swift学习笔记

//常量定义
let a = "常量"
print(a,a)
print("(a)
(a)")  //换行 双引号中的
 其它常量或者变量需要加 ()

//声明常量的时候，指定常量类型
let b:Int = 0
let d:Double = 10.0
let e:String = "sss"

//swift中变量的声明
var av = "3"
var bv = av + "pinjie"   //字符串拼接
var cv = bv
print(cv)

//比较两个字符串是否相等，在swift中，指针的概念比较淡化,比较直接用等号
if(bv == cv){

    print("xiang deng")
}

//判断字符串是否为空
if e.isEmpty {

    print("字符串e是空")
}else{
    print("e不是空的")
}

//获取字符串的长度
let length = cv.characters.count
print("字符串cv的长度是",length)

//swift中的类型，没有隐式转换，只有显式转换，强制转换
var vaa = Int(d)  //double转化为int   不能把字符型转为int double
print(vaa)
print("我是(vaa)，
你是(cv)")

//插入字符
var str_var = "xiaoming"
str_var.insert("a", atIndex: str_var.startIndex.advancedBy(4));
print(str_var)

var arr:Array = ["aa",1,["aa",3.2]]
for(var i = 0; i < arr.count; i++)
{
    print(arr[i].className)
}

var int_arr = [Int32]()
//增加元素
int_arr.append(3)
int_arr.append(4)
int_arr += [2,6,7,3]

//在特定某地增加元素
int_arr.insert(12, atIndex: 1)
print(int_arr)

//移除
int_arr.removeAtIndex(1)
//int_arr.removeAll()
print(int_arr)

//开区间...
for var i in 0...arr.count-1
{
    print(arr[i])
}

//字典
//不可变
let dic:Dictionary<String,Int> = ["c":6,"a":10,"b":20]
print(dic)

//可变
var var_dic = Dictionary<String,Int>()
var_dic["age"] = 90
var_dic["age"] = 23

print(var_dic["age"])

print(var_dic)

var vdic:Dictionary = ["age":20,"name":"chang","sex":"man"]
print(vdic)

vdic.removeValueForKey("age")
print("修改后",vdic)

//遍历字典
for(key,value) in dic{

    print("遍历字典：",key,value)

}

//元组
var status_let = ("蓝欧",["iOS","123"])
var status:(classroom:String,course:Array) = status_let
var classinfo = status.0 + status.1[0] + status.1[1]
print(status.1[0])

status_let.1.insert("classroom", atIndex: 1)
print(status_let)

//分支结构中的switch

let sex = "man"
switch sex
{
case "man":
print("是man")
default:
print("0")
}

//字符串截取
var str_sub = "123400056789"
//将String转化为NSString再截取
var ns1 = (str_sub as NSString).substringFromIndex(7)
print("from截取后---",ns1)   //从index7开始到完,包括index7
var ns2 = (str_sub as NSString).substringToIndex(4)
print("to截取后---",ns2)       //从index0开始到4,不包括4
var ns3 = (str_sub as NSString).substringWithRange(NSMakeRange(4,3))
print("范围截取后---",ns3)    //从index4开始,截取三位