1 //: Playground - noun: a place where people can play  2   3 import UIKit  4 /*********常量与变量的声明**********/  5 let a = 5 //定义常量  6 //a = 6  //常量不能修改  7 var b = 5  8 b = 6  9 //swift中所有的基本类型都是值类型，包括string类型 10 var c = b 11 c 12 b = 88 13 c 14 //swift中的类都是大写的 15 //下面的常量声明是显式指定类型 16 let i: Float = 5.5 //默认编译器推断的是double 17  18 //常用的类型string,character,bool,float,double,int 19  20 let flag = true 21  22 let str = "hello world" 23 let ch: Character = "a" 24  25 //元祖(tuple) 26 //元祖声明的语法就是一个括号，逗号分隔用来存放多个数据 27 let t = (404,"not found") 28 let t1 = (1,1,1,2,3,4) 29 //通过下标来访问元祖 30 t.0 31 t.1 32  33 let t2 = (name: "CJ" ,age: 35.5)//不需要给每个成员都取名字 34  35 t2.name 36 t2.age 37 let t3: (name: String,age: Float) = ("cj2",46.6) 38 t3.age 39 t3.name 40  41 let t4: (String,Float) = ("aaaa",4) 42 t4.0 43 t4.1 44  45 let t5:(name: String, Float) = ("bbb",5) 46 t5.1 47  48 let t6:(String,Float) = (name: "xxxx",age: 55) 49 t6.0 50 t6.1 51 //t6.name //由于在声明的时候没有指定名字，所以不能访问 52  53 //下面的写法（声明的同时就赋值）不行， 54 //let t8: (name: String = "aaa",age: Float = 222) 55  56 //string类型 57  58 let str1: String 59  60 str1 = "aaaa" 61  62 var  str2   = "bbbb" 63 str2 = "cccc" 64 str2 += "dddd" 65 str2 = "abcdefg" 66  67 str2.characters.count //取字符长度 68  69 str2.startIndex 70 str2.endIndex 71 str2[str2.startIndex] 72 //str2[str2.startIndex + 1] 73  74 str2.index(after: str2.startIndex) 75 str2[str2.index(after: str2.startIndex)] 76 str2.index(before: str2.endIndex) 77  78 str2.index(str2.startIndex, offsetBy: 3) 79 str2[str2.index(str2.startIndex, offsetBy: 3)] 80  81 str2.index(str2.endIndex, offsetBy: -3) 82  83 str2.substring(to: str2.index(str2.startIndex, offsetBy: 3)) 84  85 str2.substring(from: str2.index(str2.startIndex, offsetBy: 3)) 86  87 str2.uppercased() 88 str2.lowercased() 89 str2.capitalized 90  91 str2.hasPrefix("abc") //是否有前缀（prefix） 92 str2.hasSuffix("abc") //是否有后缀 93 str2.hasSuffix("g") 94 str2.hasSuffix("fg") 95 str2.contains("de") // 是否包含 96  97 i 98  99 let str3 = "abc \(i * 5)"100 101 //swift操作符基本与c#，java一样102 103 let f = true104 a105 106 if f {107     print("true")108 }109 110 if (a >= 5 )  {111     print("da yu dengyu 5")112 }  else if( a > 3) {113     114 } else {115     116 }117 118 let age = 35119 switch age {120 case 25:121     print("25sui")122 case 35:123     print("chenjun")124 default:125     print("fei 25")126 }127 128 Int.min129 Int.max130 131 switch age {132 case 1...60:133     print("suo you de zhengshu ")134 default:135     print("1...60zhiwai")136 }137 138 139 switch age {140 case 1,20,35,60:141     print("suo you de zhengshu ")142 default:143     print("1...60zhiwai")144 }145 146 147 let arr = [1,2,3,4,8,30,5,10]148 for a in arr {149     print(a)150 }151 152 153 for a in 0...3 {154     print(arr[a])155 }156 157 var max = arr[0]158 for item in arr {159     if item % 2 != 0 && item > max {160         max = item161     }162 }163 max164 165 var n = 3166 while n < 10 {167     n += 1168     print(n)169 }170 171 n = 3172 repeat {173     print("xxx")174      n += 1175 } while  n < 10176 177 178 /********  集合 Array，Dictionary，Set ***/179 180 let arr2: Array<Int> = Array<Int>()181 var arr3 = [1,2,3,3]182 let arr4: Array<Int> = []183 184 185 arr3[0]186 187 arr3.append(5)188 arr3.append(contentsOf: [6,7,8])189 arr3190 arr3 += [10,11]191 arr3192 193 //arr3.insert(contentsOf: <#T##Collection#>, at: <#T##Int#>)194 195 //arr3.remove(at: <#T##Int#>)196 197 198 var dic = ["a":"abc","b":"def"]199 dic["a"]200 dic["c"] = "ggg"201 dic.count202 203 for k in dic.keys {204     print(k)205 }206 207 for v in dic.values {208     print(v)209 }210 211 for (k,v) in dic {212     print ("key is \(k) value is \(v)")213 }214 215 216 var s: Set<Int> = [1,2,3,4,4]217 218 s.count219 s.insert(2)220 221 s.count222 223 var s1: Set<Int> = [2,3,6,7]224 225 let r1 = s.intersection(s1)226 s.union(s1)227 228 229 230 /*作业231  1.求出一个字符串中从第三个字符后的所有子字符串232  2.求出一个数组中所有偶数的和233  3.求出两个Set的差234  4.["127":[40,80,90],"130":[60,70,80]]这个字典代表2个班级所有的成绩，求出两个班级的平均分，结果用tuple表示，比如（70，70）235  236  额外需要学习的237  1.找出trim方法238  2.学习switch没有讲的内容239  240  241  24