【swift 学习】第二课---类型转换,类型别名,元祖,可选类型,可选绑定，断言

import Foundation//1.类型转换let a:Int8 = 10let b:Int16 = 100print("\(Int16(a) + b)")let sa = 3let pi = 3.1415let add = Double(sa) + piprint(add)//类型别名 typealias AudioSample = UInt16var maxValue = AudioSample.minprint(maxValue)//3.元祖let people = (18,"xiaoming")let (age,name) = peopleprint("The age is \(age)")print("THe name is \(name)")//分解的时候要忽略的部分用_表示 还可以通过下表来去除元祖中元素的值let (age2,_) = peopleprint(age2)print(people.1)//定义元祖的时候， 给单个元素命名let rec = (w:10,h:20)print("\(rec.w)")print(rec.h)//4.可选类型：处理值可能缺失的情况let Str = "1234"let converNumber = Int(Str)//这里 在swift 2.0中String.toInt()已经重命名为Int（String）print(converNumber)//这里输出为Optional（1234）意思是 是Optional Int 或者 Int？if converNumber != nil{    print(converNumber!)//可选值得强制解析 输出 1234}//可选绑定：可以用在if和while语句中来对可选类型的值进行判断并把值赋给一个常量或者变量。if let actualNumber = Int(Str){    print(actualNumber)}var severCode:Int? = 404severCode = nil //现在severCode 不包含值var sunny:String?//隐式解析可选类型：第一次被赋值之后，可以确定一个可选类型总会用值var possibleStr:String! = "adfads"print(possibleStr)//5.断言let age3 = -10assert(age3 >= 0,"年龄要大于0")//程序运行到这里会报错！！