1 for in for in 可用来遍历 Array Dictionary Set Range String 1 2 3 4 5 6 7 8 9 10 11 12 13 14 for index in 1...5 { } for _ in 1...5 { } for v in [1,2,3] { } let numberOfLegs = ["spider": 8, "ant": 6, "cat": 4] for (animalName, legCount) in numberOfLegs { } let countrys:Set = ["China", "USA", "Japan"] for

Collection 分为 Arrays, Sets, Dictionaries(Collection，Sets有时都翻译成集合) 1 数组(Arrays)是有序数据的集。 一个数组中只能有一

1 字符串字面量(String Literals) “Some string literal value” 2 初始化空字符串 (Initializing an Empty String) 1 2 3 4 5 var emptyString = "" var anotherEmptyString = String() if emptyString.isEmpty { print("Nothing to see here") } 3 字符串可变性(String Mutability) 1 2 3

1 赋值运算符(Assignment Operator) 赋值操作并不返回任何值 1 2 3 let b = 10 var c = 5 let (x, y) = (2, 5) 2 算术运算符(Arithmetic Operators) 1 2 3 4 5 6

1 常量和变量(Constants and Variables) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 // 声明：常量 let 变量 var let constants = 10 var variables = 0 // 多个声明 var x = 0.0, y = 0.0, z = 0.0