问元素

let one = (1,"One")
println("The code is \(one.0)") //访问元组，1
println("The message is \(one.1)") //One

2.元组可以分解赋值，并且可以省略部分元组值

let (oneNum,oneDesc) = one  //元组分解赋值
let (oneNum,_) = one //用下划线忽略部分元组值

3.可以给元组元素命名，用名称访问

let one2 = (num:1,desc:"One") //可以给元素命名
println("\(one2.num) -> \(one2.desc)") //用元素名访问

注意：临时结构用元组，复杂结构或使用频繁的结构用结构体或类

集合类型-Array

Array，可以简写用[T]，T为具体类型，可理解成数组

var someInts = [Int]() //Int空数组，=Array<Int>()
someInts.append(3)  //方法append,插入3
someInts = [] //空，此时不需要标注类型，可以推断
var threeDoubles = [0.0,0.0,0.0]
//等价于[Double](count:3,repeatedValue:0.0)
var sixDoubles = threeDoubles + [2.5,2.5,2.5]
//[0.0,0.0,0.0,2.5,2.5,2.5]
var shopList = ["Eggs","Milk"]
//等价于var shopList:[String] = ["Eggs","Milk"]
shopList.count //属性count，数组数据项数量
shopList.isEmpty //属性isEmpty，是否为空
shopList[0]  //"Eggs"
shopList[0] = "Six eggs"  //修改
shopList.insert("Apple",atIndex:0) //在指定位置插入元素
shopList.removeAtIndex(0) //移除指定位置元素

for item in shopList{...} //数组元素遍历
for (index,value) in shopList.enumerate(){...} //含索引遍历

集合类型-Set

Set，没有等价简写，无序不重复集合

var letters = Set<Character>() //空Set
letters.insert("a") //插入元素
letters = [] //类型确定后，可以赋值空Set
var letters:Set = ["a","b","c"]
//复杂写法，var letters:Set<Character> = ["a","b","c"]
letters.count //元素数量
letters.isEmpty //是否为空
letters.remove("b") //删除"b"，还有"a","c"
letters.contains("b") //判断是否存在某元素，false
letters.sort()  //按顺序排列

for char in letters{...} //遍历

Set基本操作

集合类型-Dictionary

Dictionary<key,Value>，可以理解成散列

var namesOfInts = [Int:String]() //空字典
nameOfInts[16] = "Sixteen" //插入或修改键值对
nameOfInts = [:] //赋值成空字典
var airports = ["YYZ": "Toronto Pearson", "DUB": "Dublin"]
//完整写法var airports: [String: String] = ["YYZ": "Toronto Pearson", "DUB": "Dublin"]
airports.count //数据项
airports.isEmpty //判断是否空
airports.updateValue(_:forkey:) //新增或修改，返回可选原值
airports["DUB"] //返回可选值，如果不存在则为nil
airports["DUB"]=nil //去掉"DUB"项
airports.removeValueForKey(_:) //去掉某项，返回可选原值

for (airportCode, airportName) in airports {//遍历
  print("\(airportCode): \(airportName)")
}

airports.keys //keys数组
airports.varlues //值数组

HarmonyHu