Swift初级：变量与数据类型

//: Playground - noun: a place where people can playimport UIKit//1.第一个程序var str = "Hello, playground"println("Hello,swift!")//2.let 常量constants， var 变量variableslet webSiteName:String = "www.baidu.com"var 整型:Int = 10let bignum_a = 1000000let bignum_b = 1_000_000let bignum_c = 1_0000_0000var 浮点型64:Double = 10.0,浮点型32:Float = 10.0var red,green,blue:Double//强制类型转换let integer_a:Int = 3let double_b:Double = 0.1415926let pi = Double(integer_a) + double_b//3.布尔类型以及if语句let imtureVar:Bool = truelet imfalseVar:Bool = falseif imtureVar {    println(imtureVar);}else{    println(imfalseVar);}//4.Tuples 元组let  registerResult = (isRegisterSuccess:true,nickname:"慕课女神",gender:"女")//遍历元组1let (isRegisterSuccess,nickname,gender) = registerResultisRegisterSuccessnicknamegender//遍历元组2registerResult.0registerResult.1registerResult.2//遍历元组3registerResult.isRegisterSuccessregisterResult.nicknameregisterResult.gender//使用下划线（_）忽略部分数值let  connectionResult : (Bool , Int , String) = (true , 404 , "Not Found")let (isLoginSuccess,_,_) = connectionResultif(isLoginSuccess){    println("登录失败！！！")}//5.可选型Optionals：或者是一个值，或者是没有值nilvar a:Int?a = 12let userInput = "18"var age = userInput.toInt()if(age != nil){    println("your age is \(age)");    println("your age is \(age!)");//一定是有值的，安全的,即可选型的解包    println("your age is " + String(age!));}else{    println("Invalidate userInput");}//Optional Bindingif let userAge = userInput.toInt(){    println("your age is \(userAge)");}else{    println("Invalidate userInput");}//可选型let strName:String? = "test"strNamestrName!let strB:String! = "test"strB