7.15
变量与常量
程序：计算机能理解的指令列表
变量：内容可以修改
var bianliang = 123
bianliang = 234
常量：内容不可以修改
let changliang = 123
写程序不能有歧义
数据类型 Int UInt String Float/Double
类型转换
iVal = Int(conVal)
iVal = "\(conVal)"
数据类型与集合类型
值类型与引用类型的区别
- 值类型
struct Animal {var name: String
var weight: Float}
var ani1 = Animal(name: "Cat", weight: 12)
var ani2 = ani1
ani1.name = "kitty"
修改了ani1.name,但是ani2.name不会变化
- 引用类型
class Animal {var name: String = "Cat"
var weight: Float = 12}
var ani1 = Animal()
var ani2 = ani1
ani1.name = "kitty"
虽然修改了ani1.name，但是ani2.name也会变
数组
var shuzu1 = [1, 2, 3, 4]
var shuzu2: [Int] = [1, 2, 3, 4]
var shuzu3 = [Int]_()
var shuzu4 = Array<Int>()
var shuzu5: Array<Int> = [1, 2, 3, 4]
var定义的数据可以修改内容，let定义的数组不可以修改内容
shuzu1.count #获取元素个数
shuzu1.append(5) #在末尾添加元素
shuzu1.append(contentsOf: [6, 7])
shuzu1.insert(8, at: 7) #在任意位置插入元素
shuzu1.insert(contentsOf: [9, 10], at: 0)
shuzu1.remove(at: 0) #移除元素
shuzu1.first #数组的首
shuzu1.last #数组的尾
shuzu1.removeLast()
shuzu1.removeFirst()
shuzu1.removeAll() #移除数组内的所有元素
字典
字典的创建方式
var zidian1 = ["key1":12, "key2":45]
var zidian2: [String:Int] = ["key1":12]
var zidian3 = [String:Int]()
var zidian4: Dictionary<String, Int>
var zidian5 = Dictionary<String, Int>()
字典的可用操作
zidian1["key1"] = 56 #修改key1的值
zidian1["key3"] = 78 #若是没有key3，创建赋值
zidian.removeValue(forKey: "key1")
zidian.renmoveall
