7.15

變量與常量

程序：計算機(jī)能理解的指令列表

變量：內(nèi)容可以修改

var bianliang = 123

bianliang = 234

常量：內(nèi)容不可以修改

let changliang = 123

寫程序不能有歧義

數(shù)據(jù)類型 Int UInt String Float/Double

類型轉(zhuǎn)換

iVal = Int(conVal)
iVal = "\(conVal)"

數(shù)據(jù)類型與集合類型

值類型與引用類型的區(qū)別

1. 值類型

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不會變化

2. 引用類型

class Animal {var name: String = "Cat"
var weight: Float = 12}
var ani1 = Animal()
var ani2 = ani1
ani1.name = "kitty"

雖然修改了ani1.name，但是ani2.name也會變

數(shù)組

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定義的數(shù)據(jù)可以修改內(nèi)容，let定義的數(shù)組不可以修改內(nèi)容

shuzu1.count                     #獲取元素個數(shù)

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                     #數(shù)組的首

shuzu1.last                      #數(shù)組的尾

shuzu1.removeLast()

shuzu1.removeFirst()

shuzu1.removeAll()               #移除數(shù)組內(nèi)的所有元素

字典

字典的創(chuàng)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 #若是沒有key3，創(chuàng)建賦值

zidian.removeValue(forKey: "key1")

zidian.renmoveall