Swift学习日记001

学习的网站：https://www.raywenderlich.com  （这里面有swift示例代码，还有对应知识点的练习）

学习环境：  xcode－playground iOS9 swift2

本人初学swift,下面的代码示例均出自https://www.raywenderlich.com ，写的不对的地方欢迎各位朋友指正

代码如下

import UIKit//var 变量 let 常量var str = "Hello, playground"var myVariable = 42myVariable = 50let myConstant = 42//输出相当于oc NSLogprint(myVariable+myConstant)//let **: type = **  指定类型的初始化，对应上面没有type的swift会根据你赋的初值自动判断类型let life: Int = 42let pi: Double = 3.14let canTouchThis: Bool = falselet captain: String = "Kirk"let myFavoriteNumber: Int = 7//var luckyNumber: Int = 7var luckyNumber = 7let batman = 10var superman = 9var aquaman = 1batman<aquamansuperman>=8batman==(aquaman+superman)batman>aquaman&&batman==(aquaman+superman)batman<superman||aquaman<supermanvar spiderman = 7//if else语句if (batman>spiderman){    spiderman = spiderman-1}else if (batman>=spiderman){    spiderman = spiderman-1;}else{    spiderman = spiderman+1;}var appleCount = 5//字符串中输出变量格式为 \(var)print("Sally has \(appleCount) apple")var JohnGrade = 95var SamGrade = 85if (JohnGrade<SamGrade){    print("JohnGrade is less than SamGrade")}else if (JohnGrade==SamGrade){    print("JohnGrade is equal to SamGrade")}else{    print("JohnGrade is greater than SamGrade")}var secondsLeft = 3while (secondsLeft>0){    print(secondsLeft)    secondsLeft = secondsLeft-1}print("Blast off")var donutsCount = 5var eatNumber = 0while (donutsCount>0){    eatNumber += 1    print("Cop eat \(eatNumber) donuts")    donutsCount = donutsCount-1}print("You are all out of donuts :(")var numbers = 0while(numbers <= 10)  {    if(numbers == 9)  {        numbers = numbers + 1        continue    }    print(numbers)    numbers = numbers + 1}var optionalNumber : Int? = 5optionalNumber = nilif let thisNumber = optionalNumber{    print("It's a number")}else{    print("It's not a number")}var laLearned: String = "three"var laLearnedNum: Int? = (Int)(laLearned)if let num = laLearnedNum  {    print("It is a number")}else  {    print("It is not a number")}