Swift基础语法
写在前面
从今天开始学习Swift－2016-3-16；
先学习简单语法，不涉及详细API
Swift 3.0已经移除i++方法，请使用i+=1
快捷键
//格式化代码
ctrl+i
command+delete
command+/
一些琐碎
var int8:Int8
print(Int8.max)
var two = 0b111
var eight = 0o111
var sixTeen = 0x111
print("\(two) \(eight) \(sixTeen)")
var bigNum = 1_000_000
var _ = 100
var yuanzu0:(Int,String,Int,String) = (100,"0909",30,"222")
print("\(yuanzu0.1)")
var yuanzu1 = (100,"222")
print("\(yuanzu1.1)")
var yuanzu2 = (x:100,y:"aaa")
print("\(yuanzu2.x)")
var (m,_) = yuanzu2
print("\(m) ")
常量和变量
print("hello world");
let contast = 1;
print(contast)
var a:Int
a = 1000
var str = "this is a str"
var rst = "this is a rst = \(a)"
print(rst)
数组和字典
var list = [1,2,3,4,5];
print(list);
print(list[0]);
var map = ["a":1,"b":2,"c":3];
print(map);
print(map["a"])
print(map["a"]! + 100)
var shoplist = [String]()
shoplist = []
list = []
map = [:]
var emptyList = [String]()
var emptyMap = [String:Int]()
print(emptyList.count)
print(emptyMap.count)
控制流
for
let testList = [1,2,3,4,5,6,7,8];
for var i=0;i<8;i+=1 {
print("for this is \(testList[i])")
}
for x in testList{
print("for in this is \(x)")
x = 1
}
let map2scan = [
"a":[1,5],"b":["a","b","c"]
]
for (key,value) in map2scan{
print("key is \(key)")
for num in value{
print("num is \(num)")
}
}
if
var optionalStr:String? = "hello"
optionalStr = "world"
print(optionalStr == @H_283_404@nil)
var greet = "hey"
if let name = optionalStr{
greet = "hello \(name)";
}
print(greet)
if(optionalStr != @H_283_404@nil){
print("optional str is not nil")
}
if score >= 10{
}
switch
//swift支持任意数据类型的switch比较，不仅限于Int和enum
//break语句,不需要显式添加，默认语句后面都会break;
//default语句,是不可以省略的,除非所有的值都被穷举出来了；
//fallthrough语句，当满足某个case之后仍旧想使它匹配下一个case，使用 fallthrough，则不会被截断
let vegetable = "red peper"
switch vegetable{
//因为每个case之后都会有break，所以每个case之后必须至少有一行可执行语句，当需要多个匹配时，可以像下面这样
case "b","B"
print("this is b/B")
case "a":
print("this is a")
fallthrough
case let x where x.hasSuffix("peper"):
print("has suffix " + x)
default:
print("default")
}
//高级用法
//区间
let num = 100
switch num{
case 0 ..< 100:
print("小于100")
}
//元组
let point = (1,1)
switch point{
case (_,0):
print("x aliaxs");
fallthrough
case (0,_):
print("y aliaxs")
fallthrough
case (0,0):
print("origin point")
fallthrough
case (-2 ... 2,-2 ... 2):
print("near by origin point")
}
while/repeat…while
//while/repeat...while循环,当while语句成立时，语句体会执行。
var num = 0;
while num < 100{
num+=1
}
print("while num is \(num)")
repeat{
num-=1;
}while num > 0
print("repeat num is \(num)")
操作符
可选值操作符(??)
let nickName?String = "a"
let fullName = "b"
let name = "hello \(nickName ?? fullName)"
print(name)
范围操作符(..>／…)
//提供一种更简单实现循环的方式,...包含上界
//0 1 2 3
for x in 0..<4{
print("x is \(x)")
}
//0 1 2 3 4
for x in 0...4{
print("x is is \(x)")
}
强制解包操作符(!)
var num = 100
var name = "this is " + num!
简述
函数是一个可以被抽取调用的封闭代码块，是可以被传递的数据类型
//函数使用func关键字命名
//使用 [参数名:参数类型] ...的方式定义参数
//调用函数时，要用 [参数名:值] 的方式传递
//func 函数名（参数列表（参数名:参数类型））-> 返回类型 {// 函数体｝
func firstFun (name:String,pwd:String,newParams:String)->Bool {
print("name is \(name) and pwd is \(pwd)")
return true
}
firstFun("chendong",pwd:"1234567",newParams:"new params");
返回多个值
func getMultiBackFun(scores:[Int])->(max:Int,min:Int,sum:Int){
var sum = 0
var min = scores[0]
var max = scores[0]
for score in scores{
sum += score;
if(score > max){
max = score;
}
if(score < min){
min = score
}
}
return (max,min,sum)
}
let rst = getMultiBackFun([4,8,1,0,7])
print("max is \(rst.max) min is \(rst.min) sum is \(rst.sum) rst.2 is \(rst.2)")
可变长度参数函数
func changeParamFun(params :Int...)->Void{
var sum = 0;
for x in params{
sum+=x
}
print("averge is \(sum/(params.count))")
}
changeParamFun(1,4)
changeParamFun(0,9,7)
//函数可以嵌套定义,被嵌套的函数作用域有限，只能在嵌套它的｛｝中被访问，比如下面（1）中的代码是编译错误的，被嵌套的函数可以访问外面函数的变量或者全局变量，
func aOutFun@H_301_821@() -> Void{
var num = 100
func aInFun@H_301_821@()->String{
return "chendong \(num)"
}
print(aInFun())
}
aOutFun()
//1 编译错误
aInFun()
函数作为返回值
//函数作为返回值,下面的函数表示一个无参函数，返回值是一个（参数为Int,返回值是String的）函数类型，在函数returnFuncFun中定义内嵌函数并返回，在外部可以使用该函数
func returnFuncFun@H_301_821@()->(Int->String){
func INTSTRING@H_301_821@(num:Int)->String{
return "this num is \(num)"
}
return INTSTRING
}
let funINTSTR = returnFuncFun();
print("func return is \(funINTSTR(1000))")
函数作为参数传递
//函数作为参数，下面的函数表示一个参数为Int类型，一个参数为（Int->String）的函数类型，返回值String
func funParamFun@H_301_821@(num:Int,param : Int -> String)->String{
return "funparamfun + \(param(num))"
}
func paramFunc@H_301_821@(num:Int)->String{
return "paramfunc + \(num)"
}
print("rst is \(funParamFun(100,param: paramFunc))")
//结果是 rst is funparamfun + paramfunc + 100
//匿名闭包（in 前面是参数类型，in后面的是函数体）
let numbers = [1,5];
let get = numbers.map({
（in 前面是函数参数和返回值，in后面的是函数体）
@H_301_821@(number:Int)->Int in
let rst = number*2;
return 3 + rst;
})
print("rst is \(get)")
//如果一个闭包的类型已知，比如作为一个回调函数，你可以忽略参数的类型和返回值。单个语句闭包会把它语句的值当做结果返回.
numbers.map({
number in number * 3
})
//使用参数位置代指参数
numbers.sort({$0>$1})
let get2 = numbers.map({$0*2})
print("numbers is \(get2)")
