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文章插图
代表示例：
swift 3.0没有C类型的for循环了，用for in吧
开始
var str = "heal"
let num = 10
let MI_P = 3.1415926
print(MI_P)
var current = 20
print(num,current,str)
var runtoday = 5
runtoday = 6
print(runtoday)
var doubleshu:Double = 0.5
//doubleshu = 3 把这个值改成原始类型的值 为的是安全起见 防止意外的错误
//类型安全
print(doubleshu)
var isok = true
isok = false
print(isok)
如用户选填部分
形式：var 变量:类型？，默认是无值nil
var addr : String?
addr = "woshidouxindong"
print(addr ?? 0)
var num : intmax_t?
num = 1
print(num ?? 0)
var a = ""
print(a.isEmpty)//是空 true
var b = " "
print(b.isEmpty)//不是空 因为有空格 代表着某种字符
var a: Character = "我"
var b: Character = "你"
print(a)
print(b)
let words = "hellowere"
//words.characters 是把words这个句子单个拆开
for word in words.characters {
//逐个输出
print(word)
}
let a = "你"
let b = "好"
let c = "吗"
var famous = a + b + c
print(famous)//输出：你好吗
let str1: Character = "安"
let str2: Character = "迪"
famous.append(str1)
famous.append(str2)
print(famous)//输出：你好吗安迪
let name = "xiaoming"
let type = "G"
let number = 11
let price = 100.8
let message = "\(name)定了\(type)类型的\(number)票,支付\(price * 3)元"
print(message)
//输出xiaoming定了G类型的11票,支付302.4元
\0 \ \t \n \r " \\' \u{n}
let strings = "xiao\0ming\t定了\nG类型\r的11票,支付302.4\\u{n}元"
print(strings)
//1??创建一个有默认值的数组
let array : [Int]
array = [Int](repeatElement(3, count: 10))//10个元素3
print(array)
//输出的：[3, 3, 3, 3, 3, 3, 3, 3, 3, 3]
//2??创建一个有序范围的Int数组，Array(起始值...终止值)
let array2 = Array(0...100)
print(array2)
//输出
/*
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100]
*/
//3??用数组字面量来创建数组：[值1,值1,值1,...,值N]
var places = ["beijing","shanghai","guangzhou","shenzhen"]
print(places)
//输出
/*
["beijing", "shanghai", "guangzhou", "shenzhen"]
*/
//4??.1元素计数：count，空否：isEmpty
let count_arr = places.count
let empty = places.isEmpty
print(count_arr,empty)
//输出4 false
//4??.2 合并
//数组追加元素
places.append("dezhou")//追加一个元素
print(places)//输出["beijing", "shanghai", "guangzhou", "shenzhen", "dezhou"]
//数组追加数据合并为一个数组
let haiwaiPlaces = ["NewYork","london","Sao paolu"]
places += haiwaiPlaces
print(places)
//输出
/*
["beijing", "shanghai", "guangzhou", "shenzhen", "dezhou", "NewYork", "london", "Sao paolu"]
*/
//4??.3 获取元素：数组名[索引]，??索引总是从0开始的 别越界
let yuansu = places[3]
print("索引为3的值\(yuansu)")//输出:索引为3的值shenzhen
//4??.4 插入:insert
places.insert("nanjing", at: 3)

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